Speaker 1: Get in touch with technology with tech Stuff from how
Speaker 1: stuff works dot com. Hey there, and welcome to tech Stuff.
Speaker 1: I am your host, Jonathan Strickland. I'm a senior writer
Speaker 1: with how stuff Works dot com, where we attempt to
Speaker 1: demystify the universe for your education and entertainment. My specialty
Speaker 1: happens to be technology despite my degree in medieval and
Speaker 1: Renaissance English literature. So we're gonna talk about some pretty
Speaker 1: high tech stuff today. Actually, I'm gonna look at a
Speaker 1: topic that we first addressed way back in two thousand
Speaker 1: and eleven with the episode how Lasers Work. That's when
Speaker 1: Chris Pallette, my original co host, and I sat down
Speaker 1: and we talked about a little bit of the history
Speaker 1: of lasers and how they actually operate. But I thought
Speaker 1: it would be better to revisit this, explain it again,
Speaker 1: kind of take a different approach to it. Um. So,
Speaker 1: lasers are awesome and they can do tons of different stuff. Right.
Speaker 1: We can do everything from having a little laser pointer
Speaker 1: to amuse ourselves and our pets, to having a laser
Speaker 1: element inside optical drive so that we can read information
Speaker 1: that's been stored on a disc. Two communications satellites, to
Speaker 1: propelling spacecraft to cutting steel. There's all sorts of things
Speaker 1: we can do with lasers. Oh, we can threaten our enemies.
Speaker 1: We can tie them up and put them on a
Speaker 1: slab and then slowly have a laser creep upward and
Speaker 1: then laugh maniacally as we expect Mr Bond to die.
Speaker 1: We can do all that sort of stuff with lasers.
Speaker 1: So we're gonna talk about what they are, what they
Speaker 1: can do, their history, and maybe some cool trivia about
Speaker 1: lasers as well, and laser related stuff. So let's get
Speaker 1: to it now. First of all, what is the technical
Speaker 1: definition of a laser? Well, laser is an acronym that
Speaker 1: means that it's a word that's made up of the
Speaker 1: initials of other words, right, so it stands for light
Speaker 1: amplification by stimulated emission of radiation. But for most of
Speaker 1: us that doesn't really clear things up. That just raises
Speaker 1: other questions like what do they mean by stimulated emission
Speaker 1: of radiation? And how do you amplify light? So I'm
Speaker 1: gonna go in talk about all of that kind of
Speaker 1: stuff because it's really fascinating and involves a lot of
Speaker 1: science and technology, two things I love to talk about.
Speaker 1: The third thing, obviously being Chaucer's Canterbury tails one that
Speaker 1: applicated with the shoulder at SUTA, but that does not
Speaker 1: really fit with lasers. They didn't have the lasers tail,
Speaker 1: so we're gonna skip Canterbury Tails for this episode. Now,
Speaker 1: a laser is a device that produces a very narrow
Speaker 1: beam of light, and these beams are monochromatic. That means
Speaker 1: they are single colors see single wavelength. That's a very
Speaker 1: specific wavelength of light for each laser and us a
Speaker 1: specific color. So we perceive different wavelengths of light as
Speaker 1: different colors of light. So if you think of your
Speaker 1: roy g BIV, that is actually a a spectrum literally
Speaker 1: a spectrum of colors. That's also a spectrum of wavelengths,
Speaker 1: with red being the longest wavelength and violet being the
Speaker 1: shortest wavelength in the visible spectrum. Uh, the wavelength of
Speaker 1: light depends entirely on the amount of energy electrons release
Speaker 1: within the laser itself. So electrons release energy and in
Speaker 1: the form of photons or light particles, and the color
Speaker 1: of laser you get depends upon the amount of energy
Speaker 1: those electrons are releasing, and the amount of energy they
Speaker 1: release is dependent upon the type of atoms that they
Speaker 1: are connected to, because it all has to do with
Speaker 1: orbits of electrons around nuclei. More on that in a second.
Speaker 1: So the light is also coherent. Now, that does not
Speaker 1: mean it is able to hold a conversation and make
Speaker 1: salient points. It's not that kind of coherent. It means
Speaker 1: that the light is made up of organized photons. Organized
Speaker 1: botons in this case means that they're all traveling the
Speaker 1: same pattern of wavelength that are all in the same
Speaker 1: page as it were. If you look at wavelength, if
Speaker 1: you were to draw a series of waves, they would
Speaker 1: all be lined up exactly, so all the crests and
Speaker 1: the troughs would be lined up along the same points.
Speaker 1: At any point along the wavelength, they would match entirely.
Speaker 1: So that that is what we mean by coherent. It's
Speaker 1: what helps keep the light organized and moving in that
Speaker 1: specific direction you wanted to. And the light is also directional.
Speaker 1: That means the beam is tight and concentrated and remains
Speaker 1: so over great distances. You don't get a lot of
Speaker 1: uh light diverging from that that pathway, and some lasers
Speaker 1: are able to project for miles and miles, like hundreds
Speaker 1: of thousands of miles in some cases or uh without
Speaker 1: having any kind of degradation of the beam, which is
Speaker 1: kind of cool. I mean, it's amazingly cool. Now you
Speaker 1: contrast that with something like a flashlight. Flashlights have a
Speaker 1: beam that spreads out as it travels outward from its source,
Speaker 1: it diffuses, so it's different from a laser. It doesn't
Speaker 1: have the coherence that a laser would have. Um this
Speaker 1: is typical of most light sources. You don't find lasers
Speaker 1: in nature. Lasers are something that we have caused to
Speaker 1: happen because of the natural laws. If it weren't for
Speaker 1: the natural laws, lasers wouldn't work. Obviously, we didn't create
Speaker 1: that out of whole cloth. But it doesn't spontaneously happen
Speaker 1: in nature because you have to have very specific parameter
Speaker 1: set up in order to generate a laser beam. Now,
Speaker 1: to understand why it works the way it does, it
Speaker 1: helps to know how light works, and a light behaves
Speaker 1: both as a wave and a particle. But for this
Speaker 1: bit of the explanation, we're mostly concerned with wave physics,
Speaker 1: even though we'll be talking about photons, the basic unit
Speaker 1: of light, the basic particle of light. A lot in
Speaker 1: this episode. So a light source gifts off waves of light,
Speaker 1: and different colors of light have different wavelengths. Like I said, uh,
Speaker 1: you know, those red wavelengths are longer than the orange ones.
Speaker 1: Infrared waves are even longer, Ultra violet are even shorter
Speaker 1: than violet. So you've got that that different spectrum of
Speaker 1: wavelengths there. When you get down to that violet, you're
Speaker 1: really looking at the shortest wavelengths that we can perceive
Speaker 1: before it just becomes invisible to us. So again, ultra violet,
Speaker 1: we can't see that um Certain classes and dungeons and
Speaker 1: dragons different They can see ultraviolet light, not the rest
Speaker 1: of us. So these waves travel typically out of phase
Speaker 1: from each other from normal light sources. So again, if
Speaker 1: you were to chart those wavelengths, the crests and valleys
Speaker 1: would of each individual photon wouldn't match up right, like
Speaker 1: the crest of one might be matched with the valley
Speaker 1: of another or somewhere else along its wavelength. They wouldn't
Speaker 1: be moving in phase, they'd be out of phase. So
Speaker 1: lasers all line up those light waves at the same
Speaker 1: way so that they are in phase. And that's what
Speaker 1: we mean when we say coherent. That the various photons
Speaker 1: are all in phase with one another, and the way
Speaker 1: you generate lasers makes this happen. Uh, it's kind of cool.
Speaker 1: We'll talk about that again a little bit later. But
Speaker 1: all the photons in the beam have unified wave fronts,
Speaker 1: so they're all moving in exactly the same wavelength a
Speaker 1: exactly the same time. Now, to understand how all of
Speaker 1: this works, it takes. It takes a looking at atoms.
Speaker 1: We have to go back to basic science. So let's
Speaker 1: take a look at an atom. Now. Back in the
Speaker 1: day when I was in school, atoms were depicted as
Speaker 1: being kind of like the orbits of planets, where you
Speaker 1: would have a nucleus in the center, kind of like
Speaker 1: the sun, and electrons would orbit a neat little circles
Speaker 1: around at specific distances from the nucleus. As it turns out,
Speaker 1: things aren't quite so neat and simple. Atrons are in
Speaker 1: an electron cloud that are around the nucleus. It is
Speaker 1: impossible to say with complete certainty, Uh, where an electron
Speaker 1: is at any given moment. You know, you can know
Speaker 1: a position of an electron, but not it's direction or
Speaker 1: vice versa with complete certainty. Heisenberg's and certainty principles is
Speaker 1: a fun thing. But you know, when you have a
Speaker 1: basic atom and you haven't added any energy to the atom,
Speaker 1: it's and it's ground state energy level. That's when it's
Speaker 1: just you know, kind of chilling. Atoms are always in motion. Uh.
Speaker 1: You only get atoms in no motion at all at
Speaker 1: absolute zero, when you're at zero kelvin. That is when
Speaker 1: you have zero atomic movement. But otherwise, atoms are always
Speaker 1: in motion, even in solid objects, they're just not moving
Speaker 1: a lot. When you add energy to atoms, they move more.
Speaker 1: They start to get energized. When you energize atoms enough,
Speaker 1: you can boost them to an excited level. Now, typically
Speaker 1: you do this by applying energy like heat, light or
Speaker 1: electricity to the atom. Uh, Whereas if you want to
Speaker 1: excite me, you just say, hey, they might be giants
Speaker 1: is coming to town. You want to go see them?
Speaker 1: And I mean like, yeah, totally. So you've got atom
Speaker 1: which consists of that nucleus, and you've got the electron
Speaker 1: cloud around it. When you apply energy, it causes the
Speaker 1: electrons to move to a higher orbit around that nucleus. Again,
Speaker 1: since we're talking about a cloud and not just a
Speaker 1: simple orbit circle, you can think of it as meaning
Speaker 1: the electrons move a little further away from the nucleus.
Speaker 1: If you add enough energy, you can strip electrons away
Speaker 1: from the atom entirely. This will create a charged UH
Speaker 1: atom because you will now have an ion. It's gonna
Speaker 1: have a pause a net positive charge because you're gonna
Speaker 1: have protons there and you've pulled away some of the electrons,
Speaker 1: so you've taken some of that balance out. UH. If
Speaker 1: you add enough electric enough energy, I was about to
Speaker 1: say electro steve a really energy. Electricity is one form
Speaker 1: of energy you could add to the ADAM in order
Speaker 1: to do this. But if you didn't add that much,
Speaker 1: like if you had it enough to excite the electrons
Speaker 1: but not strip them away from the nucleus. When you
Speaker 1: remove that source of energy, the electrons will move back
Speaker 1: down to their ground state. They do not quote unquote
Speaker 1: want to be at that excited level. They have a
Speaker 1: ground state that they are naturally inclined to be at.
Speaker 1: But they've absorbed energy. So in order to move back
Speaker 1: down to their normal energy level, they have to give
Speaker 1: up some of the energy that they've absorbed, and they
Speaker 1: do this through emitting a photon. That basic unit of light,
Speaker 1: and once they emit that photon, that's what allows them
Speaker 1: to move back to their ground energy state because they
Speaker 1: no longer have that excess energy inside of themselves. So
Speaker 1: you can think of it as almost being like the
Speaker 1: elect run is too full, like it's eaten too much,
Speaker 1: and then it has little belchy belch or something it
Speaker 1: manages to emit some part of that energy. It is absorbed,
Speaker 1: and now it's feeling more like its old self again,
Speaker 1: and then you can just boost it back up again
Speaker 1: if you want to. So photons are admitted this way
Speaker 1: through in lasers, but that's not the only way we
Speaker 1: generate photons like there are very specific ways of doing
Speaker 1: this in all sorts of applications, and many of them
Speaker 1: are pretty basic. Like your incandescent lightbulb uses the same principle.
Speaker 1: You run an electric current through some wire a filament,
Speaker 1: typically in a vacuum sealed tube a bulb, and running
Speaker 1: the electric current causes the filament to heat up because
Speaker 1: it has resistance to electrical current, so some of that
Speaker 1: electricity gets converted over into heat. As this heats up,
Speaker 1: it excites the atoms within that filament, and as that
Speaker 1: energy source moves through it allows those electrons to come
Speaker 1: back down the the atoms begin to emit photons, and
Speaker 1: then you get this glow. In the case of light bulbs,
Speaker 1: the glow creates the light you would have from an
Speaker 1: incandescent bulb. You could also see the same thing with
Speaker 1: heating elements, Like if you were to look inside a
Speaker 1: toaster and you see that orange glow, Well, that orange
Speaker 1: glow is coming from the heating elements that have had
Speaker 1: their atoms excited. The electrons got boosted to a higher
Speaker 1: energy level and then they came down and started releasing photons.
Speaker 1: So it's not just lasers that do this, but lasers
Speaker 1: take advantage of it in a very specific way. That's
Speaker 1: pretty cool. Now, that's just what's going on with the
Speaker 1: physics side of things. I haven't yet explained how this
Speaker 1: really works with a laser. So a laser uses this
Speaker 1: principle to create those narrow beams of light. And here's
Speaker 1: how they do it. First, you need what is called
Speaker 1: a lazing medium, a laser medium. This is the stuff
Speaker 1: that you're going to use to excite. You know, you're
Speaker 1: gonna excite the atoms in this stuff so that it
Speaker 1: generates the wavelength of light that you want, and so
Speaker 1: the type of stuff you use that's going to determine
Speaker 1: the type of atoms that are present, which in turn
Speaker 1: determines the energy levels of the electrons, which in turn
Speaker 1: determines what color light you're gonna get through the lasing medium.
Speaker 1: All of this is dependent upon, ultimately the source of
Speaker 1: the lazing medium, Like what is that material? The lasing
Speaker 1: medium acts like an amplifier, only this is for optics
Speaker 1: rather than for acoustics. So some people call the lasing
Speaker 1: medium the gain medium or the source of optical gain
Speaker 1: because it's like a microphone gain setting, it is amplifying
Speaker 1: a signal. Then this case, it's amplifying light, not amplifying sound. Uh.
Speaker 1: The gain in this case is that stimulated mission the
Speaker 1: photons I was talking about, and the emission is stimulated
Speaker 1: through an interesting series of events. You start by initially
Speaker 1: adding energy to the lasing medium, and then the photons
Speaker 1: that emits end up stimulating other atoms inside the lasing
Speaker 1: medium that have already been excited, and then you get
Speaker 1: a steady stream of photons that create your laser beam.
Speaker 1: But first you have to add energy into the system.
Speaker 1: You do this from what is called a pump source
Speaker 1: because you are pumping energy into the lazing medium. So basically,
Speaker 1: you pump energy into this medium, you excite some atoms,
Speaker 1: the those excited atoms start to emit photons. Those photons
Speaker 1: will start to h hit other stimulated atoms and that's
Speaker 1: where you get this um stimulated emission. So there are
Speaker 1: lots of different types of lasing media. So, for example,
Speaker 1: there are certain crystals that can serve as a medium. Uh,
Speaker 1: the earliest lasers were ruby lasers, so you would get
Speaker 1: a ruby crystal and that would be your lasing medium.
Speaker 1: You would usually in introduce some impurities. It's called doping.
Speaker 1: You add some impurities to the material in order to
Speaker 1: make this a more efficient lasing medium. Usually it's some
Speaker 1: ions of some sort um and that helps when you're
Speaker 1: actually getting to the part of generating a laser. Those
Speaker 1: are specifically solid state lasers, the ones that use crystals.
Speaker 1: You're using a solid lasing medium. But there are other
Speaker 1: ones as well. There's some that use glasses, some that
Speaker 1: use gases, including reactive gases like chlorine and florine. Those
Speaker 1: are specific types of gas lasers that are called xemer lasers.
Speaker 1: You have semiconductor lasers, which produce, in the grand scheme
Speaker 1: of things, fairly weak lasers. But they also are fairly
Speaker 1: inexpensive to produce, and those are the ones that we
Speaker 1: use in things like CD players, DVD players, Blu ray players,
Speaker 1: that kind of stuff. They tend to be semiconductor lasers.
Speaker 1: They're easy to mass produce, they're less expensive, and they
Speaker 1: aren't so powerful as to cause problems. You don't need
Speaker 1: a CD player laser that could burn a hole through
Speaker 1: the surface of the Earth. That would be ridiculous. You
Speaker 1: can also get liquid medium lasers. These are liquids that
Speaker 1: have various organic dyes special organic dyes d y e
Speaker 1: s that will allow for this stimulated emission of light
Speaker 1: amplified light. Now, the pump is some sort of energy
Speaker 1: transfer that you use to excite those atoms in the
Speaker 1: first place, so that they'll emit those initial photons when
Speaker 1: the electrons calm the heck down. Laser pumps are some
Speaker 1: form of external source of energy. Typically they supply energy
Speaker 1: in the form of either electricity or light, but there
Speaker 1: are other means of pumping a lazing medium with energy
Speaker 1: to create lasers. Light and electricity are the two most
Speaker 1: common ones, but they are not the only kinds. There's
Speaker 1: some that use chemical reactions. There's some that even use
Speaker 1: nuclear reactions, which I think is taking in a little
Speaker 1: far if you're asking me, uh, that's me mostly being
Speaker 1: tongue in cheek. But again, most of the lasers that
Speaker 1: we would encounter throughout our day, those are generated either
Speaker 1: through light or through electricity stimulating the lasing medium. So,
Speaker 1: for example, most most early lasers were using some form
Speaker 1: of arc or flash lamp to stimulate that initial reaction
Speaker 1: within the atoms of lazing medium, like a crystal rod. Uh. So,
Speaker 1: you got your crystal rod with a few impurities in
Speaker 1: it that you have specifically placed in there. You have
Speaker 1: doped this crystal rod. You would wrap a light source
Speaker 1: around this thing, usually within some sort of mirrored chamber,
Speaker 1: and you would flash light impulses against the lasing medium,
Speaker 1: and this would actually excite atoms within the medium, which
Speaker 1: would then give off photons. Now, if there were no
Speaker 1: way for you to keep this reaction going, it would
Speaker 1: be such a small emission of photons that you probably
Speaker 1: wouldn't even be able to tell. You wouldn't even it
Speaker 1: wouldn't be visible to you. However, by tricking it you
Speaker 1: can totally make it visible. So you typically would use
Speaker 1: these mirrors to reflect light back into the lasing medium.
Speaker 1: That includes photons that were admitted during that initial flash,
Speaker 1: and that's what allows you to create a cascade effect
Speaker 1: and create a laser. Generally speaking, you would probably use
Speaker 1: mirrors that would allow the election of any wavelengths of
Speaker 1: light that were shorter than the laser's wavelength would be,
Speaker 1: and allow the transference of light that is longer, wavelengths
Speaker 1: longer than the laser's wavelength that you want. The reason
Speaker 1: for that is that if you were to trap all
Speaker 1: the light within the chamber, you could cause things to
Speaker 1: heat up and create what's called thermal lensing. The actual
Speaker 1: change in temperature would create a lens effect that would
Speaker 1: end up affecting the ability of a laser to be
Speaker 1: directional and coherent. And obviously, if that's your intent, you
Speaker 1: don't want that to happen. So, yeah, Thermal lensing occurs
Speaker 1: when a sample absorbs energy from a laser beam, it
Speaker 1: heats up, it creates this refractive lens that causes beam divergence.
Speaker 1: That's not what you want with a laser. Typically, I mean,
Speaker 1: you might want to design a system that creates that
Speaker 1: splits a beam, but that's different from beam divergence. You
Speaker 1: want that beam to be nice and tight. Uh, typically
Speaker 1: or your your average laser applications. So let's let's imagine
Speaker 1: that we're building a laser and we start with a
Speaker 1: rod made out of ruby. I was gonna say that
Speaker 1: you could have a ruby rod, but we all know
Speaker 1: that he is busy with Corbin Dallas trying to save
Speaker 1: the universe. Shout out to any of you guys out
Speaker 1: there who understand what that reference means. So you've got
Speaker 1: ruby rod, and you've got a flash tube that is
Speaker 1: probably wrapped around the ruby rod, but at least as
Speaker 1: shining can shine on the ruby rod, and you can
Speaker 1: use the flash tube out of like a camera. In fact,
Speaker 1: the earliest lasers were using camera flashbulbs as the source
Speaker 1: of light to start this reaction. It's not like it's
Speaker 1: something super high tech. It's actually pretty cool. And you've
Speaker 1: got a mirrored chamber that surrounds the whole thing on
Speaker 1: the on either end of the rod. So think of
Speaker 1: the rod is like a cylinder. You have put a
Speaker 1: silvered mirror on either end. One side is a pure
Speaker 1: silvered mirror, so it just reflects light. The other one
Speaker 1: is a partially silvered mirror, meaning that it can allow
Speaker 1: some light to pass through. Specifically, you want to design
Speaker 1: it so it allows the wavelength of the laser light
Speaker 1: to pass through, but doesn't allow any other light to
Speaker 1: pass through. Uh, you turn on the flash tube. This
Speaker 1: shines bright light onto the rod, which causes some of
Speaker 1: the atoms in the rod to excite. Then as those
Speaker 1: electrons move back down from their excited stage back to
Speaker 1: the ground level stage, they release photons, and with enough
Speaker 1: energy pumped into the medium, you end up with a
Speaker 1: larger population of atoms that are in an excited state
Speaker 1: then there are atoms in the ground state. When you
Speaker 1: reach that point, it is called a population inversion because
Speaker 1: you've inverted the relationship between a sited atoms and ground
Speaker 1: state atoms. Typically, you would have more ground state atoms
Speaker 1: than excited ones. Once you're able to flip that balance,
Speaker 1: you can create this cascading effect that I've been talking about.
Speaker 1: So you've got more excited atoms than you have ground
Speaker 1: energy level atoms inside of this lasing medium. At that point,
Speaker 1: they started giving off photons, and this is pretty cool.
Speaker 1: What happens next is photons from some of those first
Speaker 1: UH atoms that had been excited and they were calming down.
Speaker 1: If you like, they'll go out and they'll hit other
Speaker 1: excited atoms. So these are atoms that I've already had
Speaker 1: their energy levels boosted by that flashbulb. The photon from
Speaker 1: the first atom, the one that excited then calmed down,
Speaker 1: has just the right amount of energy to cause the
Speaker 1: electron in an excited atom to come back down to
Speaker 1: its ground state and release a another photon. So what
Speaker 1: happens is the atom that it it connects with will
Speaker 1: absorb the photon, then it will emit the photon and
Speaker 1: emit a second photon as its own electron comes down
Speaker 1: an energy level. So you get two photons emitted, the
Speaker 1: initial one that you shot the atom with and then
Speaker 1: the one that that atom produced itself. So this is
Speaker 1: what it's called light amplification. Right, you have amplified the light.
Speaker 1: You started with one photon. Now you have two photons
Speaker 1: and they're moving in phase with one another because well
Speaker 1: because of quantum physics, but I don't want to get
Speaker 1: into that too much. So you get this light amplification
Speaker 1: through that process. Now that you have the light amplification.
Speaker 1: You might as well say, like, well, what are we
Speaker 1: calling this? This whole process where a photon can cause
Speaker 1: another atom to admit a photon, that's the stimulated emission.
Speaker 1: You might think stimulated emission was when you turned on
Speaker 1: the flash bulb. That's not technically correct. The stimulated emission
Speaker 1: part technically comes from these initial atoms that release photons,
Speaker 1: and those cause this chain reaction in the lasing medium.
Speaker 1: So this can happen over and over and over again. Right,
Speaker 1: You're not really the atoms aren't losing any matter in this.
Speaker 1: It's just a process of electrons being boosted up to
Speaker 1: an energy level and then coming back down again, so
Speaker 1: they're releasing energy. They're not losing anything in this. It's
Speaker 1: just a transfer of energy and really a transformation of
Speaker 1: it from one form of light to another. So it's
Speaker 1: fascinating to me that this is something that not only works,
Speaker 1: but that people were able to figure out would work um.
Speaker 1: It's it's so far into quantum physics and optics and
Speaker 1: photonics that I am amazed that people figured us out.
Speaker 1: In fact, they figured it out way back at the
Speaker 1: beginning of the twentieth century. It would take the middle
Speaker 1: of the twentieth century before anyone built a working laser,
Speaker 1: but they figured out the physics of it decades ahead
Speaker 1: of time, and that still blows my mind to this day.
Speaker 1: Then again, I'm also the guy who can't figure out
Speaker 1: which remote control controls the TV versus the audio system.
Speaker 1: So what do I know. You get this series of
Speaker 1: photons being omitted that are all in phase with one another,
Speaker 1: and they bounce back and forth between these two mirrored
Speaker 1: ends of this ruby rod. But some of them can
Speaker 1: pass through the half silvered or partially silvered end because
Speaker 1: that it allows for that, and this is the source
Speaker 1: of the laser beam. The photons that get out through
Speaker 1: that end become the laser beam, and it's just a
Speaker 1: steady beam of light that will continue to fire as
Speaker 1: long as this reaction is allowed to continue. If you
Speaker 1: remove that source of energy, the pump energy that is
Speaker 1: allowing this to happen in the first place, it will stop,
Speaker 1: right it will. The reaction is not sustaining. It can't
Speaker 1: just keep on going, and you have to have that
Speaker 1: external source of energy to maintain it throughout the whole process,
Speaker 1: otherwise it just goes dark. So that's basically how your
Speaker 1: standard laser works. Now, if you're using that ruby based
Speaker 1: laser I was talking about, the wavelength of the laser
Speaker 1: light could be measured at six hundred and ninety four nanometers.
Speaker 1: That's how long a wavelength of ruby laser is. Six
Speaker 1: which is incredibly tiny. The visible spectrum of light is
Speaker 1: between four nimes, which would be the violet side, up
Speaker 1: to seven nimes, which is the red side. So this
Speaker 1: ruby one is right up there at the top level
Speaker 1: of what we can see as human beings. Now, you
Speaker 1: can also have infrared or ultra violet lasers. Obviously those
Speaker 1: would be invisible to us, but they would still exist
Speaker 1: and you can still do some pretty cool stuff with it.
Speaker 1: In fact, uh, infrared lasers are often used to cut
Speaker 1: steel for example. Much pretty serious stuff when you think
Speaker 1: about it. But we'll talk about that more in a
Speaker 1: little bit Before we get into more about Pepe lasers.
Speaker 1: Let's take a quick break to thank our sponsor. Now.
Speaker 1: According to the company Wicked Lasers, which makes a range
Speaker 1: of laser products, including ones that are capable of actually
Speaker 1: burning stuff if you use them, uh, they say that
Speaker 1: the wavelength of five five nanometers is ideal for brightness
Speaker 1: compared to other colors that are produced at that same
Speaker 1: amount of power. So lasers have a couple of different
Speaker 1: elements to them. There's the wavelength of the laser itself,
Speaker 1: and then there's the amount of power that you are
Speaker 1: able to generate. You measure laser power in in milliwatts
Speaker 1: typically for the ones that we use uh day to
Speaker 1: day as consumers. They can go higher than milliwatts, but
Speaker 1: typically the ones we consumers use are in the milliwatt
Speaker 1: lage range rather uh. But you you would measure them
Speaker 1: in watts the same way you would with light bulbs.
Speaker 1: But a ten what laser or a fifty watt laser
Speaker 1: would be much more much brighter than a fifty watt
Speaker 1: light bulb, because remember a fifty what light bulb is
Speaker 1: giving out fifty watts of light, but it's it's emitting
Speaker 1: that in practically all directions, whereas a laser has it
Speaker 1: very much concentrated in a coherent beam. So a fifty
Speaker 1: laser would be incredibly bright compared to a fifty watt
Speaker 1: light bulb. We're mostly talking about milliwatts. So if you
Speaker 1: have a a certain laser pointer of let's say let's
Speaker 1: just say twenty milliwatts. I mean, it's incredibly small, but
Speaker 1: this is just for the purposes of an example, twenty
Speaker 1: milliwatt laser pointer, and it's green, which is closer to
Speaker 1: that five fifty five nanometers in wavelength, and then you've
Speaker 1: got another one that's read. The green one's gonna appear
Speaker 1: brighter than the red one, even if they're both emitting
Speaker 1: the same wattage of laser light, because our visual acuity
Speaker 1: is closer to that five fifty five nanometer wavelength range.
Speaker 1: So violet and blue lasers are slightly less powerful than that,
Speaker 1: but the greens are the ones that are going to
Speaker 1: show up the best for their respective amount of power. Obviously,
Speaker 1: you can pour more power into a laser, and in
Speaker 1: some cases you can end up with a brighter laser
Speaker 1: because of it, of course, depending upon whether or not
Speaker 1: the laser is within the visible spectrum in the first place.
Speaker 1: It doesn't matter how much power you pour into an
Speaker 1: infrared laser. You're never gonna see it. You'll see the
Speaker 1: results because it will burn through stuff, but you won't
Speaker 1: see the laser itself. But yeah, it's all it's all
Speaker 1: about those extra things as well, not just the wavelength,
Speaker 1: but also the power. So that's really what helps determinal
Speaker 1: laser strength is the wavelength and the amount of power
Speaker 1: that it's putting out. Really, how much power are you
Speaker 1: putting in and getting out of it? So if I
Speaker 1: want to use a death laser in order to defeat
Speaker 1: my arch nemesis who happens to be a British secret spy,
Speaker 1: and I want to also use another laser to amuse
Speaker 1: my cat but not turn it into kitty cat flambay,
Speaker 1: what do I need to do to make sure about that? Well,
Speaker 1: one is again that wavelength of light. Certain wavelengths are
Speaker 1: absorbed more readily by a broader variety of substances than
Speaker 1: other wavelengths. So if you pick a wavelength that is
Speaker 1: easily absorbed by lots of different stuff, that is going
Speaker 1: to transfer energy more readily to your target. So, as
Speaker 1: it turns out, and for red lasers can really transfer
Speaker 1: a lot of energy to a broad array of stuff,
Speaker 1: including steel. That's why carbon dioxide megawatt lasers are used
Speaker 1: to cut through stuff like sheets of steel. But other
Speaker 1: colors are not as easily absorbed by as wide a
Speaker 1: variety of materials, and so you would really have to
Speaker 1: pour more energy into the laser in order to get
Speaker 1: a beam strong enough to start cutting through stuff. So
Speaker 1: it depends on both how much power you're putting into
Speaker 1: the laser and the wavelength of the light. Both of
Speaker 1: those together will determine how strong quote unquote your laser is.
Speaker 1: Strong isn't really a meaningful term because there are different
Speaker 1: ways of measuring laser. It's by how much light it
Speaker 1: gives off and also how much energy does it transfer
Speaker 1: to a target. But if you're talking about the energy
Speaker 1: transferred to a target, those are the two things you
Speaker 1: have to worry about. The wavelength and the amount of
Speaker 1: power that it generates. You can use other stuff to
Speaker 1: help with that too, like lenses. You can use lenses
Speaker 1: to help maintain a tighter laser for further distances, but
Speaker 1: ultimately it's power and wavelength that you're really concerned with. AH.
Speaker 1: Lasers can be used for all sorts of things, from
Speaker 1: optical media like DVDs, blue rays, and CD players, to
Speaker 1: communication systems to massive industrial lasers UH that can cut
Speaker 1: through steel like warm butter and they're really nifty. But
Speaker 1: I thought it might be interesting to learn a little
Speaker 1: bit more about not just how lasers work, but sort
Speaker 1: of the the history of lasers as well, right, because
Speaker 1: there's a ton of different stuff to to talk about.
Speaker 1: I mean, who figured out how lasers would even be
Speaker 1: a thing? Like where did that come from? So to
Speaker 1: trace the history of the laser, you have to look
Speaker 1: at the scientists whose work provided the foundation for all
Speaker 1: the people who followed. So all the scientists and engineers
Speaker 1: who actually started building lasers in the nineteen fifties, they
Speaker 1: did this working off of the theoretical work of people
Speaker 1: who came before them. So one of those people was
Speaker 1: Max Planck. So Planck was born in eighteen fifty eight
Speaker 1: in Germany, and his father was a law professor. And
Speaker 1: when he was a kid, he was really good at
Speaker 1: study aims stuff. He was really interested in tons of
Speaker 1: different things. He was he was a bit of a pollymath,
Speaker 1: really intelligent and very and very accomplished in several fields,
Speaker 1: uh including music. And in fact, when he turned seventeen,
Speaker 1: he had to make the tough decision what was he
Speaker 1: going to pursue as a care ere Was he going
Speaker 1: to continue to study science or was he going to
Speaker 1: become a musician. And somewhere there's an alternate universe where
Speaker 1: Plank decided to become a musician instead of a physicist,
Speaker 1: and in that alternate universe we had totally different types
Speaker 1: of piano music that Plank would have written. It would
Speaker 1: have been amazing. But I think we're pretty thankful for
Speaker 1: his contributions to science. So ultimately, if we were to
Speaker 1: measure us versus them, I think we get the better
Speaker 1: end of the deal. But still, it's really interesting to
Speaker 1: think that he could have become a musician instead of
Speaker 1: a physicist. And he's sort of the father of quantum physics,
Speaker 1: so if he had not gone into study physics, it
Speaker 1: might have delayed our study of quantum physics as a
Speaker 1: discipline by at least a decade, potentially more because his
Speaker 1: work would go on to inspire lots of other heavy thinkers,
Speaker 1: including Mr Albert Einstein. So Plank earned his doctorate the
Speaker 1: same year as Einstein's birth, so Planka's predecessor to Albert Einstein, obviously,
Speaker 1: and Einstein would take inspiration from several of plans ideas,
Speaker 1: and one of those was plucks idea that energy could
Speaker 1: only be emitted and absorbed in discrete amounts. So if
Speaker 1: you think about it, it's almost more like digital versus analog.
Speaker 1: If you've listened to me talk about digital audio, you
Speaker 1: know how digital audio is made up of tiny little
Speaker 1: steps of pitch and volume, whereas analog is a continuous wave. Right,
Speaker 1: digital audio is a bunch of discrete little moments in time,
Speaker 1: and the number of those moments in time that's your
Speaker 1: sample rate. The more the higher your sample rate is,
Speaker 1: the closer this looks to be a continuous line. But
Speaker 1: it's not really a continuous line. It's tiny little steps
Speaker 1: in pitch and volume. Well, Planck's point was that energy
Speaker 1: is sort of similar it. Ultimately, when you get down
Speaker 1: to the very very very tiny amounts could only be
Speaker 1: omitted or absorbed in discrete chunks. It's not continuous, not analog,
Speaker 1: And this was a revolutionary idea. Einstein would end up
Speaker 1: looking at this idea and saying this is pretty cool. Um,
Speaker 1: I'm gonna use this and add on to it, and
Speaker 1: he created his theory about the photo electric effect. Plank, meanwhile,
Speaker 1: would end up being awarded the Nobel Prize in Physics
Speaker 1: in nineteen eighteen for his his working quantum mechanics. Einstein
Speaker 1: would similarly be honored several times. It was Einstein who
Speaker 1: first suggested that Adams might be able to produce photons
Speaker 1: through stimulated emission. So lasers are somewhat built upon the
Speaker 1: theories of Einstein himself. He stated that electrons could be
Speaker 1: stimulated to a mid light of a specific wavelength, which
Speaker 1: of course is the very basis of lasers. And Einstein
Speaker 1: published that theory in nineteen seventeen, so it would be
Speaker 1: nearly forty years before anyone could actually build something to
Speaker 1: test out and see if Einstein's theory was of practical application. Uh,
Speaker 1: but it turns out he was right, which again blows
Speaker 1: my mind. Forty years before anyone could build something, and
Speaker 1: he's saying, hey, you know what probably would work. Ah,
Speaker 1: I'm oversimplifying it and making light of it. But I
Speaker 1: am in awe of people who are able to think
Speaker 1: in these terms, where they're able to work out the
Speaker 1: basic laws of the universe well before we could ever
Speaker 1: make any sort of practical attempt to test those ideas.
Speaker 1: It is phenomenal to me. Now. Granted, I could make
Speaker 1: up laws of the universe, but they would be completely
Speaker 1: unsubstantiated and would face old to hold up to any
Speaker 1: testing in the future. I lack the ability to have
Speaker 1: that level of insight into how our universe works. But
Speaker 1: I do appreciate it in others. So let's flash forward
Speaker 1: the nineteen fifty one. So we go from nineteen seventeen
Speaker 1: to nineteen fifty one. That's when a guy named Charles H. Towns,
Speaker 1: who worked at Columbia University in New York, was sitting
Speaker 1: on a park bench, which in itself is not that remarkable,
Speaker 1: but he came up with an idea of creating a
Speaker 1: device that could produce microwaves through stimulated emission of radiation,
Speaker 1: and this idea became the basis of the Mazer m
Speaker 1: a s E er, which is similar to the laser,
Speaker 1: but obviously amidst microwaves rather than light. Three years later,
Speaker 1: Towns would demonstrate a working maser. So this is nineteen
Speaker 1: fifty four, not a laser, yet still a mazer. So
Speaker 1: microwaves are part of the electromagnetic spectrum, but are not
Speaker 1: considered of light. Right, you've gone beyond infrared at this point.
Speaker 1: The wavelengths of microwaves are much much, much longer than
Speaker 1: the wavelengths of light. Towns had actually partnered with a
Speaker 1: couple of people in order to create this working maser
Speaker 1: that included Herbert J. Zeiger and a graduate student named
Speaker 1: James P. Gordon. They used ammonia as their medium for
Speaker 1: the mazer, and the wavelength of the microwave was one centimeter.
Speaker 1: A centimeter is it's it's almost impossible for me to
Speaker 1: describe how big that is compared to the the waves
Speaker 1: that are in the nanometer range, the hundreds of nanometers,
Speaker 1: but it is while centimeter is small to us, it
Speaker 1: is enormous in the quantum world. So they were able
Speaker 1: to create this. They were able to build a working
Speaker 1: maser using ammonia as their medium. Now in Moscow around
Speaker 1: the same time, there are a couple of engineers, Nikolai G.
Speaker 1: Basov and Alexander M. Prokhorov, who were working on building
Speaker 1: oscillators at the time, and while they were building oscillators,
Speaker 1: they came up with a method that they thought would
Speaker 1: work for negative absorption while building these things, and they
Speaker 1: called it the pumping method, which would become important for
Speaker 1: future mazers and lasers. In nineteen fifty six, Nicholas Blomberg
Speaker 1: in at Harvard develops the first solid state mazer. In
Speaker 1: September nineteen fifty seven, Towns would sketch out an optical
Speaker 1: mazer design in a lab notebook. Also in nineteen fifty seven,
Speaker 1: there was a guy named Gordon Gould who was a
Speaker 1: grad student at Columbia who wrote down his own ideas
Speaker 1: for a device that would be similar to a mazer,
Speaker 1: but he called this one a laser. So this appears
Speaker 1: to be the first use of the word lasers, the
Speaker 1: first recorded instance of laser as a word. And Gould
Speaker 1: thought ahead and even had his notes notarized. So he
Speaker 1: had them notarized by a notary, well as a date
Speaker 1: on it and everything, so that he could prove that
Speaker 1: he had come up with this notion. He tracked down
Speaker 1: a notary at a candy shop and the bronx, which
Speaker 1: is a phenomenal story in my mind. I love the
Speaker 1: idea that this is non joke. This really happened. You
Speaker 1: had a guy come up with what would become a
Speaker 1: transformative technology, a laser, like the idea of creating a
Speaker 1: light version of what had already happened, And so he
Speaker 1: needs it notarized, so he goes to a candy store.
Speaker 1: It's pretty sweet when you think about it. By nineteen
Speaker 1: fifty eight, Towns was working with his brother in law,
Speaker 1: Arthur L. Shallow or Shallow, I guess is the way
Speaker 1: you would pronounce it sc h A W l O
Speaker 1: W Shallow. He was a researcher for Bell Labs, which
Speaker 1: obviously has played an enormously important role in the development
Speaker 1: of electronics in general. Together they proposed developing masers that
Speaker 1: could operate in the infrared and optical parts of the
Speaker 1: electromagnetic spectrum. And meanwhile, over in Russia, Prokhorov and Basov
Speaker 1: were also investigating the possibility of developing optical mazers. So
Speaker 1: the race was on a lot of different people all
Speaker 1: trying to create an optical mazer or laser. In April
Speaker 1: nineteen fifty nine, Gould would apply for patents relating to lasers,
Speaker 1: and in nineteen sixty Townsend Shallow received a patent for
Speaker 1: the optical mazer, which they now were calling a laser,
Speaker 1: and thus the Great Laser Battle began. Only this laser
Speaker 1: battle wasn't fought with lasers. It was fought over the
Speaker 1: intellectual property represented by lasers. And this was a legal
Speaker 1: battle that would stretch for three decades. So an incredible
Speaker 1: laser battle really. But the first working laser was built
Speaker 1: in Malibu, California, in nineteen sixty and almost certain he
Speaker 1: had nothing to do with plastic surgery, unlike everything else.
Speaker 1: In Malibu, California, Theodore H. Maiman, who worked at Hughes
Speaker 1: Research Labs in Malibu, built this first laser. He used
Speaker 1: a synthetic ruby that was two centimeters long and one
Speaker 1: centimeter in diameter, and he coated the ends in silver
Speaker 1: to make them reflective. He used a photographic flash lamp
Speaker 1: to pump the lasing materials, so he used the exact
Speaker 1: same sort of flash bulbs you would find in a
Speaker 1: cameras flash, which is pretty incredible. And a couple of
Speaker 1: months later, Hughes Research would hold a press conference to
Speaker 1: announce that they had developed the first working laser. A
Speaker 1: few months after that, scientists at IBMS Thomas J. Watson
Speaker 1: Research Center demonstrated a working uranium laser, which seems like
Speaker 1: a massive show of escalation in my mind. Now, at
Speaker 1: this point the developments would come really fast and furious,
Speaker 1: not like the film series within Diesel, but I mean
Speaker 1: they were just laser development after laser development, tons of advances.
Speaker 1: I'm not going to cover all of them because they're
Speaker 1: way too many, but I'll cover some of the big ones.
Speaker 1: The first helium neon laser debut at the end of
Speaker 1: nineteen sixty, again at Bell Labs, and it was able
Speaker 1: to create a one point one five micrometer wavelength of
Speaker 1: continuous light, so beyond the range of human vision. It
Speaker 1: wasn't light that was visible, but it was in the
Speaker 1: spectrum of light. And in nineteen sixty one companies began
Speaker 1: to manufacture lasers for the market. This is incredible to me.
Speaker 1: It what had been only a year since someone had
Speaker 1: built a working laser, and by the following year people
Speaker 1: were making them for for sale. Now, granted, they weren't
Speaker 1: selling them to average consumers. It's not like John Smith
Speaker 1: or or or John Q. Public if you prefer it,
Speaker 1: could walk into the closest laser store in order a laser.
Speaker 1: These were meant for research and development purposes and not
Speaker 1: for people who wanted to amuse their cat. It was
Speaker 1: also meant for some early industrial uses and as it
Speaker 1: turns out, some early medical uses. So again I'm gonna
Speaker 1: jump over some of the incremental developments. It wouldn't make
Speaker 1: sense for me to cover all of them, and a
Speaker 1: lot of them I would have to go into even
Speaker 1: more description about very specific types of lasers which only
Speaker 1: apply to particular cases and not to others, and that
Speaker 1: would just make this kind of muddy and and and directionless.
Speaker 1: But I do want to point out a few really
Speaker 1: cool moments in history and explain some related topics to
Speaker 1: lasers as a result, such as what happened in December
Speaker 1: of nineteen sixty one. So keep in mind it only
Speaker 1: been a bit longer than a year since someone had
Speaker 1: demonstrated a working laser at all. But in December nineteen
Speaker 1: sixty one, Dr Charles J. Campbell and Charles J. Custer,
Speaker 1: I'll have Charles Jay's decided that they were going to
Speaker 1: treat a patient, a medical patient, a human medical patient,
Speaker 1: using an optical be laser to destroy a retinal tumor.
Speaker 1: Now that's incredible. It had been only eighteen months since
Speaker 1: someone had built the first working laser, and you already
Speaker 1: had people using it in a medical procedure on a
Speaker 1: human patient. I suspect that today it would take a
Speaker 1: bit longer to prove that the methodology being used was
Speaker 1: safe and efficacious before using it on a human, but
Speaker 1: it shows how quickly things were moving back then. I
Speaker 1: think it's pretty incredible that it took less than two
Speaker 1: years to actually use lasers in a medical and an
Speaker 1: actual medical procedure. Now, the mid nineteen sixties would see
Speaker 1: advances in the field of fiber optics, which, when paired
Speaker 1: with lasers, allow for long distance communication using light through
Speaker 1: glass filaments. Now, I've done episodes about fiber optics before,
Speaker 1: so you can go and look at the Tech Stuff
Speaker 1: archives and learn more about that. But this still blows
Speaker 1: my mind too. Just the fact that fiber optics are
Speaker 1: a thing that work, it is incredible to me. Meanwhile,
Speaker 1: Bell Labs would strike again in nineteen seventy two with
Speaker 1: a laser beam cutter they used to form electronic circuit
Speaker 1: patterns on ceramic and on June nineteen seventy four, which
Speaker 1: just for Trivia's sake, is exactly one year to the
Speaker 1: day before I was born. A barcode scanner, which typically
Speaker 1: uses lasers. Read the very first product ever registered for
Speaker 1: real z s using a UPC code and a barcode scanner.
Speaker 1: The product, by the way, it was a pack of
Speaker 1: Wriggley's chewing gum. So how the heck did those barcode
Speaker 1: scanners work? Because you see him on everything these days
Speaker 1: and here's where I'm gonna go on a bit of
Speaker 1: a tangent to talk about bar codes in just a second.
Speaker 1: And I also just want to mention that, uh, I
Speaker 1: think it's really cool that, now you know a trivia
Speaker 1: question that the first product to ever be scanned using
Speaker 1: a barcode scanner was Wriggley's chewing gum. Important to remember
Speaker 1: in case you ever played bar trivia. Now, next, I'm
Speaker 1: gonna talk all about you PC codes and how they work.
Speaker 1: But before I jump into that and go way off
Speaker 1: the rails, let's take another quick break to fake our sponsor.
Speaker 1: All right, So let's talk about bar codes, which are
Speaker 1: I agree, tangentially related to lasers. But I've already talked
Speaker 1: about how lasers work, and I really love how bar
Speaker 1: codes work because I just think they're kind of cool.
Speaker 1: So these are the good old universal product code or
Speaker 1: UPC code things that you would see on products today
Speaker 1: at your average store. Uh. They were designed in order
Speaker 1: to help speed up check out and also make it
Speaker 1: easier to keep a working inventory of a store. And
Speaker 1: you can just scan each item and then you use
Speaker 1: a computer database to match the scan with other information
Speaker 1: like what that product is, how much it costs. So
Speaker 1: the scanner all it needs to do is ident a
Speaker 1: fi which product you are actually scanning at any given time.
Speaker 1: That's its only job. It doesn't really have anything to
Speaker 1: do with how much something costs. That is not necessarily
Speaker 1: represented in the code itself. There are codes that do
Speaker 1: have the information in them, but the basic UPC code
Speaker 1: is really just to tell a system what the product is,
Speaker 1: and then you have a separate database that links products
Speaker 1: to prices. So what would you do if you were
Speaker 1: a manufacturer and you wanted to put a UPC code
Speaker 1: on something that you yourself were making, your company was making.
Speaker 1: Here's the process. You have a company called the Uniform
Speaker 1: Code Council or you see C, and they are in
Speaker 1: charge of UPC codes. And to me, the u c
Speaker 1: C sounds like it should be staffed by shadowy figures
Speaker 1: in robes. But to be fair, I did watch Hot
Speaker 1: Fuzz again not too long ago, and that's probably why
Speaker 1: I'm thinking that. So let's say you're a manufacturing company
Speaker 1: and you make a very specific product and you want
Speaker 1: to get it into stores around the world. And since
Speaker 1: the earliest implementations of the UPC codes were for grocery stores,
Speaker 1: Let's say that it's a grocery store products. So let's
Speaker 1: say you're making a really awesome, tasty, sugary breakfast cereal
Speaker 1: for kids, and you're calling them Crispy Doos. So you
Speaker 1: make delicious Crispy doos that are a nutritional part of
Speaker 1: a balanced breakfast. You want to sell Crispy doos and
Speaker 1: grocery stores, so you want to end up selling to
Speaker 1: grocery stores. Grocery stores will sell the Crispy dues too
Speaker 1: to their their customers and everyone benefits, presumably assuming that
Speaker 1: there's enough nutritional value in the Crispy dues to not,
Speaker 1: you know, turn your customers into goo. So grocery stores
Speaker 1: love the idea of UPC codes because again, it makes
Speaker 1: it much easier to ring up products and it makes
Speaker 1: it very easy to keep track of the stock that
Speaker 1: the grocery store has. If they notice that they're selling,
Speaker 1: you know, eight palettes of Crispy Doos a week, then
Speaker 1: they might up their order and that's good for you.
Speaker 1: So it benefits you to get a UBC code on
Speaker 1: your product. To do that, you would first have to
Speaker 1: apply for a manufacturer identification number from the u c C.
Speaker 1: This is almost like a subscription service. You'd have to
Speaker 1: pay the u c C to get this manufacturer identification number. Uh,
Speaker 1: the u c C would then issue you this number.
Speaker 1: It's a six digit number. And if you look at
Speaker 1: a UPC code, you'll see that there are twelve digits
Speaker 1: on the UPC code. So those are the human readable digits, right,
Speaker 1: that's the thing that you have to type in, and
Speaker 1: for some reason the scanner is not scanning anything you
Speaker 1: might type in the code. Well, those first six digits
Speaker 1: refer to the manufacturer identification number, So all the products
Speaker 1: from that specific manufact acturer should have those first six
Speaker 1: numbers the same on all of them because it's it's
Speaker 1: unique to the company itself. It doesn't matter what the
Speaker 1: product is. The next five digits on that UPC code
Speaker 1: represent the item number, so it's unique to the product.
Speaker 1: So if you make fourteen different products, each product is
Speaker 1: going to have its same or its own five digit
Speaker 1: item code, and it will be different from the other
Speaker 1: thirteen item codes. So if your company also produced, say
Speaker 1: Flea colors for kitty cats, the five digits for the
Speaker 1: fleet colors are going to be different than the five
Speaker 1: digits for the Crispy Dues. Which is good because you
Speaker 1: don't want to mix up your Flea colors with your
Speaker 1: Crispy Dues. That would be a pr nightmare, and this
Speaker 1: episode really isn't meant to go into that sort of thing.
Speaker 1: So that leaves one digit left over. Right, You've got
Speaker 1: the first six that's the manufacturer I D number, the
Speaker 1: next five which is the item number. But you have
Speaker 1: a single digit leftover of those twelve, so is that
Speaker 1: for That is called the check digit, and the check
Speaker 1: digit is meant to give the scanner the opportunity to
Speaker 1: verify that it has scanned the product properly. And the
Speaker 1: way you do this is through some pretty ridiculous math.
Speaker 1: It's not difficult, it's just tedious. So it's again a
Speaker 1: verification right to say that, yes, the scan went through properly,
Speaker 1: because if the math checks out, if you get the
Speaker 1: answer you're supposed to get, you know that you scanned
Speaker 1: it properly. And by you, I mean the scanner system
Speaker 1: is able to verify that a scan went through correctly.
Speaker 1: So let's take a second to talk about how you
Speaker 1: arrive at the check digit so you can understand what
Speaker 1: I mean when you do some ridiculous arithmetic it's not
Speaker 1: difficult again, it's just ridiculous. So you've got eleven other
Speaker 1: digits in the UPC code, and those are what you
Speaker 1: use to do the arithmetic. First, you take all the numbers,
Speaker 1: all the digits and the UPC codes that are at
Speaker 1: odd positions, so not the odd numbers, just in the
Speaker 1: odd positions. So that would be the position number one,
Speaker 1: position number three, five, et cetera, up to eleven. Because
Speaker 1: you have eleven other numbers, you take all of those
Speaker 1: and you add them together and you get a sum.
Speaker 1: So you've got that sum by adding all the odd
Speaker 1: position numbers together, and you then multiply that by three.
Speaker 1: Now you look at all the digits that are in
Speaker 1: even positions, so two, four, six, eight, and ten, you
Speaker 1: add all of those together. You then take the number
Speaker 1: you got from all the odd positions multiplied by three,
Speaker 1: and all the even positions added together, and you add
Speaker 1: those two numbers to other, and then you take a
Speaker 1: look at this new number, this monstrosity of a thing.
Speaker 1: It's not a huge number, it's just weird that you've
Speaker 1: got it. And you say, all right, how many more
Speaker 1: numbers would I have to add to this in order
Speaker 1: to get a multiple of ten, and as long as
Speaker 1: the last digit is the same as the number you
Speaker 1: need to add to your your monstrosity to get a
Speaker 1: multiple of ten, you're good to go. So this is
Speaker 1: easier to understand with an example. So here's our UPC code.
Speaker 1: We've got our crispy doos, and our UPC code happens
Speaker 1: to be six three nine three eight two zero zero
Speaker 1: zero three nine three. Well, that last three is the
Speaker 1: check digit. That's the number we're supposed to get at
Speaker 1: the end of all this other nonsense. So we put
Speaker 1: that aside. We say three is what we're hoping is
Speaker 1: the outcome. How do we get to that. We take
Speaker 1: all those odd positioned digits, which would be six and
Speaker 1: nine and eight, etcetera, etcetera. We add them all up.
Speaker 1: Technically it's six to zeros and nine. That gets you
Speaker 1: thirty two. You multiply that number by three, you get
Speaker 1: ninety six. So that's your that's your first number. You
Speaker 1: set that aside. Your ninety six is good to go.
Speaker 1: Then you take a look at all the even positioned
Speaker 1: numbers and you add those up. The even position numbers
Speaker 1: would be a three, A three, two, zero, and another three.
Speaker 1: That gives you eleven. So now you add the eleven
Speaker 1: to the ninety six that you arrived at earlier. That
Speaker 1: gives you a hundred and seven. You look at a
Speaker 1: hundred and seven and say, how many digits or how
Speaker 1: much when I need to add to this to make
Speaker 1: a multiple of ten? Answers three, because if you had
Speaker 1: three seven you get a hundred and ten hundred ts
Speaker 1: multiple of ten. There you go. Three is the number
Speaker 1: you wanted. Three is the number that's the check digit.
Speaker 1: You know that you've got the right answer. Now. The
Speaker 1: way the scanner does this is not by looking at
Speaker 1: the digits. It's looking at the relationship between the thin
Speaker 1: uh bars, the gaps between the bars, and how thick
Speaker 1: or thin each of those are. Right. So, if you
Speaker 1: look at a UPC bar code, you're looking at just
Speaker 1: the bars. You'll see some of the bars are thin,
Speaker 1: some of the bars are a little thicker, some of
Speaker 1: the gaps between the bars are thinner or thicker than
Speaker 1: the others. That relationship of bars to gaps and the
Speaker 1: thickness of them tells you what the value is of
Speaker 1: each of those. And if you're really really wanted to,
Speaker 1: you could decode to bar code just by sight once
Speaker 1: you know the basic system of coding, and if you're
Speaker 1: able to determine what is a narrow versus a wide
Speaker 1: bar or gap, because that's very important. So the scanner
Speaker 1: is looking at the series of bars and gaps and
Speaker 1: measuring those those widths, and by measuring it, it then
Speaker 1: is able to match that to a numeric code and
Speaker 1: verify whether or not it matches that check digit at
Speaker 1: the end, and if it does, the scan goes through,
Speaker 1: it gets matched to a product and you're charged however
Speaker 1: much or your crispy dewes. I'm gonna say it's five
Speaker 1: for a BUX, so that's what would pop up. There
Speaker 1: are variations on these UPC codes like zero suppressed number
Speaker 1: UPC codes, which is exactly what sounds like. Any number
Speaker 1: that is a zero that would otherwise appear in the
Speaker 1: code gets emitted omitted rather not emitted, it's omitted from
Speaker 1: the code, so it's shorter, makes a shorter barcode. Uh,
Speaker 1: But not everyone does this. Only some products have this
Speaker 1: AH and the manufacturing I D numbers can have a
Speaker 1: specific meaning as well, depending on what number they start with.
Speaker 1: So if you're manufacturing I D number starts with a two,
Speaker 1: it means that it is a random weight prod ducked.
Speaker 1: And by random weight we mean it's something that doesn't
Speaker 1: come in a specific uniform size and weight over and
Speaker 1: over again. So produce. For example, an apple is gonna
Speaker 1: be its own weight, right, You're not going to get
Speaker 1: two apples of the exact same weight. They're not all uniform.
Speaker 1: Whereas if I go out and buy a box of
Speaker 1: Crispy DU's, it should be more or less the same
Speaker 1: as a comparable Crispy Due box. Now if you have
Speaker 1: if you have different sizes of boxes, then you have
Speaker 1: different item numbers for each of those different sizes. The
Speaker 1: item numbers are specific to a very particular instance of
Speaker 1: an item. So if I've got a large box of
Speaker 1: Crispy Us and a small box of Crispy Dues, each
Speaker 1: of those will have its own five digit item number,
Speaker 1: and thus the bars that correspond with it will be
Speaker 1: slightly different as well. Um, by the way, if you
Speaker 1: wanted to know, like, just as an example, what these
Speaker 1: bars mean, I'm not gonna go through the encoding of
Speaker 1: every single number because it would be kind of silly.
Speaker 1: But let me give you an example. If you want
Speaker 1: to represent the number one in a UPC code. The
Speaker 1: way it would work is that you would use uh first,
Speaker 1: a black bar that is two units wide, so in
Speaker 1: other words, you have to look at the most narrow
Speaker 1: bar on the UPC code that's probably one unit right.
Speaker 1: You would want a bar that's twice that. With the
Speaker 1: bar units go up from one to four, so the
Speaker 1: widest bar will probably be four units wide, the thinness
Speaker 1: will probably one unit wide. You need one that's two
Speaker 1: units wide, followed by a space that is two units wide,
Speaker 1: followed by another black bar that's two units wide, followed
Speaker 1: by a space that is one unit wide. So that
Speaker 1: is the number one in bar code speak, and each
Speaker 1: of the new roles is encoded in a similar way.
Speaker 1: Using these bars and gaps of varying widths and reading
Speaker 1: them by sight is possible but is not practical. But
Speaker 1: when you move one of those bars across the scanner,
Speaker 1: the scanner shoots light, typically red laser light, at the
Speaker 1: bar code, and then a sensor on the scanner is
Speaker 1: looking for reflected light and it can detect those bars
Speaker 1: and gaps based upon the light that gets reflected back
Speaker 1: at the sensor and as long again as that last
Speaker 1: bar or that last digit matches up with the math
Speaker 1: I talked about earlier. It can then ring up the
Speaker 1: product and give you the appropriate price for it. Uh So, really,
Speaker 1: the the interesting thing here is that the laser just
Speaker 1: makes this incredibly efficient. I mean, light travels faster than
Speaker 1: anything else in the world, so it's no surprise that
Speaker 1: you can just swing one of these barcodes by it
Speaker 1: a really good clip and still get a really solid
Speaker 1: scan off of it, because that information is going to
Speaker 1: the code and back to the scanner at the speed
Speaker 1: of light, so it's not like you're gonna be moving
Speaker 1: that fast compared to the scanner um and as long
Speaker 1: as it's got that good fidelity there, then you're gonna
Speaker 1: get a pretty successful scan. That's why you can zoom
Speaker 1: stuff past that scanner pretty quickly. Now, let's go back
Speaker 1: to that timeline that we were talking about earlier. By
Speaker 1: Laser Diode Labs Incorporated had developed a continuous wave semiconductor
Speaker 1: laser which would make it possible to transmit telephone conversations
Speaker 1: via optic fiber, which again blows my mind that you
Speaker 1: could turn something that's acoustic not just into electricity, which
Speaker 1: is already magic in my mind, but into light signals.
Speaker 1: In we got the laser disc, which was the first
Speaker 1: commercial use of an optical medium, that being something that
Speaker 1: could be stored on a device that would be read
Speaker 1: just by laser light alone. Laser discs were a predecessor
Speaker 1: to other optical based media like compact discs, a K
Speaker 1: C d s and DVDs and blu rays. The earliest
Speaker 1: players actually used helium neon laser tubes in order to
Speaker 1: read the information stored on the discs, but later ones
Speaker 1: would switch to more affordable infrared laser diodes, so semiconductor
Speaker 1: based lasers. And as I said earlier, the semiconductor approach
Speaker 1: was less powerful and less expensive than other methods of
Speaker 1: generating lasers, so that helped bring the laser disc price
Speaker 1: down a little bit, but they were pretty expensive and
Speaker 1: never really took off. I mean, there were people who
Speaker 1: loved laser discs, but um they never became as popular
Speaker 1: as vhs or later on DVD players. Now later in night,
Speaker 1: Philips would announce it was working on the compact disc project,
Speaker 1: which is kind of funny because I always think of
Speaker 1: CDs as being either a late eighties or early nineties phenomenon,
Speaker 1: But it's origins date back to the late seventies, and
Speaker 1: the first actual CD produced would come out in nineteen two.
Speaker 1: And here's some more trivia for you if you're ever
Speaker 1: doing that pub trivia. You remember the first thing with
Speaker 1: the barcode was Wrigley's Chewing Gum. The first CD to
Speaker 1: ever be produced was the album fifty Second Street by
Speaker 1: Billy Joel. That album actually had some pretty good songs
Speaker 1: on it, uh, including my Life, which would later serve
Speaker 1: as the original theme song for the Tom Hanks sitcom
Speaker 1: Bosom Buddies. I guess you could probably tell that I'm
Speaker 1: I'm patting this episode out a little bit. But this
Speaker 1: is again useful information if you're ever playing pub trivia.
Speaker 1: So if you ever hear what was the first album
Speaker 1: produced on CD, you now know it's fifty second Street
Speaker 1: by Billy Joel. In nineteen seventy nine, Gould would finally
Speaker 1: receive a patent that covered a pretty wide range of
Speaker 1: laser applications, so that meant that he finally won the
Speaker 1: laser battle. You'll remember that in the previous section I
Speaker 1: talked about how he had applied for a patent but
Speaker 1: was essentially denied that patent because of a previous application
Speaker 1: that had taken the intellectual property Gould had created and notarized.
Speaker 1: So this was the end of a very long battle
Speaker 1: uh here well, at least as far as who has
Speaker 1: the legal right to claim the intellectual property of lasers.
Speaker 1: But it would be Shallow, who was one of the
Speaker 1: parties who had filed the other patent back in a
Speaker 1: couple of decades earlier, three decades earlier, and Blombergen, who
Speaker 1: had actually received the Nobel Prize in Physics in one
Speaker 1: for their work in laser spectroscopy. So people were doing
Speaker 1: well all around in the laser world. In the mid
Speaker 1: nineteen eighties, research laboratories began to use lasers to manipulate
Speaker 1: individual atoms, which is really cool. It opened up a
Speaker 1: brand new world in quantum uh science as well as
Speaker 1: just physical science. You may have seen the infamous picture
Speaker 1: of IBM spelling out its name and individual atoms that
Speaker 1: use lasers to position them. It's really pretty awesome. And
Speaker 1: by the late nineteen eighties Gould began to get royalties
Speaker 1: for his patents, so better late than never. In seven,
Speaker 1: Dr Stephen Truckle became the first doctor to use an
Speaker 1: ex semer laser to perform corrective surgery on a patient's eyes.
Speaker 1: This method was called the photo refractive care tectomy or
Speaker 1: pr K surgery. That would start a line of research
Speaker 1: and development in laser eye surgery in general, with lazic
Speaker 1: surgery debuting in ninete and I had lazy lazic surgery
Speaker 1: done just a few years ago. It corrected my vision. Uh.
Speaker 1: I talked about it on a podcast. Chris Pallette was
Speaker 1: on that one too, So you can do a search
Speaker 1: on tech stuffs archives and hear all about laser eye surgery.
Speaker 1: And I think if you listen carefully enough you can
Speaker 1: actually hear Chris Pallette turned green in the episode. He
Speaker 1: does a lot of unpleasant sounds because it was clear
Speaker 1: he was not comfortable in that episode. I might have
Speaker 1: taken a little extra glee from that. Now, skipping way
Speaker 1: ahead to two thousand three, that was when researchers from
Speaker 1: NASA demonstrated that you could power an aircraft using lasers.
Speaker 1: The aircraft in question weighed just threeleven grams, not kilograms,
Speaker 1: just grams. It had a balsa would frame and had
Speaker 1: a wingspan of one and a half meters. Net used
Speaker 1: an electric motor that was powered by a photovoltaic cell,
Speaker 1: so like a solar cell, but in this case it
Speaker 1: was specifically accepting light from this laser which was firing
Speaker 1: in an invisible spectrum, so you couldn't see the laser,
Speaker 1: but you can direct it at the cell that would
Speaker 1: provide the energy needed to convert it over into electricity
Speaker 1: and us propel the aircraft, which pretty cool. And today
Speaker 1: there are tons of uses of lasers, and some of
Speaker 1: them are released silly, like you know, they're being sold
Speaker 1: as cat toys and dog toys at this point, but
Speaker 1: some are really serious or things that are used in
Speaker 1: the medical field, for engineering, for industry, and we're looking
Speaker 1: at the possibility of even using them to propel spacecraft
Speaker 1: to other star systems, which is a really neat idea.
Speaker 1: This is based on the idea of the solar sail,
Speaker 1: where you have a spacecraft and it has a sale
Speaker 1: that you can direct light toward, and light has momentum.
Speaker 1: It's got relativistic momentum, So a photon does not have
Speaker 1: a lot of momentum by itself, but a stream of
Speaker 1: photons directed at a surface for long enough does have
Speaker 1: a physical push to it. And as it turns out,
Speaker 1: if you build very tiny spacecraft with a decent light sale,
Speaker 1: and you use a laser on Earth. You can continuously
Speaker 1: accelerate that spacecraft over time so that it reaches incre
Speaker 1: edible speeds. Now that acceleration is going to be at
Speaker 1: a low rate, so it doesn't speed up immediately, but
Speaker 1: it will over time get faster and faster and faster.
Speaker 1: And in fact, this is what some people are suggesting
Speaker 1: we do to send spacecraft to the nearest star system
Speaker 1: are the one that's nearest to our own That would
Speaker 1: be the Alpha Centauri system, and Proxima B would be
Speaker 1: the place we would really want to take a look at.
Speaker 1: That's the the planet around Proximates Centauri that's the closest
Speaker 1: to our solar system, that is the most earthlike in nature.
Speaker 1: And so there are some people saying, why don't we
Speaker 1: release swarms of tiny spacecraft using these sort of light sales,
Speaker 1: use lasers to direct them towards the Alpha Centauri system.
Speaker 1: And because of the incredible speeds they can reach, they
Speaker 1: can get to the Centauri system within about twenty years.
Speaker 1: That's incredible because the Centauri systems four light years away.
Speaker 1: That means it takes four years for light to get there,
Speaker 1: to hear, so to get there in twenty years using
Speaker 1: a physical spacecraft. You're moving at a really good clip. Now,
Speaker 1: granted at that speed, you're also just zooming by the
Speaker 1: Centauri system. You're not stopping for tea or anything, but
Speaker 1: still pretty cool idea that lasers could play an instrumental
Speaker 1: role in getting us to a different star system, or
Speaker 1: at least getting our eyes to a different star system.
Speaker 1: No humans would be traveling on those spacecraft. Well, that
Speaker 1: about wraps it up for this episode on Pupil Lasers.
Speaker 1: I hope you guys enjoyed it. I'll be talking about
Speaker 1: lots of other cool technology and upcoming episodes, so make
Speaker 1: sure you stay tuned to that. If you have any
Speaker 1: suggestions for future episodes, whether it's a topic or a
Speaker 1: guest I should have on the show, or someone you
Speaker 1: would love to have as a as a co host
Speaker 1: for an episode or two, let me know. Send me
Speaker 1: an email. The address is tech Stuff at how stuff
Speaker 1: works dot com, or you can drop me a line
Speaker 1: on social media on Facebook and Twitter. The show's handle
Speaker 1: is text stuff h s W as all as. You
Speaker 1: can also tune into twitch dot tv slash tech stuff
Speaker 1: on Wednesdays and Fridays to watch me stream the show live,
Speaker 1: where not only do you get to hear an episode early,
Speaker 1: you get to hear all the mistakes, you get to
Speaker 1: banter with me between segments, and you might even hear
Speaker 1: me tell horrible jokes at the end of an episode.
Speaker 1: So go to twitch dot tv slash tech stuff to
Speaker 1: see the schedule and join me there sometime. I'd love
Speaker 1: to see you until next time. I'll talk to you
Speaker 1: guys again, really soon. For more on this and thousands
Speaker 1: of other topics because it how stuff works, dot com