WEBVTT - TechStuff Profile: Robert N. Hall 0:00:04.160 --> 0:00:07.520 Get in tech with technology with tech Stuff from stuff 0:00:07.520 --> 0:00:13.760 works dot com. Hey there, and welcome to tech Stuff. 0:00:13.800 --> 0:00:17.040 I'm your host, Jonathan Strickland. I'm an executive producer at 0:00:17.040 --> 0:00:20.800 how Stuff Works and I love all things tech. And 0:00:20.960 --> 0:00:26.599 on Christmas Day nineteen nineteen, Dr Robert N. Hall was 0:00:26.720 --> 0:00:30.520 born in New Haven, Connecticut. He would pass away on 0:00:30.640 --> 0:00:35.360 November seven, two thousand sixteen, at the age of nineties six. 0:00:35.760 --> 0:00:39.480 The New York Times would publish an obituary about Dr 0:00:39.560 --> 0:00:44.159 Hall on May tenth, two thousand eighteen, with the title 0:00:44.360 --> 0:00:49.480 Robert N. Hall, ninety six, whose inventions are everywhere? Is dead? 0:00:50.000 --> 0:00:54.120 What's so remarkable about this gentleman that necessitated an obituary 0:00:54.240 --> 0:00:57.880 in the New York Times nearly two years after he 0:00:57.960 --> 0:01:02.440 actually passed away? And I the late obituary anyway, Well, 0:01:02.480 --> 0:01:05.560 we're gonna learn about Dr Robert INN. Hall and his 0:01:05.720 --> 0:01:09.399 numerous inventions. Hall grew up in Connecticut, and when he 0:01:09.480 --> 0:01:12.640 was a boy, his uncle took him to a technical fair, 0:01:12.959 --> 0:01:16.920 kind of a science and engineering festival. His uncle considered 0:01:16.959 --> 0:01:20.240 himself something of an inventor, and he wanted to encourage 0:01:20.360 --> 0:01:24.720 Robert to explore topics of science and technology. And according 0:01:24.800 --> 0:01:27.880 to an interview that Dr Hall gave in two thousand four, 0:01:28.040 --> 0:01:31.160 he said, quote, he took me to a technology fair 0:01:31.200 --> 0:01:33.680 when I was a small boy in New Haven, Connecticut, 0:01:34.080 --> 0:01:37.600 and there were a lot of electrical exhibits. Bouncing steel 0:01:37.720 --> 0:01:40.600 ball bearings and tin can motors were spinning on a 0:01:40.640 --> 0:01:44.840 flat table stroboscopes. He got my attention. It seems like 0:01:44.920 --> 0:01:47.960 these were fascinating little things, and I would like to 0:01:47.960 --> 0:01:51.080 know how they worked. And he tried to explain them 0:01:51.120 --> 0:01:53.200 to me, and he showed me where to find books 0:01:53.200 --> 0:01:56.120 in the library. Later on, when I went to high school, 0:01:56.360 --> 0:01:59.360 my mom let me have a little laboratory in the bedroom, 0:01:59.560 --> 0:02:01.520 and I said, up a lot of experiments and see 0:02:01.560 --> 0:02:04.440 if I can duplicate a lot of these things. End quote. 0:02:04.600 --> 0:02:09.320 Hall continued his experiments and pursued his interest in the sciences. 0:02:09.360 --> 0:02:13.040 He initially focused on astronomy, which is a bit of 0:02:13.040 --> 0:02:15.800 a pun because he actually took it upon himself to 0:02:15.919 --> 0:02:22.000 build his own eight inch telescope, including grinding the mirrors himself. 0:02:22.520 --> 0:02:25.040 While in high school, he met with a recruiter for 0:02:25.160 --> 0:02:29.200 cal Tech or the California Technical Institute. This led to 0:02:29.320 --> 0:02:32.720 Hall taking some entrance exams for the school and he 0:02:32.800 --> 0:02:35.760 must have performed pretty well on those tests because he 0:02:36.000 --> 0:02:40.080 ended up with a scholarship to attend cal Tech. Hall 0:02:40.160 --> 0:02:44.120 studied science and engineering at school for three years, at 0:02:44.120 --> 0:02:47.040 which point he ran out of money and he had 0:02:47.080 --> 0:02:49.440 to take a year off to earn more. To finish 0:02:49.480 --> 0:02:53.160 out his studies. He got a job at lockeed Aircraft 0:02:53.240 --> 0:02:56.440 as a test engineer. This was just before the United 0:02:56.440 --> 0:02:59.600 States would be pulled into World War Two. After a 0:02:59.680 --> 0:03:02.520 year of working at Lockheed, he returned to cal Tech 0:03:02.760 --> 0:03:05.679 and finished out his studies, earning a degree in physics. 0:03:05.960 --> 0:03:10.320 Immediately upon graduation, he was recruited by GE that is, 0:03:10.440 --> 0:03:13.200 General Electric to come and work for them as a 0:03:13.240 --> 0:03:17.720 test engineer in Schenectady, New York. General Electric was the 0:03:17.760 --> 0:03:20.600 company that grew out of the merger of Thomas Edison's 0:03:20.680 --> 0:03:26.280 General Electric Company and the Thomas Houston Electric Company of Lynn, Massachusetts. 0:03:26.320 --> 0:03:30.040 Both Thomas Edison and Charles Coffin, who were the leaders 0:03:30.040 --> 0:03:33.320 of the two companies, had made numerous acquisitions in the 0:03:33.440 --> 0:03:38.480 late nineteenth century and grown their respective companies considerably. General 0:03:38.520 --> 0:03:42.920 Electric became a sizeable conglomerate the day it formed through 0:03:42.960 --> 0:03:47.160 this merger in the late eighteen nineties. In nineteen hundred, 0:03:47.440 --> 0:03:52.000 GE created its own industrial research laboratory. By the time 0:03:52.080 --> 0:03:55.160 Hall went to work for the company in nineteen forty two, 0:03:55.560 --> 0:04:00.680 GE was known for introducing several technological innovations. In nineteen 0:04:00.720 --> 0:04:04.280 thirty nine, g E showed off a solar power concept 0:04:04.400 --> 0:04:08.240 called the sun Motor at the nineteen nine World's Fair. 0:04:08.760 --> 0:04:11.920 The following year, also for the World's Fair, g E 0:04:12.200 --> 0:04:16.839 showed off a lightning generator which created enormous powerful sparks 0:04:16.920 --> 0:04:21.320 between giant pillars, and in nineteen forty one, the company 0:04:21.360 --> 0:04:25.040 had been instrumental in building the first US jet engine, 0:04:25.120 --> 0:04:31.080 called the one A. Paul got to work on magnetron's originally, 0:04:31.320 --> 0:04:34.800 and I mentioned magnetrons in recent episodes on Alfred Lee 0:04:34.880 --> 0:04:39.839 Loomis and the Loran System. A magnetron is essentially a 0:04:39.920 --> 0:04:44.520 microwave generator. Inside a magnetron is a cathode. This is 0:04:44.560 --> 0:04:46.680 where our electrons come from. You can think of it 0:04:46.720 --> 0:04:50.600 as an electron generator. And when you heat up this cathode, 0:04:50.960 --> 0:04:53.800 you pour energy into it and it begins to boil 0:04:54.000 --> 0:04:58.159 off or release electrons. Now, what you're actually doing is 0:04:58.160 --> 0:05:01.720 boosting the energy level of re electrons in the cathode 0:05:02.160 --> 0:05:06.240 and Finally they get enough energy to go out and 0:05:06.279 --> 0:05:10.120 find adventure in the great wide somewhere, assuming there's a 0:05:10.160 --> 0:05:13.680 positively charged material nearby for them to go to. So 0:05:13.720 --> 0:05:17.039 surrounding the cathode is an anode in the shape of 0:05:17.080 --> 0:05:20.480 a ring, and this ring has some sort of notches 0:05:20.600 --> 0:05:25.839 or or or alcoves carved into it. These are the 0:05:26.000 --> 0:05:30.200 so called cavities of a cavity magnetron. They're sometimes called 0:05:30.400 --> 0:05:33.320 resonant cavities. Now that's going to be important in just 0:05:33.400 --> 0:05:37.039 a second. So imagine the cathode is a stick, and 0:05:37.080 --> 0:05:40.280 there's a ring surrounding the stick, and the ring has 0:05:40.320 --> 0:05:44.280 these little alcoves or cavities inside of it. The anode 0:05:44.440 --> 0:05:49.200 has a lack of electrons, giving it a net positive charge. Now, 0:05:49.320 --> 0:05:52.919 if there were nothing else to a magnetron, if it 0:05:53.000 --> 0:05:55.360 was just the cathode and the anode, and you were 0:05:55.400 --> 0:05:57.359 to turn it on and start to heat up the 0:05:57.400 --> 0:06:00.560 cathode and boil off those electrons, the all actrons would 0:06:00.600 --> 0:06:02.760 just zip on over to the anode once they had 0:06:02.880 --> 0:06:06.039 enough energy to do so. But there's a bit more 0:06:06.160 --> 0:06:09.599 to a magnetron than that. A final piece of the 0:06:09.640 --> 0:06:13.520 magnetron is a magnet underneath the anode. This creates a 0:06:13.560 --> 0:06:17.960 magnetic field that is parallel to the cathode. So when 0:06:18.000 --> 0:06:20.960 you heat up that cathode, the electrons are moving through 0:06:21.000 --> 0:06:24.400 both an electrical field and a magnetic field. As the 0:06:24.400 --> 0:06:28.520 electrons zoom past the cavities in the anode, these little alcoves, 0:06:28.640 --> 0:06:32.520 they cause the cavities to resonate, and this resonation creates 0:06:32.720 --> 0:06:36.719 microwave radiation. The wavelength of the microwave is dependent upon 0:06:36.839 --> 0:06:40.400 the size and shape of the cavity. One source I 0:06:40.440 --> 0:06:43.919 looked at while researching this likened the resonating cavities to 0:06:44.000 --> 0:06:47.640 a musical instrument that you blow across. So, since I'm 0:06:47.720 --> 0:06:50.640 from the Deep South in the United States, I'm going 0:06:50.680 --> 0:06:55.640 to use a wonderful musical instrument that is beloved here 0:06:55.680 --> 0:07:00.240 in my home state, a good old jug. When you 0:07:00.240 --> 0:07:03.000 blow across the top of a jug, it produces a 0:07:03.040 --> 0:07:06.839 note that who, well, there's a resonating chamber here in 0:07:06.880 --> 0:07:09.359 the form of the jug. The same thing is true 0:07:09.520 --> 0:07:13.040 inside this anode. The cavities and the magnetron behave in 0:07:13.080 --> 0:07:16.760 a similar way. As the electrons zoom pass the opening 0:07:16.800 --> 0:07:20.000 to the cavities, they pass some of their energy along 0:07:20.120 --> 0:07:25.240 which resonates and generates microwave radiation instead of sound. Magnetrons 0:07:25.320 --> 0:07:28.360 also have something called a wave guide, which, as the 0:07:28.440 --> 0:07:32.640 name suggests, is the method for guiding the microwaves to 0:07:32.720 --> 0:07:36.120 emit outward from the magnetron. Then you can use the 0:07:36.160 --> 0:07:39.360 microwaves for whatever purpose you had intended, such as to 0:07:39.400 --> 0:07:43.440 create a maser sort of the microwave predecessor to the laser, 0:07:44.040 --> 0:07:46.680 or you could do it to create a microwave oven, 0:07:47.040 --> 0:07:50.560 or a power the power source, or rather the microwave 0:07:50.600 --> 0:07:54.520 source for radar equipment. Hall's work on magnetrons will become 0:07:54.520 --> 0:07:57.760 a major contributor to the development of the microwave oven 0:07:58.040 --> 0:08:00.760 at g E, which was led by another guy named 0:08:00.840 --> 0:08:03.320 Rudy Den. And I've talked a little bit about that too, 0:08:03.360 --> 0:08:09.160 About the almost accidental discovery of how a microwave source 0:08:09.200 --> 0:08:12.640 could be used as an oven. I believe it involved 0:08:12.720 --> 0:08:15.920 the melting of a chocolate bar in someone's pants pocket. 0:08:16.440 --> 0:08:21.080 Such is the majesty of electrical engineering. I have more 0:08:21.120 --> 0:08:23.000 to say about Dr Hall in just a second, but 0:08:23.080 --> 0:08:26.040 first let's take a quick break to thank our sponsor. 0:08:33.360 --> 0:08:37.320 Hall also got to work on crystal diodes. Diodes are 0:08:37.360 --> 0:08:40.640 an important element in circuitry as they allow electricity to 0:08:40.640 --> 0:08:43.800 flow only in one direction, so it's sort of like 0:08:43.920 --> 0:08:48.160 a traffic keeping mechanism for electricity. Diodes are a simple 0:08:48.280 --> 0:08:53.439 kind of semiconductor. Semiconductors, as the name suggests, can act 0:08:53.520 --> 0:08:58.600 as conductors under certain circumstances and insulators and other circumstances. 0:08:58.960 --> 0:09:02.400 And these semiconductor is consisted of different materials that have 0:09:02.600 --> 0:09:08.400 specific properties. And N type material has extra negatively charged 0:09:08.480 --> 0:09:14.160 particles or electrons. A P type material has positive charge, 0:09:14.440 --> 0:09:16.520 so it would have what people would refer to as 0:09:16.600 --> 0:09:22.839 electron holes. It has a positive acceptance for electrons. By 0:09:22.880 --> 0:09:26.880 sandwiching these two materials together, you can create a semiconductor, 0:09:27.320 --> 0:09:30.400 a material that will conduct electricity along one direction but 0:09:30.520 --> 0:09:33.000 stop it from the other. This would be a diode. 0:09:33.400 --> 0:09:36.360 So how does this work? Why does electricity go one 0:09:36.360 --> 0:09:38.600 way but not the other way? Well, imagine you have 0:09:38.640 --> 0:09:43.400 a battery hooked up to this semiconductor diode, and the 0:09:43.400 --> 0:09:46.480 battery has a negative side and a positive side, as 0:09:46.520 --> 0:09:50.720 does the diode. The battery serves up direct current, meaning 0:09:50.760 --> 0:09:53.920 that the electricity will only flow through this direct path 0:09:54.040 --> 0:09:56.760 from the negative side to the positive side. If you're 0:09:56.760 --> 0:10:00.760 talking about electrons. We're not talking about the crazy way 0:10:00.760 --> 0:10:04.360 of saying positive to negative, which is the way Benjamin 0:10:04.360 --> 0:10:06.680 Franklin would have wanted it. We're just gonna talk about 0:10:06.720 --> 0:10:09.480 electrons here. If you hook the negative end of the 0:10:09.480 --> 0:10:12.840 battery up to the N type side of the semiconductor, 0:10:13.320 --> 0:10:16.960 the electrons flowing from the battery essentially push other electrons 0:10:17.000 --> 0:10:19.199 across to the P type material on the other side 0:10:19.240 --> 0:10:22.040 of the semiconductor and comes through the other side to 0:10:22.080 --> 0:10:26.280 the positive contact on the battery, and you have the 0:10:26.280 --> 0:10:29.400 flow of electricity. It just continues from negative to positive. 0:10:29.640 --> 0:10:31.960 The positive holes in the P type are attracted to 0:10:31.960 --> 0:10:34.840 the negatively charged particles in the N type, and current 0:10:34.880 --> 0:10:37.640 flows in this direction. But if you were to flip 0:10:37.679 --> 0:10:40.560 the battery around so that the negative side of the 0:10:40.559 --> 0:10:44.160 battery connected to the P type side of the semiconductor, 0:10:44.559 --> 0:10:47.400 the incoming electrons from the battery would just end up 0:10:47.400 --> 0:10:49.920 hooking up with these positive holes on the P type side. 0:10:50.240 --> 0:10:55.960 No electricity would flow. The two charges would separate within 0:10:56.000 --> 0:10:58.520 the semiconductor material, and so you wouldn't be able to 0:10:58.559 --> 0:11:00.640 pass a current in between it. It would act as 0:11:00.640 --> 0:11:04.720 an insulator. Hall worked on technologies like these for about 0:11:04.760 --> 0:11:07.920 three or four years before being urged by his colleagues 0:11:07.960 --> 0:11:11.120 to continue his studies and earn a pH d. And 0:11:11.160 --> 0:11:14.480 so Hall returned to cal Tech and got back to work. 0:11:14.880 --> 0:11:19.160 He graduated in night with a doctorate in nuclear physics 0:11:19.480 --> 0:11:22.000 and then returned to ge just in time to hear 0:11:22.000 --> 0:11:25.640 about a new discovery coming out of Bell Labs. This 0:11:25.760 --> 0:11:29.160 was called the transistor, and it would change Hall's life. 0:11:29.760 --> 0:11:33.440 The transistor was a huge breakthrough and engineering. It could 0:11:33.440 --> 0:11:37.120 perform as a switch or as an amplifier. And as 0:11:37.120 --> 0:11:40.640 an amplifier, a transistor takes in a weak electric current 0:11:40.760 --> 0:11:44.680 in the input and produces a stronger electric current in 0:11:44.760 --> 0:11:49.240 the output. As a switch, the transistor can create a 0:11:49.360 --> 0:11:52.360 strong electric current to flow through part of the transistor 0:11:52.679 --> 0:11:55.240 as a weak electric current flows in from another part, 0:11:55.440 --> 0:11:58.640 so it switches on that stronger electric current. If you 0:11:58.760 --> 0:12:01.360 turn off the weak electric current, the strong electric current 0:12:01.400 --> 0:12:04.320 also turns off. Now, in the previous section I mentioned 0:12:04.320 --> 0:12:07.160 at a very high level how a diode works by 0:12:07.200 --> 0:12:10.280 pairing in type and P type material in a simple way. 0:12:10.760 --> 0:12:13.800 A transistor is similar, except you can think of it 0:12:13.920 --> 0:12:18.000 as even more like a sandwich. And there are different types. 0:12:18.040 --> 0:12:21.960 But let's take an N P N junction transistor as 0:12:22.000 --> 0:12:25.679 an example. So imagine you've got a bit of P 0:12:25.920 --> 0:12:29.720 type material, meaning positively charged, so it's got the electron 0:12:29.800 --> 0:12:32.959 holes in it, and it's sandwiched between two different N 0:12:33.080 --> 0:12:36.360 type material sections. So these are areas that have a 0:12:37.080 --> 0:12:40.199 negative charge on either side. So the middle is your 0:12:40.200 --> 0:12:42.760 P type. On left and right you've got your N type. 0:12:43.360 --> 0:12:45.240 Uh So in a circuit you would say it's N 0:12:45.240 --> 0:12:48.200 type P type N type. On one N type end 0:12:48.280 --> 0:12:50.839 you have the collector side. On the other N type 0:12:50.880 --> 0:12:53.720 end you have the emitter side, and connected to the 0:12:53.760 --> 0:12:57.200 P type material, you have the base, and it's all 0:12:57.280 --> 0:13:00.199 about that base. Now, if you were to a ply 0:13:00.240 --> 0:13:03.600 of voltage between the base and the emitter, it would 0:13:03.600 --> 0:13:07.760 cause current to flow from the base to the emitter. This, 0:13:07.800 --> 0:13:11.480 in turn would allow a stronger current to flow from 0:13:11.520 --> 0:13:15.360 the collector to the emitter. The transistor would take on 0:13:15.480 --> 0:13:19.040 the rolls of another older piece of technology, the vacuum tube. 0:13:19.400 --> 0:13:21.840 And I've talked a lot about vacuum tubes in recent episodes, 0:13:21.880 --> 0:13:23.960 so you can listen to those and learn more about them. 0:13:24.000 --> 0:13:26.479 But the thing to remember here is that the transistor 0:13:26.480 --> 0:13:29.160 had the potential to take the place of vacuum tubes 0:13:29.520 --> 0:13:33.079 and drastically reduce the size of electronics, not to mention 0:13:33.120 --> 0:13:35.480 cut back on the amount of heat they would produce. 0:13:36.320 --> 0:13:39.520 Hall began to look into transistors over at GE and 0:13:39.559 --> 0:13:43.920 began to experiment with creating high purity germanium through a 0:13:43.960 --> 0:13:49.280 process called fractional crystallization. Hall found that by freezing germanium 0:13:49.280 --> 0:13:53.040 into a crystal would push most of the impurities away 0:13:53.120 --> 0:13:56.920 from the crystalline structure that formed inside the solid germanium, 0:13:56.960 --> 0:14:00.599 and by doing this slowly across a sample of germ manium, 0:14:00.640 --> 0:14:04.200 you could effectively push the impurities onto one end, and 0:14:04.360 --> 0:14:07.679 thus you would have a doped end of your germanium 0:14:07.720 --> 0:14:11.880 crystal while you have high quality germanium. But this process 0:14:11.920 --> 0:14:14.800 was pretty slow. Hall found that his process would create 0:14:14.800 --> 0:14:17.800 germanium that was a crystal diode, so you'd have one 0:14:17.920 --> 0:14:21.120 end that would act as a P type material and 0:14:21.160 --> 0:14:23.200 the other end of the same crystal would act as 0:14:23.200 --> 0:14:26.680 an end type material. And he used arsenic to dope 0:14:26.760 --> 0:14:30.520 the germanium, meaning he was introducing an impurity on purpose 0:14:30.840 --> 0:14:33.040 to alter the structure of the material to make it 0:14:33.120 --> 0:14:37.440 an effective semiconductor. He also found out that this introduced 0:14:37.480 --> 0:14:40.560 boron to the material, which he found very interesting. His 0:14:40.640 --> 0:14:44.440 work would later become really important for power plants because 0:14:44.480 --> 0:14:46.840 the materials he was working with ended up being able 0:14:46.880 --> 0:14:50.240 to handle tremendous voltages, so they became very important in 0:14:50.320 --> 0:14:54.440 g S work with electricity generation. Hall's work with germanium 0:14:54.520 --> 0:14:56.960 lead him to develop technologies that were useful in the 0:14:57.000 --> 0:15:00.280 detection of gamma rays, something that was important both in 0:15:00.400 --> 0:15:05.600 nuclear physics and cosmology. Gamma rays are type of nuclear radiation. 0:15:05.760 --> 0:15:09.560 It's electromagnetic radiation that typically comes from the radioactive decay 0:15:09.720 --> 0:15:12.800 of nuclei, and it is made up of photons, with 0:15:12.840 --> 0:15:17.120 the highest observed photonic energy we've seen so far. They 0:15:17.360 --> 0:15:21.400 also are an ionizing type of radiation, meaning the energy 0:15:21.440 --> 0:15:24.360 from gamma rays can strip away electrons from other atoms. 0:15:24.680 --> 0:15:28.880 Ionizing radiation is potentially dangerous. It can cause cellular damage 0:15:28.920 --> 0:15:33.720 and potentially genetic damage to an organism subjected to them, 0:15:33.880 --> 0:15:37.760 not to mention increase the probability of cancer, so they're 0:15:37.840 --> 0:15:40.720 dangerous things. It's not as dangerous as alpha or beta waves, 0:15:40.760 --> 0:15:43.720 generally speaking, just because they didn't to pass right through 0:15:43.800 --> 0:15:47.560 stuff as opposed to getting absorbed. Really one area of 0:15:47.560 --> 0:15:50.760 focus Hall dedicated himself too. In the early nineteen fifties, 0:15:50.840 --> 0:15:55.040 was working on a semiconductor device capable of producing light, 0:15:55.600 --> 0:15:59.960 a light emitting diode, in other words. A decade later, 0:16:00.000 --> 0:16:03.280 a colleague suggested to Hall that he used semiconductors to 0:16:03.360 --> 0:16:07.440 make a laser. Now in the nineteen fifties, Charles hard 0:16:07.520 --> 0:16:11.680 Towns showed how through the use of stimulated missions of radiation, 0:16:12.520 --> 0:16:15.920 he could create a maser sort of the microwave variant 0:16:16.040 --> 0:16:19.240 of a laser. At In nineteen fifty nine, Gordon Gould 0:16:19.240 --> 0:16:21.800 published a paper suggesting it would be possible to create 0:16:21.880 --> 0:16:25.960 light amplification by stimulated emission of radiation or a laser. 0:16:26.440 --> 0:16:28.600 The basic idea is that you have to have some 0:16:28.640 --> 0:16:32.640 sort of lasing medium. We typically would use a gas 0:16:32.800 --> 0:16:36.240 or a crystal. Something like a ruby laser actually uses 0:16:36.320 --> 0:16:39.240 ruby crystals to do this. This is a material that 0:16:39.280 --> 0:16:43.400 will absorb energy, typically either light or heat than As 0:16:43.440 --> 0:16:46.160 it does so, the electrons and the material are excited 0:16:46.200 --> 0:16:50.480 to higher energy states than their normal rest state. Now, 0:16:50.520 --> 0:16:54.400 this cannot continue indefinitely, and eventually the electrons will decay 0:16:54.520 --> 0:16:58.920 to a lower energy state, and those electrons, when they 0:16:58.920 --> 0:17:01.880 returned to their nor will energy state have to get 0:17:01.960 --> 0:17:04.800 rid of that excess energy. You can't just pump energy 0:17:04.840 --> 0:17:08.080 into electron, push it to a higher energy state and 0:17:08.080 --> 0:17:10.320 then it comes back down without getting rid of that 0:17:10.440 --> 0:17:14.000 energy and has to admit it somehow. So they shed 0:17:14.040 --> 0:17:17.640 that excess energy in the form of photons or particles 0:17:17.640 --> 0:17:21.199 of light. Now those photons are not necessarily within the 0:17:21.359 --> 0:17:25.760 visible spectrum of light. You can create stuff like infrared lasers, 0:17:25.760 --> 0:17:28.879 for example, which are invisible to the naked eye. But 0:17:28.960 --> 0:17:32.240 the full technical details of lasers get way more complicated 0:17:32.240 --> 0:17:35.439 than this, But it's a pretty good basic explanation of 0:17:35.480 --> 0:17:38.400 what's going on and what Dr Hall was trying to achieve. 0:17:38.680 --> 0:17:41.520 Only he was trying to do it with semiconductors, which 0:17:41.560 --> 0:17:44.320 no one had done yet to that point. All the 0:17:44.359 --> 0:17:47.080 ones that had been used had used flash arc lamps 0:17:47.119 --> 0:17:50.800 and other big pieces of equipment, but not semiconductors. So 0:17:50.840 --> 0:17:53.200 how did he do it well. I'll talk a little 0:17:53.200 --> 0:17:55.640 bit about that in just a second, but first let's 0:17:55.640 --> 0:18:05.920 take another quick break to thank our sponsor. Now, the 0:18:05.960 --> 0:18:09.159 first functioning laser debut in nineteen sixty and was the 0:18:09.160 --> 0:18:13.840 work of Theodore H. Meiman at Hughes Research Laboratories, but 0:18:13.960 --> 0:18:17.800 early lasers did not use semiconductors. Hall would be pioneering 0:18:17.960 --> 0:18:22.000 new ground, and he himself was skeptical at first. He 0:18:22.080 --> 0:18:26.919 felt that optical efficiency of diodes was not nearly efficient 0:18:27.520 --> 0:18:31.199 or powerful enough. But Hall was intrigued and began to 0:18:31.240 --> 0:18:35.119 explore the possibilities, and as he researched lasers, he began 0:18:35.160 --> 0:18:39.359 to theorize away he might actually make a semiconductor injection 0:18:39.440 --> 0:18:43.960 based laser. He would need to create a gallium arsenid 0:18:44.080 --> 0:18:48.320 diode and have special mirrors to create this actual laser. 0:18:48.359 --> 0:18:50.840 And he went to his bosses and he had this request. 0:18:50.840 --> 0:18:53.359 He said, hey, can I make a team and work 0:18:53.400 --> 0:18:57.720 on this project. He had absolutely no practical application for lasers. 0:18:57.760 --> 0:18:59.960 He didn't think of anything that they could actually use 0:19:00.000 --> 0:19:02.399 whose lasers for. But he thought it would be quote 0:19:02.880 --> 0:19:06.159 fun to work on end quote, so he pitched it 0:19:06.320 --> 0:19:08.960 and his bosses were intrigued, so they signed off on 0:19:09.000 --> 0:19:11.439 his pet project and he got to work. After some 0:19:11.560 --> 0:19:16.000 intense research and development, Hall's small team of researchers produced 0:19:16.040 --> 0:19:20.120 a working laser using semiconductors, and they ran numerous tests. 0:19:20.160 --> 0:19:23.159 They refined their design, built a better model, and they 0:19:23.200 --> 0:19:25.760 wrote up their research. They published their work in a 0:19:25.760 --> 0:19:30.359 scientific journal. Meanwhile, at pretty much the same time, IBM 0:19:30.400 --> 0:19:34.000 announced it had created something that was almost but not 0:19:34.160 --> 0:19:37.840 quite a working laser. However, they were very close to 0:19:37.880 --> 0:19:41.320 having it ready to go, and in an unusual move, 0:19:41.480 --> 0:19:44.439 both IBM and Hall's team would be awarded a patent 0:19:44.600 --> 0:19:49.600 for the technology. Hall's friend Nick holland Niak built off 0:19:49.720 --> 0:19:54.680 of Hall's work, using diodes made from gallium arsenide phosphied 0:19:54.800 --> 0:19:57.560 in an attempt to create a light emitting diode that 0:19:57.600 --> 0:20:01.360 could emit light in the visible spectrum. So the laser 0:20:01.600 --> 0:20:04.399 that Hall had created was an infrared laser, it was 0:20:04.440 --> 0:20:06.600 not something that was visible, and he would make the 0:20:06.680 --> 0:20:10.240 first visible laser just a short while after. Hall's team 0:20:10.400 --> 0:20:15.440 demonstrated that semiconductor lasers were possible, but no one at 0:20:15.480 --> 0:20:18.560 this point knew what they would ever use lasers for, 0:20:18.920 --> 0:20:21.479 and at that time it was more about overcoming the 0:20:21.520 --> 0:20:26.240 engineering challenge and conducting various experiments to see what was possible. 0:20:26.720 --> 0:20:30.280 The lasers Hall made were primitive by today's standards. They 0:20:30.280 --> 0:20:34.200 would only operate in the temperature of liquid air, which 0:20:34.200 --> 0:20:37.040 means you had to cool them down to below negative 0:20:37.160 --> 0:20:41.960 one four point thirty five degrees celsius, the boiling point 0:20:42.280 --> 0:20:46.600 that's in between liquid nitrogen and liquid oxygen. That wouldn't 0:20:46.640 --> 0:20:50.399 make a very practical laser for most applications because imagine 0:20:50.640 --> 0:20:52.520 that you would have to carry around a laser pointer 0:20:52.600 --> 0:20:55.000 that must always be connected to a cooling device that 0:20:55.160 --> 0:20:57.760 kept everything at a ridiculously low temperature. It would be 0:20:57.880 --> 0:21:02.439 dangerous and inconvenient. In addition, Hall's team created a laser 0:21:02.600 --> 0:21:05.359 that worked in pulses. There was no real way to 0:21:05.400 --> 0:21:09.480 create a continuous laser using their approach. The team had 0:21:09.560 --> 0:21:13.040 made an enormous achievement, but would require the work of 0:21:13.160 --> 0:21:17.919 dozens more scientists and engineers to refine and improve designs 0:21:18.240 --> 0:21:21.080 to make lasers something that could find a use outside 0:21:21.119 --> 0:21:25.360 of laboratory demonstrations. As it turned out, the laser would 0:21:25.400 --> 0:21:28.960 have numerous applications. This was something the team didn't have 0:21:29.040 --> 0:21:31.600 to worry about while they were working on developing the laser, 0:21:32.040 --> 0:21:35.200 but one of the most important applications was in the 0:21:35.240 --> 0:21:39.200 field of fiber optics. A fiber optic cable is a 0:21:39.240 --> 0:21:42.960 conduit for light. It is constructed in such a way 0:21:43.359 --> 0:21:46.560 as to guide light down a pathway made out of 0:21:46.560 --> 0:21:49.960 glass without losing too much in the process, but it 0:21:49.960 --> 0:21:53.760 requires a light source with a very narrow focus. Lasers 0:21:53.760 --> 0:21:57.240 were the obvious solution to that problem. In addition, it 0:21:57.280 --> 0:22:02.480 wasn't difficult to insert patterns into laser light to represent information. 0:22:03.000 --> 0:22:06.520 This modulation made it possible to send information down a 0:22:06.560 --> 0:22:09.960 fiber optic line. Basically, the way it works is you 0:22:10.000 --> 0:22:12.800 have a computer system on one end. It takes data 0:22:13.080 --> 0:22:15.400 and then encodes that information in a way that can 0:22:15.440 --> 0:22:19.639 be transmitted via laser light down a fiber optic cable, 0:22:20.080 --> 0:22:23.480 so that data ends up modifying the laser light in 0:22:23.520 --> 0:22:26.560 some way. It might be in phase, it might be impulses, 0:22:26.600 --> 0:22:29.119 it might be lots of different ways, and the laser 0:22:29.240 --> 0:22:32.560 light then zaps down this fiber optic cable. It travels 0:22:32.600 --> 0:22:35.240 at the speed of light to its destination some other 0:22:35.240 --> 0:22:40.520 computers somewhere else, and a receiver ends up detecting the 0:22:40.560 --> 0:22:44.960 incoming laser message through the fiber optics. A decoder takes 0:22:45.000 --> 0:22:48.119 that signal and transforms it back into useful information that 0:22:48.160 --> 0:22:52.680 the computer can actually process. Haul's semiconductor laser made all 0:22:52.720 --> 0:22:55.119 of that possible. It's also the type of laser you 0:22:55.200 --> 0:22:58.879 might find in a CD layer, which my producer Tari 0:22:58.920 --> 0:23:01.560 would be very happy to hear about and her love 0:23:01.560 --> 0:23:05.679 of CDs. Another widespread application of semiconductor lasers is the 0:23:05.800 --> 0:23:09.520 barcode scanner. That's something we see in our day to 0:23:09.600 --> 0:23:12.440 day lives. Barcodes are great if you need a way 0:23:12.480 --> 0:23:15.880 to keep accurate inventory management. You just slap a barcode 0:23:15.920 --> 0:23:18.439 unique to the type of material you're working with, and 0:23:18.480 --> 0:23:22.080 you scan everything into a system to establish your inventory, 0:23:22.160 --> 0:23:24.280 and then you can scan it again whenever you need 0:23:24.320 --> 0:23:28.000 to give it away, to use something or to sell something. 0:23:28.240 --> 0:23:30.840 So let's go with a grocery store example, because I 0:23:30.880 --> 0:23:33.199 think it's something that we can all identify with. You 0:23:33.240 --> 0:23:36.159 walk it to your grocery store and you go in 0:23:36.200 --> 0:23:38.840 there to buy something real tasty. Let's say it's um 0:23:39.080 --> 0:23:42.040 spicy salsa. So you pick up a jar of your 0:23:42.040 --> 0:23:45.080 favorite brand. And by the way, and I'm being serious here, 0:23:46.080 --> 0:23:49.200 if you have a favorite brand of salsa, you need 0:23:49.240 --> 0:23:51.119 to tell me about it, because I am always on 0:23:51.160 --> 0:23:54.760 the lookout for a really good, flavorful spicy salsa. The 0:23:54.800 --> 0:23:57.120 hotter the better, but I wanted to taste good. Anyway, 0:23:57.160 --> 0:23:59.400 back to this example, more important stuff to talk about. 0:23:59.760 --> 0:24:02.720 You bring your jar of tasty salsa up to the 0:24:02.720 --> 0:24:04.960 front of the store. Maybe you go through the self 0:24:05.040 --> 0:24:07.359 checkout lane, maybe you get in lines so that a 0:24:07.440 --> 0:24:10.440 cashier does the checkout process, but either way you soon 0:24:10.520 --> 0:24:13.240 reach the point where the jar is going to be scanned. 0:24:13.680 --> 0:24:18.320 A barcode scanner uses light to shine onto a barcode, 0:24:18.320 --> 0:24:22.719