WEBVTT - Powerful Lasers and Their Uses 0:00:04.120 --> 0:00:07.120 Get in touch with technology with tech Stuff from how 0:00:07.200 --> 0:00:13.840 stuff Works dot com. Hey there, and welcome to tech Stuff. 0:00:13.880 --> 0:00:17.040 I'm your host, Jonathan Strickland. I'm an executive producer with 0:00:17.079 --> 0:00:19.160 how Stuff Works in a lot of all things tech, 0:00:19.800 --> 0:00:22.479 and today we're going to revisit a topic I have 0:00:22.600 --> 0:00:25.959 talked about numerous times. I've covered the topic of lasers 0:00:26.040 --> 0:00:28.680 on quite a few episodes of tech Stuff. In fact, 0:00:28.960 --> 0:00:30.840 if you've been listening long enough, you know I used 0:00:30.840 --> 0:00:37.240 to always bust out the laser kind of dr evil 0:00:37.240 --> 0:00:39.839 pronunciation at least once in every episode. So we got 0:00:39.840 --> 0:00:41.760 that all the way good to know we can go 0:00:41.880 --> 0:00:45.120 right into the actual meat of this episode. So I 0:00:45.159 --> 0:00:48.239 thought today we were going to cover some specific lasers 0:00:48.640 --> 0:00:52.559 and explain what people are doing with those lasers. And 0:00:52.560 --> 0:00:54.480 I think most of us are familiar with the general 0:00:54.520 --> 0:00:57.040 concept of lasers, but we're gonna talk a little bit 0:00:57.080 --> 0:00:59.760 about how they work because it's important to understand the 0:00:59.760 --> 0:01:04.080 Bay six in order to get a deeper appreciation for 0:01:04.319 --> 0:01:06.800 the high powered lasers I'm going to talk about today, 0:01:06.800 --> 0:01:09.280 because we're talking about some of the most powerful lasers 0:01:09.360 --> 0:01:13.039 in the world in this episode. So lasers are focused 0:01:13.080 --> 0:01:16.319 beams of light they're used in you know, wicked light 0:01:16.360 --> 0:01:20.119 shows like with Pink Floyd, or they're used to frustrate 0:01:20.160 --> 0:01:23.760 household pets. In science fiction, they're used either by or 0:01:23.800 --> 0:01:28.279 against robots and aliens or both. In the real world, 0:01:28.720 --> 0:01:32.360 they're used for all sorts of stuff, from conducting experiments too, 0:01:33.200 --> 0:01:34.880 in order to learn more about stuff like you know, 0:01:34.959 --> 0:01:39.520 quantum effects, all the way to you know, removing unwanted hair. Now, 0:01:39.560 --> 0:01:41.880 it would not be an episode of tech stuff if 0:01:41.920 --> 0:01:44.080 I didn't take the opportunity to at least go over 0:01:44.080 --> 0:01:46.240 the basics of how a laser works. So tuck in 0:01:46.360 --> 0:01:50.960 here we go. The word laser used to be an acronym, 0:01:51.000 --> 0:01:54.120 so I guess technically it's still kind of is an acronym, 0:01:54.240 --> 0:01:57.400 but we recognize laser as being a noun all on 0:01:57.480 --> 0:01:59.480 its own, so you don't have to capitalize all the 0:01:59.520 --> 0:02:02.000 letters the way you would with a typical acronym. The 0:02:02.120 --> 0:02:07.880 letters do stand for light amplification by stimulated emission of radiation. 0:02:07.960 --> 0:02:11.360 But what the heck does that mean? All right, this 0:02:11.480 --> 0:02:14.640 requires us to go back into some basic elementary school 0:02:14.680 --> 0:02:18.400 science stuff. You remember the structure of an atom, right, 0:02:18.480 --> 0:02:20.480 you that you got the nucleus in the middle. It's 0:02:20.480 --> 0:02:24.480 made up of protons and neutrons. Around that nucleus orbit 0:02:24.639 --> 0:02:28.919 one or more electrons, depending upon which element you're talking about, 0:02:29.000 --> 0:02:31.760 whether or not it's an ion, the electrons and have 0:02:31.919 --> 0:02:35.800 it a space around the nucleus that we call the 0:02:35.800 --> 0:02:39.680 electrons orbital or its energy shell or energy level. So 0:02:39.720 --> 0:02:44.480 electrons can only have certain discrete values of energy. They 0:02:44.480 --> 0:02:50.280 cannot be you know, any value between two. It's one value, 0:02:50.320 --> 0:02:53.080 and then the next layer level up is another value, 0:02:53.080 --> 0:02:56.519 and so on. They are discreet. Each energy shell can 0:02:56.560 --> 0:03:00.960 only hold a certain number of electrons. The shell closest 0:03:01.080 --> 0:03:03.560 to the nucleus is what we would call the K 0:03:03.840 --> 0:03:07.680 shell or the one shell. It can hold two electrons. 0:03:08.639 --> 0:03:11.600 Next out is an orbital that can hold an additional 0:03:11.840 --> 0:03:14.239 six electrons, so now you have up to eight total. 0:03:14.520 --> 0:03:17.800 The third shell can hold an additional ten electrons, so 0:03:17.880 --> 0:03:22.120 you could have a possibility of eighteen electrons with three 0:03:22.120 --> 0:03:26.760 electron shells are orbiting an atom or nucleus, I should 0:03:26.760 --> 0:03:30.240 say not not orbiting an atom, because the atoms the 0:03:30.240 --> 0:03:34.600 whole thing. Anyway, each of those energy shells are important. 0:03:34.600 --> 0:03:38.120 It tells you the ground state for any given electron. 0:03:38.360 --> 0:03:41.560 It will always be at the lowest energy shell it 0:03:41.680 --> 0:03:45.040 can inhabit. So if an energy shells full, so if 0:03:45.080 --> 0:03:47.840 that burst energy shells full, the electron has to be 0:03:47.840 --> 0:03:51.480 in the second shell or or higher, depending on how 0:03:51.520 --> 0:03:55.560 many there are there. Now, if you add energy to 0:03:55.720 --> 0:03:59.000 an atom, that energy would cause those electrons to move 0:03:59.040 --> 0:04:02.640 into higher in G shells, to move further out from 0:04:02.720 --> 0:04:06.440 the nucleus. So if you pump energy into atoms, the 0:04:06.480 --> 0:04:09.320 electrons begin to move further out. And if you pump 0:04:09.480 --> 0:04:12.880 enough energy, and you could actually strip electrons away from atoms, 0:04:12.920 --> 0:04:16.039 at least temporarily, but you would then have a charged 0:04:16.200 --> 0:04:19.240 nucleus and you probably have some free electrons running everywhere. 0:04:19.240 --> 0:04:21.840 They would quote unquote want to get back together because 0:04:21.839 --> 0:04:25.360 those opposite charges would attract one another. But what happens 0:04:25.360 --> 0:04:29.719 if you stop adding energy to the atom, Well, the 0:04:29.800 --> 0:04:35.560 electrons will return to their normal ground energy states. However, 0:04:36.240 --> 0:04:39.159 they cannot do that while still holding on to that 0:04:39.520 --> 0:04:42.240 energy you pumped into them. So first they have to 0:04:42.320 --> 0:04:46.039 release that excess energy in some way, and electrons do 0:04:46.160 --> 0:04:50.960 this by releasing photons, the particles of light. That's one 0:04:51.040 --> 0:04:54.000 part that's really important to remember with lasers. The other 0:04:54.040 --> 0:04:58.240 big important thing to remember is that frequency or wavelength, 0:04:58.360 --> 0:05:02.000 and thus the color of light released is dependent upon 0:05:02.120 --> 0:05:05.480 both the lasing medium itself, what that material is made 0:05:05.480 --> 0:05:09.080 out of, and the energy difference between the excited state 0:05:09.200 --> 0:05:12.159 of the electron and its ground state. How much energy 0:05:12.200 --> 0:05:16.200 did you pour into this thing. Different atoms will release 0:05:16.279 --> 0:05:20.880 different frequencies or colors of light. So, for example, if 0:05:20.920 --> 0:05:25.200 you excite the electrons in a ruby lazing medium that 0:05:25.279 --> 0:05:28.240 has a lot of chromium ions in it, it will 0:05:28.320 --> 0:05:31.840 produce a red light assuming you're doing the normal amount 0:05:31.839 --> 0:05:35.440 of energy pouring into this. Other lasing media will produce 0:05:35.520 --> 0:05:38.760 different wavelengths of light and thus different colors. That can 0:05:38.800 --> 0:05:41.800 include light that's actually outside the visible spectrum, so you 0:05:41.839 --> 0:05:45.279 can have lasers that are infrared lasers or ultraviolet lasers. 0:05:45.600 --> 0:05:48.320 Those would be invisible to the human eye. But as 0:05:48.400 --> 0:05:51.520 I mentioned, the wavelength also also depends upon how much 0:05:51.600 --> 0:05:54.400 energy you pumped into the electrons before they return to 0:05:54.440 --> 0:05:57.640 their ground state. Now, unlike the light we would get 0:05:57.760 --> 0:06:01.240 from an incandescence source like a light bulb, all the 0:06:01.279 --> 0:06:04.640 photons from a lasing medium will be of the exact 0:06:04.800 --> 0:06:09.480 same wavelength, so they'll all be the same color. Moreover, 0:06:09.960 --> 0:06:14.400 the photons are in are are coherent. That means that 0:06:14.960 --> 0:06:17.200 if you were to chart the waves of a laser, 0:06:17.680 --> 0:06:20.760 all the photons would match up with their crests and 0:06:20.839 --> 0:06:25.040 troughs in lockstep with one another. Normal visible light consists 0:06:25.080 --> 0:06:28.480 of photons of different wavelengths and they are not coherent. 0:06:28.520 --> 0:06:33.080 They are not moving at the same lockstep pace. The 0:06:33.160 --> 0:06:36.200 coherence of a laser allows it to remain focused in 0:06:36.240 --> 0:06:40.400 a tight beam over great distances. Directionality is another important 0:06:40.839 --> 0:06:44.800 fact factor with lasers. Now that's in sharp contrast to 0:06:44.839 --> 0:06:48.599 the light from an incandescence source, which is diffuse not coherent. 0:06:49.279 --> 0:06:53.720 For your typical, you know, laboratory laser, the way you 0:06:53.760 --> 0:06:57.160 would stimulate the lasing medium is you would expose the 0:06:57.240 --> 0:07:01.840 lasing medium to an extremely intent flash of white light 0:07:01.960 --> 0:07:06.160 from powerful flash lamps for a fraction of a second. Typically, 0:07:06.520 --> 0:07:09.640 this is called pumping the lasing medium. As you are 0:07:09.680 --> 0:07:14.400 pouring energy into the medium the collection of atoms and 0:07:14.440 --> 0:07:18.120 thus exciting the electrons in those atoms to higher energy states, 0:07:18.440 --> 0:07:22.280 and when they come back down they release these photons 0:07:22.320 --> 0:07:26.640 of the same wavelength and energy level. This process happens 0:07:26.680 --> 0:07:29.520 so fast that it's really hard to wrap your mind 0:07:29.560 --> 0:07:31.720 around it all or at least, it's very hard for 0:07:31.760 --> 0:07:34.440 me to do that because we're talking about times that 0:07:34.480 --> 0:07:38.000 are at one million of a second or even shorter 0:07:38.080 --> 0:07:41.320 than that. So typically the goal is to excite electrons 0:07:41.360 --> 0:07:45.320 to an energy level two or three levels higher than 0:07:45.360 --> 0:07:48.920 their normal ground state. That increases what is called the 0:07:49.040 --> 0:07:53.160 population inversion. That is the relationship between the number of 0:07:53.200 --> 0:07:56.360 atoms that are in an excited state compared to those 0:07:56.440 --> 0:08:00.320 in the ground state. So we call it inverted because 0:08:00.320 --> 0:08:04.360 typically most atoms are in a ground state, but now 0:08:04.400 --> 0:08:07.840 we've inverted that where most atoms are in an excited state. 0:08:08.360 --> 0:08:11.080 As the electrons calm the heck down, they release these 0:08:11.080 --> 0:08:14.760 photons of the same wavelength. Since that lasing medium is 0:08:14.760 --> 0:08:17.480 obviously made out of all the same stuff, these photons 0:08:17.520 --> 0:08:21.040 are locked together, so their wavefront's launching unison. That's what 0:08:21.120 --> 0:08:24.000 makes them coherent, and they are very directional. And this 0:08:24.120 --> 0:08:28.240 happens because of the stimulated emission part of lasers. So 0:08:28.560 --> 0:08:31.800 you've got an excited electron, it returns to its ground state, 0:08:31.880 --> 0:08:35.240 it releases a photon of a certain wavelength. If that 0:08:35.280 --> 0:08:38.840 photon happens to run into an atom that also has 0:08:38.880 --> 0:08:42.200 an electron that was in that same excited state, the 0:08:42.240 --> 0:08:45.840 photon can stimulate that atom so that the photon the 0:08:45.920 --> 0:08:49.439 atom will emit when it's electron returns to its ground state, 0:08:50.000 --> 0:08:52.240 is going to vibrate the same as that first photon, 0:08:52.360 --> 0:08:54.559 and it will also move in the same direction as 0:08:54.600 --> 0:08:58.680 that first photon. Mirrors make up another important component in 0:08:58.720 --> 0:09:02.160 your typical laser. So let's think of a very simple laser. 0:09:02.200 --> 0:09:06.080 Imagine you've got a tube and this tube is your laser. 0:09:06.800 --> 0:09:10.240 On either end of the tube, you have mirrors that 0:09:10.280 --> 0:09:13.520 are facing into the tube's center, and in the middle 0:09:13.559 --> 0:09:16.199 of the tube, you've got the lazing medium and you've 0:09:16.240 --> 0:09:21.920 got a big flash lamp pointed at this tube and 0:09:22.040 --> 0:09:27.720 it can shoot extremely intense white light at the lasing medium, 0:09:27.920 --> 0:09:33.600 which then ends up inducing this this uh laser to 0:09:33.800 --> 0:09:37.560 to begin this this you know, this stimulated a mission 0:09:37.600 --> 0:09:41.640 process to begin, and so you get photons that are 0:09:41.720 --> 0:09:45.680 emitted by these excited atoms. They traveled down the tube, 0:09:45.840 --> 0:09:48.959 they hit a mirror, bounces back, and it passes through 0:09:49.000 --> 0:09:52.559 the lasing medium again and that gives it the opportunity 0:09:52.640 --> 0:09:55.079 to stimulate some more of the atoms that they too 0:09:55.120 --> 0:09:59.760 will release photons that will be in the same um wayfront, 0:10:00.200 --> 0:10:04.720 same direction as the initial photons. They'll continue down the tube, 0:10:04.880 --> 0:10:08.360 hit the mirror, bounce back, and this creates a cascade 0:10:08.360 --> 0:10:13.000 effect that can create more and more photons generating through 0:10:13.040 --> 0:10:16.360 this laser. Now, one of those two mirrors is what 0:10:16.400 --> 0:10:19.679 we would call half silvered, which means the mirror will 0:10:19.720 --> 0:10:22.800 actually allow some of that light to pass through a 0:10:22.920 --> 0:10:25.920 reflecting the rest of it back in. So some of 0:10:25.920 --> 0:10:29.280 the laser light escapes through that and then can be 0:10:29.920 --> 0:10:33.200 in a focused beam, while other photons would still bounce 0:10:33.200 --> 0:10:36.200 back into the tube and continue the propagation of photons. 0:10:36.240 --> 0:10:39.439 So that's how lasers work. From a very very high level. 0:10:39.520 --> 0:10:41.920 There are a lot of different details we could get into, 0:10:42.320 --> 0:10:44.120 like the fact that there are so many different types 0:10:44.120 --> 0:10:50.120 of lasing media like their solid state, there's gas lasing media, etcetera, etcetera. 0:10:50.200 --> 0:10:55.680 But what makes one laser more powerful than another, Well, 0:10:56.840 --> 0:10:59.640 that's a tricky question. What makes one laser a fun 0:10:59.720 --> 0:11:02.840 toy a like a laser pointer and another one powerful 0:11:02.920 --> 0:11:06.520 enough to etch metal? Well, first, the energy level of 0:11:06.520 --> 0:11:11.280 photons produced by a lasing material is inversely proportional to 0:11:11.400 --> 0:11:14.880 the wavelength of the light produced when it is stimulated. 0:11:14.880 --> 0:11:17.920 When that lasing material is stimulated, So the higher the 0:11:18.040 --> 0:11:22.840 energy of the photon, the shorter the wavelength of that photon, 0:11:23.760 --> 0:11:27.200 and the wavelengths of visible light range from around the 0:11:27.280 --> 0:11:32.400 three range that would be in the violet part of 0:11:32.400 --> 0:11:35.920 the spectrum all the way up to seven nimes which 0:11:35.960 --> 0:11:37.720 would be in the red part of the spectrum. So 0:11:38.280 --> 0:11:41.960 the further down roy g BIV you go, the higher 0:11:42.000 --> 0:11:46.040 the energy levels of the associated photons. So one thing 0:11:46.040 --> 0:11:49.560 that determines the power of a laser is the energy 0:11:49.640 --> 0:11:52.520 level of the photons, which depends upon the lasing medium 0:11:52.679 --> 0:11:55.600 and the amount of energy you're pouring into that medium 0:11:55.720 --> 0:11:58.240 to produce the laser in the first place. So your 0:11:58.240 --> 0:12:01.800 power source is another factor to consider, and there's also 0:12:01.840 --> 0:12:05.520 the question of whether your laser is constant or a 0:12:05.600 --> 0:12:09.800 pulse laser that also affects the power of the laser beam. 0:12:09.840 --> 0:12:12.520 I'll talk more about pulse lasers a little bit later 0:12:12.520 --> 0:12:15.760 in this episode because it's a very important component of 0:12:16.000 --> 0:12:19.439 the really powerful lasers we're going to talk about. So 0:12:19.840 --> 0:12:22.600 when we come back, I'm going to start talking about 0:12:22.640 --> 0:12:25.120 some of these really powerful lasers and what they're used for. 0:12:25.160 --> 0:12:28.680 But first let's take a quick break to thank our sponsor. 0:12:36.360 --> 0:12:41.480 At the University of Nebraska, there is an extreme Light laboratory, 0:12:41.880 --> 0:12:44.880 and in that lab there's an enormous device called the 0:12:45.160 --> 0:12:49.599 Diacles laser. It's named after the inventor of the parabolic reflector. 0:12:50.120 --> 0:12:54.679 The parabolic reflector increases the intensity of reflected light. It's 0:12:54.720 --> 0:12:57.800 the most efficient way of doing it, the most powerful 0:12:57.840 --> 0:13:01.480 way of increasing the intensity of selected light that we've 0:13:01.480 --> 0:13:07.520 ever discovered. So according to the labs website quote, Diacles 0:13:07.840 --> 0:13:11.400 begins with a modest amount of energy with a short pulse, 0:13:11.880 --> 0:13:14.960 then stretches the pulse and sends it through a series 0:13:15.000 --> 0:13:19.840 of amplifiers and titanium sapphire crystals to pump up its power. 0:13:20.160 --> 0:13:23.760 The secret to Diacles is high power. Is a compression 0:13:23.840 --> 0:13:28.160 stage where the stretched amplified pulse is compressed back into 0:13:28.200 --> 0:13:32.560 a very short, extremely powerful pulse. This trick prevents damage 0:13:32.559 --> 0:13:35.800 to the amplifiers. Then the powerful beam hits a parabolic 0:13:35.840 --> 0:13:40.560 reflector that focuses its power to extreme intensities. I'll go 0:13:40.640 --> 0:13:43.640 more into this approach a little bit later with one 0:13:43.640 --> 0:13:46.800 of the other lasers, but the result of this is 0:13:46.840 --> 0:13:49.240 that you get a laser beam so powerful that it 0:13:49.320 --> 0:13:53.920 reportedly can produce light that is one billion times brighter 0:13:54.160 --> 0:13:57.560 than the light produced at the surface of the Sun itself. 0:13:58.200 --> 0:14:00.920 So what would you use the kind of a laser for. 0:14:01.440 --> 0:14:04.280 Would you use it to to blast a planet into 0:14:04.280 --> 0:14:10.880 a billion pieces because it was in Alderon places rim shot. No, 0:14:11.160 --> 0:14:14.079 because that would actually require way more energy than even 0:14:14.160 --> 0:14:19.280 this beast could produce. The DIACLES is designed for scientific research, 0:14:19.360 --> 0:14:24.320 particularly in the realm of studying the interactions between light 0:14:24.600 --> 0:14:27.920 and matter. It's mostly used in an area called high 0:14:28.040 --> 0:14:32.120 field science. So what the heck is that? Well, the 0:14:32.160 --> 0:14:34.400 University of Nebraska is not the only place that does this. 0:14:34.480 --> 0:14:36.880 There's also the University of Michigan. They have a Center 0:14:36.920 --> 0:14:40.960 for Ultra Fast Optical Science. They break down high field 0:14:41.000 --> 0:14:45.920 science as science revolving around conditions that include high energy density, 0:14:46.120 --> 0:14:50.560 and that involves getting a better understanding of non equilibrium 0:14:50.600 --> 0:14:55.000 systems as well as a deeper understanding of electron behaviors. 0:14:55.040 --> 0:14:58.160 So this has the potential to have many different applications 0:14:58.160 --> 0:15:02.400 in the future relating to cool stuff nanotechnology. Plus, well, 0:15:03.040 --> 0:15:05.120 we don't even know what we don't know yet, so 0:15:05.160 --> 0:15:07.480 we might find other really nifty things to do with it. 0:15:08.160 --> 0:15:12.080 One thing, this laser can do right now? Is vapor 0:15:12.200 --> 0:15:15.840 us stuff real good? Actually, I should say it can 0:15:15.880 --> 0:15:20.120 excite matter to convert it to plasma. Plasma is the 0:15:20.160 --> 0:15:24.680 most plentiful form of matter in the universe. Matter heats 0:15:24.760 --> 0:15:29.920 up to incredible temperatures under the intensity of this laser, 0:15:30.480 --> 0:15:35.520 and it also has its pressure increased dramatically, and at 0:15:35.560 --> 0:15:39.640 that point the material converts into a gas through which 0:15:39.840 --> 0:15:45.000 free electrons can flow. That is plasma. So plasma is 0:15:45.040 --> 0:15:46.440 sort of you can think of it as almost a 0:15:46.480 --> 0:15:50.240 subtype of gas. It's more than just gas because you 0:15:50.280 --> 0:15:52.880 have this condition where you have high energy in there, 0:15:52.880 --> 0:15:55.240 so you've got a lot of free electrons flowing around. 0:15:55.560 --> 0:16:00.600 You have a typically a net neutral electric charge plasma, 0:16:00.640 --> 0:16:04.680 but it means it can actually conduct electricity itself. This 0:16:04.760 --> 0:16:09.040 is the stuff of stars. Stars are made of plasma, 0:16:09.120 --> 0:16:14.920 So you're talking incredibly high temperatures and pressures in the 0:16:15.040 --> 0:16:19.480 research team at Nebraska used this particular laser to conduct 0:16:19.560 --> 0:16:22.680 a super interesting experiment. They wanted to find out what 0:16:22.720 --> 0:16:27.400 would happen if you bombarded the same electron with numerous photons. 0:16:28.560 --> 0:16:32.680 And this is I have to stress wicked hard to do. 0:16:33.400 --> 0:16:37.600 An electron is a pretty darn tiny target. Now. I'm 0:16:37.640 --> 0:16:39.600 not going to get into the size of electrons here 0:16:39.640 --> 0:16:43.640 because that alone is a complicated issue and involves things 0:16:43.680 --> 0:16:46.560 like wave functions. But anyway, it's it's really really super small. 0:16:46.920 --> 0:16:51.520 Near typical electron rarely encounters a photon. It might get 0:16:51.560 --> 0:16:55.920 struck by a photon three times a year, so every 0:16:55.960 --> 0:16:59.520 four months or so, this electron might run into a photon, 0:16:59.560 --> 0:17:03.520 but otherwise eyes know. The team, however, wanted to pelt 0:17:03.560 --> 0:17:06.480 the heck out of electrons. They wanted to study the 0:17:06.520 --> 0:17:11.040 scatter effect that the electron would have on photons. The 0:17:11.080 --> 0:17:13.800 scatter effect is what happens when light strikes a surface. 0:17:13.840 --> 0:17:16.679 The light scatters after it hits a surface, and our 0:17:16.720 --> 0:17:20.200 eyes can pick that light up, and that's how vision works. 0:17:20.520 --> 0:17:22.800 You can see stuff because light scatters off of it 0:17:22.840 --> 0:17:26.920 in various ways. Now, the team was doing the same thing, 0:17:27.000 --> 0:17:29.399 except instead of using a general light source like a 0:17:29.480 --> 0:17:32.639 lamp and a macro sized object like say a couch 0:17:32.760 --> 0:17:36.280 or something, they were using this super powerful laser as 0:17:36.320 --> 0:17:40.639 the light source an electron beam as their target. Now, 0:17:40.640 --> 0:17:43.959 according to the University of Nebraska's newspaper, the team was 0:17:44.000 --> 0:17:49.640 able to scatter nearly one thousand photons off the same electron, 0:17:50.160 --> 0:17:52.919 and according to the team, the behavior of both the 0:17:52.960 --> 0:17:58.440 photons and the electron fell outside the normal reactions, which 0:17:58.480 --> 0:18:01.840 is pretty interesting in science. Anything that is outside the 0:18:01.880 --> 0:18:06.280 normal result is interesting. Now, if you're unlucky, if you 0:18:06.359 --> 0:18:09.719 haven't been super careful or or something has gone wrong, 0:18:10.040 --> 0:18:14.640 your observations might be indicative of an experimental error somewhere, 0:18:15.000 --> 0:18:17.919 like maybe you made a mistake, maybe some of your 0:18:17.920 --> 0:18:20.720 equipment wasn't working. But if you are lucky, you did 0:18:20.760 --> 0:18:23.919 everything properly, all your equipment works. What you were actually 0:18:23.920 --> 0:18:27.840 seeing is legitimately a new observation of a real phenomenon. 0:18:28.359 --> 0:18:31.199 So the team discovered that once laser light passed a 0:18:31.320 --> 0:18:35.640 certain power threshold, it would scatter off of electrons in 0:18:35.640 --> 0:18:40.240 interesting ways. Now, typically light from a source will scatter 0:18:40.320 --> 0:18:43.800 in a predictable way at the same angle and energy 0:18:43.840 --> 0:18:47.520 it possessed before the collision, no matter how intense the light. 0:18:47.960 --> 0:18:50.320 So think of it as a dimmer switch. If you 0:18:50.560 --> 0:18:54.480 have a dimmer switch on installed, and you're looking at 0:18:54.600 --> 0:18:58.520 say a table and low light, As you intensify the light, 0:18:58.680 --> 0:19:01.639 the table's shape doesn't change, its color doesn't change, it 0:19:01.760 --> 0:19:05.160 it brightens, so you might get more of a view 0:19:05.160 --> 0:19:07.280 of what the color is, but it doesn't change in 0:19:07.280 --> 0:19:12.240 any real phenomenal way. Uh, that was not what they 0:19:12.280 --> 0:19:15.520 were seeing. They were getting a totally different result. So 0:19:15.680 --> 0:19:18.359 if we could scale this up like their results and 0:19:18.480 --> 0:19:21.399 observe it with our eyeballs instead of with super sensitive 0:19:22.119 --> 0:19:24.560 you know, sensors, it would mean that if you were 0:19:24.600 --> 0:19:27.520 to use that same dimmer switch, you could see that 0:19:27.680 --> 0:19:31.439 as you turned the light past a certain level of intensity, 0:19:32.000 --> 0:19:34.879 the thing you're looking at that table would actually appear 0:19:34.960 --> 0:19:39.400 to change shape and color because you were using light 0:19:39.600 --> 0:19:42.520 that was of that great intensity. That's essentially what they found, 0:19:42.560 --> 0:19:46.160 except again, they weren't using diffuse light. They were using 0:19:46.400 --> 0:19:50.000 a super focused, very high powered laser, and they weren't 0:19:50.080 --> 0:19:52.520 looking at a macro object. They were looking at electrons. 0:19:53.280 --> 0:19:56.040 The team also observed that the electron being pummeled by 0:19:56.080 --> 0:20:00.000 photons would release its own photon, so the electron would 0:20:00.040 --> 0:20:03.960 become stimulated in other words, but that this ejected photon 0:20:04.160 --> 0:20:07.840 would begin to absorb the energy of the scattered photons 0:20:08.119 --> 0:20:12.000 from the laser. This transformed the energy and wavelength of 0:20:12.040 --> 0:20:16.239 the ejected photon, and it would turn into an X ray. Now, 0:20:16.240 --> 0:20:18.960 according to the researchers. Such an X ray could have 0:20:19.080 --> 0:20:23.639 useful applications in nanotechnology. The X ray only lasts for 0:20:23.720 --> 0:20:26.480 a short moment, but has an extreme amount of energy, 0:20:26.840 --> 0:20:29.639 and it could be used to help create three dimensional 0:20:29.720 --> 0:20:33.000 images of stuff on the nanoscopic scale, and that would 0:20:33.000 --> 0:20:37.040 be phenomenal because the nanoscale is so small that at 0:20:37.040 --> 0:20:39.240 the lower end of it, you're dealing with stuff that's 0:20:39.240 --> 0:20:42.520 actually smaller than the wavelength of visible light, which is 0:20:42.720 --> 0:20:45.880 why you cannot use an optical microscope to look at 0:20:45.880 --> 0:20:48.600 stuff that's on the nanoscale. The wavelengths of light are 0:20:48.640 --> 0:20:51.040 just too big to pick up the objects you're actually 0:20:51.040 --> 0:20:54.200 looking for, so that's kind of crazy. But this could 0:20:54.200 --> 0:20:59.400 potentially allow people to create three dimensional visualizations of objects 0:20:59.440 --> 0:21:02.200 that are on the scale. It could also have other 0:21:02.200 --> 0:21:05.520 practical applications, including medical ones. It could allow X ray 0:21:05.560 --> 0:21:09.400 technicians to create images at a much higher resolution, which 0:21:09.440 --> 0:21:12.919 would be really useful to look for stuff like micro fractures. 0:21:13.040 --> 0:21:15.919 For example, the standard X ray machine might not be 0:21:15.960 --> 0:21:18.800 able to detect because it wouldn't have that level of resolution. 0:21:19.280 --> 0:21:21.400 It could also be used in other applications, such as 0:21:21.400 --> 0:21:24.480 in security systems to scan for potential weapons or other 0:21:24.520 --> 0:21:28.439 security threats, and it's increasing our understanding of physics in general, 0:21:28.520 --> 0:21:31.800 which could lead to practical applications we can't even anticipate. 0:21:32.480 --> 0:21:35.200 So that's Diacles. But we have more to talk about 0:21:35.240 --> 0:21:38.080 in just a moment. Let's take a quick break to 0:21:38.160 --> 0:21:49.200 thank our sponsor. Earlier I mentioned the University of Michigan's 0:21:49.200 --> 0:21:53.320 Center for Ultra Fast Optical Science. That's the home of 0:21:53.359 --> 0:21:58.479 another incredibly powerful laser. This one is called the Hercules laser. 0:21:58.880 --> 0:22:02.320 It's a high field pedal what class laser? A pedal? What, 0:22:02.440 --> 0:22:07.280 by the way, is a billion million whats and a 0:22:07.400 --> 0:22:10.760 what corresponds to the power and electric circuit in which 0:22:10.840 --> 0:22:13.600 the potential difference is one vault and the current is 0:22:13.640 --> 0:22:18.440 one amp here. So we're talking very high energy laser here. 0:22:18.880 --> 0:22:21.439 This laser is used in the LABS research programs to 0:22:21.560 --> 0:22:27.119 quote explore the ultra relativistic intensity regime of laser matter interaction. 0:22:27.200 --> 0:22:32.200 In to quote, huh, what the heck does ultra relativistic mean? 0:22:32.720 --> 0:22:35.400 While as you might guess, it does refer to the 0:22:35.400 --> 0:22:38.840 theory of relativity, A particle is said to be ultra 0:22:39.080 --> 0:22:44.000 relativistic when it is advanced to the speed that's really 0:22:44.040 --> 0:22:45.919 close to the speed of light when you get it 0:22:46.040 --> 0:22:48.359 super super fast, about as close to the speed of 0:22:48.440 --> 0:22:51.640 lights you can possibly manage. Einstein, of course, told us 0:22:51.880 --> 0:22:54.600 the speed of light is essentially the speed limit for 0:22:54.680 --> 0:22:58.320 all the stuff in our universe. In two thousand seven, 0:22:58.480 --> 0:23:02.600 the engineering team at the University of Michigan generated a 0:23:02.680 --> 0:23:06.080 laser with the power of three hundred terra wats, and 0:23:06.119 --> 0:23:09.560 it started off an era of ultra powerful laser experiments. 0:23:09.880 --> 0:23:13.520 The team holds the world records for highest focused intensity 0:23:13.560 --> 0:23:18.240 of a laser and the amplified spontaneous emission temporal contrast. 0:23:19.480 --> 0:23:22.520 I have no idea what that second thing means, if 0:23:22.520 --> 0:23:25.520 I'm being honest, but it does sound wicked dope. Remember 0:23:25.520 --> 0:23:28.080 earlier when I talked about how a laser's power depends 0:23:28.160 --> 0:23:31.400 partly on whether it is pulsed or a constant. Well, 0:23:31.440 --> 0:23:34.920 the Hercules laser relies upon a type of amplification called 0:23:35.240 --> 0:23:40.159 chirped pulse amplification. So this gets super technical, and I, 0:23:40.240 --> 0:23:43.160 frankly I do not understand all of it. So we're 0:23:43.160 --> 0:23:46.280 gonna go super high level because that's all my primitive 0:23:46.280 --> 0:23:48.960 reptile brain can handle. I'm gonna do my best to 0:23:48.960 --> 0:23:52.199 explain it as I understand it. So many apologies to 0:23:52.320 --> 0:23:55.480 all the high high field physics experts out there, all 0:23:55.480 --> 0:23:58.159 the laser engineers out there, give me a whole lot 0:23:58.160 --> 0:24:01.720 of slacks. So the goal is to use very short 0:24:01.840 --> 0:24:06.080 pulses of energy to create this laser and then amplify 0:24:06.119 --> 0:24:09.439 those pulses to get an output energy level that typically 0:24:09.480 --> 0:24:13.080 would only come from a longer pulse of energy. Now, 0:24:13.080 --> 0:24:16.680 when I say short pulses, i'm talking crazy short. We're 0:24:16.680 --> 0:24:20.480 talking on the femto second scale. A fempto second, by 0:24:20.480 --> 0:24:23.840 the way, is one quadrillionth of a second. It's an 0:24:23.920 --> 0:24:27.800 incredibly short amount of time. The fempto second laser pulse 0:24:28.080 --> 0:24:31.399 that starts things off has a very high peak power 0:24:31.480 --> 0:24:33.920 level and as well as the other stuff that comes 0:24:33.920 --> 0:24:38.359 with that like electric fields and stuff. But these qualities 0:24:38.359 --> 0:24:44.200 actually make those super short pulses potentially harmful to laser 0:24:44.200 --> 0:24:47.960 components like optics, and it can also cause beam distortion. 0:24:48.800 --> 0:24:51.520 So your output, your goal for your output is to 0:24:51.520 --> 0:24:55.240 get the super high powered laser, but the energy representing 0:24:55.280 --> 0:24:59.679