Get in tech with technology with tech Stuff from stuff works dot com. Hey there, and welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm an executive producer at how Stuff Works and I love all things tech. And on Christmas Day nineteen nineteen, Dr Robert N. Hall was born in New Haven, Connecticut. He would pass away on November seven, two thousand sixteen, at the age of nineties six.
The New York Times would publish an obituary about Dr Hall on May tenth, two thousand eighteen, with the title Robert N. Hall, ninety six, whose inventions are everywhere? Is dead? What's so remarkable about this gentleman that necessitated an obituary in the New York Times nearly two years after he actually passed away? And I the late obituary anyway, Well, we're gonna learn about Dr Robert INN. Hall and his
numerous inventions. Hall grew up in Connecticut, and when he was a boy, his uncle took him to a technical fair, kind of a science and engineering festival. His uncle considered himself something of an inventor, and he wanted to encourage Robert to explore topics of science and technology. And according to an interview that Dr Hall gave in two thousand four, he said, quote, he took me to a technology fair when I was a small boy in New Haven, Connecticut,
and there were a lot of electrical exhibits. Bouncing steel ball bearings and tin can motors were spinning on a flat table stroboscopes. He got my attention. It seems like these were fascinating little things, and I would like to know how they worked. And he tried to explain them to me, and he showed me where to find books in the library. Later on, when I went to high school, my mom let me have a little laboratory in the bedroom, and I said, up a lot of experiments and see
if I can duplicate a lot of these things. End quote. Hall continued his experiments and pursued his interest in the sciences. He initially focused on astronomy, which is a bit of a pun because he actually took it upon himself to build his own eight inch telescope, including grinding the mirrors himself. While in high school, he met with a recruiter for
cal Tech or the California Technical Institute. This led to Hall taking some entrance exams for the school and he must have performed pretty well on those tests because he ended up with a scholarship to attend cal Tech. Hall studied science and engineering at school for three years, at which point he ran out of money and he had to take a year off to earn more. To finish out his studies. He got a job at lockeed Aircraft as a test engineer. This was just before the United
States would be pulled into World War Two. After a year of working at Lockheed, he returned to cal Tech and finished out his studies, earning a degree in physics. Immediately upon graduation, he was recruited by GE that is, General Electric to come and work for them as a test engineer in Schenectady, New York. General Electric was the company that grew out of the merger of Thomas Edison's General Electric Company and the Thomas Houston Electric Company of Lynn, Massachusetts.
Both Thomas Edison and Charles Coffin, who were the leaders of the two companies, had made numerous acquisitions in the late nineteenth century and grown their respective companies considerably. General Electric became a sizeable conglomerate the day it formed through this merger in the late eighteen nineties. In nineteen hundred, GE created its own industrial research laboratory. By the time Hall went to work for the company in nineteen forty two,
GE was known for introducing several technological innovations. In nineteen thirty nine, g E showed off a solar power concept called the sun Motor at the nineteen nine World's Fair.
The following year, also for the World's Fair, g E showed off a lightning generator which created enormous powerful sparks between giant pillars, and in nineteen forty one, the company had been instrumental in building the first US jet engine, called the one A. Paul got to work on magnetron's originally, and I mentioned magnetrons in recent episodes on Alfred Lee Loomis and the Loran System. A magnetron is essentially a microwave generator. Inside a magnetron is a cathode. This is
where our electrons come from. You can think of it as an electron generator. And when you heat up this cathode, you pour energy into it and it begins to boil off or release electrons. Now, what you're actually doing is boosting the energy level of re electrons in the cathode and Finally they get enough energy to go out and find adventure in the great wide somewhere, assuming there's a
positively charged material nearby for them to go to. So surrounding the cathode is an anode in the shape of a ring, and this ring has some sort of notches or or or alcoves carved into it. These are the so called cavities of a cavity magnetron. They're sometimes called resonant cavities. Now that's going to be important in just a second. So imagine the cathode is a stick, and there's a ring surrounding the stick, and the ring has these little alcoves or cavities inside of it. The anode
has a lack of electrons, giving it a net positive charge. Now, if there were nothing else to a magnetron, if it was just the cathode and the anode, and you were to turn it on and start to heat up the cathode and boil off those electrons, the all actrons would just zip on over to the anode once they had enough energy to do so. But there's a bit more to a magnetron than that. A final piece of the magnetron is a magnet underneath the anode. This creates a
magnetic field that is parallel to the cathode. So when you heat up that cathode, the electrons are moving through both an electrical field and a magnetic field. As the electrons zoom past the cavities in the anode, these little alcoves, they cause the cavities to resonate, and this resonation creates microwave radiation. The wavelength of the microwave is dependent upon the size and shape of the cavity. One source I looked at while researching this likened the resonating cavities to
a musical instrument that you blow across. So, since I'm from the Deep South in the United States, I'm going to use a wonderful musical instrument that is beloved here in my home state, a good old jug. When you blow across the top of a jug, it produces a note that who, well, there's a resonating chamber here in the form of the jug. The same thing is true inside this anode. The cavities and the magnetron behave in
a similar way. As the electrons zoom pass the opening to the cavities, they pass some of their energy along which resonates and generates microwave radiation instead of sound. Magnetrons also have something called a wave guide, which, as the name suggests, is the method for guiding the microwaves to
emit outward from the magnetron. Then you can use the microwaves for whatever purpose you had intended, such as to create a maser sort of the microwave predecessor to the laser, or you could do it to create a microwave oven, or a power the power source, or rather the microwave source for radar equipment. Hall's work on magnetrons will become a major contributor to the development of the microwave oven at g E, which was led by another guy named
Rudy Den. And I've talked a little bit about that too, About the almost accidental discovery of how a microwave source could be used as an oven. I believe it involved the melting of a chocolate bar in someone's pants pocket. Such is the majesty of electrical engineering. I have more to say about Dr Hall in just a second, but first let's take a quick break to thank our sponsor.
Hall also got to work on crystal diodes. Diodes are an important element in circuitry as they allow electricity to flow only in one direction, so it's sort of like a traffic keeping mechanism for electricity. Diodes are a simple kind of semiconductor. Semiconductors, as the name suggests, can act as conductors under certain circumstances and insulators and other circumstances. And these semiconductor is consisted of different materials that have
specific properties. And N type material has extra negatively charged particles or electrons. A P type material has positive charge, so it would have what people would refer to as electron holes. It has a positive acceptance for electrons. By sandwiching these two materials together, you can create a semiconductor, a material that will conduct electricity along one direction but stop it from the other. This would be a diode. So how does this work? Why does electricity go one
way but not the other way? Well, imagine you have a battery hooked up to this semiconductor diode, and the battery has a negative side and a positive side, as does the diode. The battery serves up direct current, meaning that the electricity will only flow through this direct path from the negative side to the positive side. If you're talking about electrons. We're not talking about the crazy way of saying positive to negative, which is the way Benjamin
Franklin would have wanted it. We're just gonna talk about electrons here. If you hook the negative end of the battery up to the N type side of the semiconductor, the electrons flowing from the battery essentially push other electrons across to the P type material on the other side of the semiconductor and comes through the other side to the positive contact on the battery, and you have the flow of electricity. It just continues from negative to positive.
The positive holes in the P type are attracted to the negatively charged particles in the N type, and current flows in this direction. But if you were to flip the battery around so that the negative side of the battery connected to the P type side of the semiconductor, the incoming electrons from the battery would just end up hooking up with these positive holes on the P type side.
No electricity would flow. The two charges would separate within the semiconductor material, and so you wouldn't be able to pass a current in between it. It would act as an insulator. Hall worked on technologies like these for about three or four years before being urged by his colleagues to continue his studies and earn a pH d. And so Hall returned to cal Tech and got back to work. He graduated in night with a doctorate in nuclear physics and then returned to ge just in time to hear
about a new discovery coming out of Bell Labs. This was called the transistor, and it would change Hall's life. The transistor was a huge breakthrough and engineering. It could perform as a switch or as an amplifier. And as an amplifier, a transistor takes in a weak electric current in the input and produces a stronger electric current in
the output. As a switch, the transistor can create a strong electric current to flow through part of the transistor as a weak electric current flows in from another part, so it switches on that stronger electric current. If you turn off the weak electric current, the strong electric current also turns off. Now, in the previous section I mentioned at a very high level how a diode works by pairing in type and P type material in a simple way. A transistor is similar, except you can think of it
as even more like a sandwich. And there are different types. But let's take an N P N junction transistor as an example. So imagine you've got a bit of P type material, meaning positively charged, so it's got the electron holes in it, and it's sandwiched between two different N type material sections. So these are areas that have a negative charge on either side. So the middle is your P type. On left and right you've got your N type. Uh So in a circuit you would say it's N
type P type N type. On one N type end you have the collector side. On the other N type end you have the emitter side, and connected to the P type material, you have the base, and it's all about that base. Now, if you were to a ply of voltage between the base and the emitter, it would cause current to flow from the base to the emitter. This, in turn would allow a stronger current to flow from
the collector to the emitter. The transistor would take on the rolls of another older piece of technology, the vacuum tube. And I've talked a lot about vacuum tubes in recent episodes, so you can listen to those and learn more about them. But the thing to remember here is that the transistor had the potential to take the place of vacuum tubes and drastically reduce the size of electronics, not to mention cut back on the amount of heat they would produce.
Hall began to look into transistors over at GE and began to experiment with creating high purity germanium through a process called fractional crystallization. Hall found that by freezing germanium into a crystal would push most of the impurities away from the crystalline structure that formed inside the solid germanium, and by doing this slowly across a sample of germ manium, you could effectively push the impurities onto one end, and thus you would have a doped end of your germanium
crystal while you have high quality germanium. But this process was pretty slow. Hall found that his process would create germanium that was a crystal diode, so you'd have one end that would act as a P type material and the other end of the same crystal would act as an end type material. And he used arsenic to dope the germanium, meaning he was introducing an impurity on purpose to alter the structure of the material to make it an effective semiconductor. He also found out that this introduced
boron to the material, which he found very interesting. His work would later become really important for power plants because the materials he was working with ended up being able to handle tremendous voltages, so they became very important in g S work with electricity generation. Hall's work with germanium lead him to develop technologies that were useful in the detection of gamma rays, something that was important both in nuclear physics and cosmology. Gamma rays are type of nuclear radiation.
It's electromagnetic radiation that typically comes from the radioactive decay of nuclei, and it is made up of photons, with the highest observed photonic energy we've seen so far. They also are an ionizing type of radiation, meaning the energy from gamma rays can strip away electrons from other atoms.
Ionizing radiation is potentially dangerous. It can cause cellular damage and potentially genetic damage to an organism subjected to them, not to mention increase the probability of cancer, so they're dangerous things. It's not as dangerous as alpha or beta waves, generally speaking, just because they didn't to pass right through stuff as opposed to getting absorbed. Really one area of
focus Hall dedicated himself too. In the early nineteen fifties, was working on a semiconductor device capable of producing light, a light emitting diode, in other words. A decade later, a colleague suggested to Hall that he used semiconductors to make a laser. Now in the nineteen fifties, Charles hard Towns showed how through the use of stimulated missions of radiation, he could create a maser sort of the microwave variant
of a laser. At In nineteen fifty nine, Gordon Gould published a paper suggesting it would be possible to create light amplification by stimulated emission of radiation or a laser. The basic idea is that you have to have some sort of lasing medium. We typically would use a gas or a crystal. Something like a ruby laser actually uses ruby crystals to do this. This is a material that will absorb energy, typically either light or heat than As it does so, the electrons and the material are excited
to higher energy states than their normal rest state. Now, this cannot continue indefinitely, and eventually the electrons will decay to a lower energy state, and those electrons, when they returned to their nor will energy state have to get rid of that excess energy. You can't just pump energy into electron, push it to a higher energy state and then it comes back down without getting rid of that
energy and has to admit it somehow. So they shed that excess energy in the form of photons or particles of light. Now those photons are not necessarily within the visible spectrum of light. You can create stuff like infrared lasers, for example, which are invisible to the naked eye. But the full technical details of lasers get way more complicated than this, But it's a pretty good basic explanation of what's going on and what Dr Hall was trying to achieve.
Only he was trying to do it with semiconductors, which no one had done yet to that point. All the ones that had been used had used flash arc lamps and other big pieces of equipment, but not semiconductors. So how did he do it well. I'll talk a little bit about that in just a second, but first let's take another quick break to thank our sponsor. Now, the first functioning laser debut in nineteen sixty and was the work of Theodore H. Meiman at Hughes Research Laboratories, but
early lasers did not use semiconductors. Hall would be pioneering new ground, and he himself was skeptical at first. He felt that optical efficiency of diodes was not nearly efficient or powerful enough. But Hall was intrigued and began to explore the possibilities, and as he researched lasers, he began to theorize away he might actually make a semiconductor injection based laser. He would need to create a gallium arsenid diode and have special mirrors to create this actual laser.
And he went to his bosses and he had this request. He said, hey, can I make a team and work on this project. He had absolutely no practical application for lasers. He didn't think of anything that they could actually use whose lasers for. But he thought it would be quote fun to work on end quote, so he pitched it and his bosses were intrigued, so they signed off on
his pet project and he got to work. After some intense research and development, Hall's small team of researchers produced a working laser using semiconductors, and they ran numerous tests. They refined their design, built a better model, and they wrote up their research. They published their work in a scientific journal. Meanwhile, at pretty much the same time, IBM announced it had created something that was almost but not
quite a working laser. However, they were very close to having it ready to go, and in an unusual move, both IBM and Hall's team would be awarded a patent for the technology. Hall's friend Nick holland Niak built off of Hall's work, using diodes made from gallium arsenide phosphied in an attempt to create a light emitting diode that could emit light in the visible spectrum. So the laser that Hall had created was an infrared laser, it was not something that was visible, and he would make the
first visible laser just a short while after. Hall's team demonstrated that semiconductor lasers were possible, but no one at this point knew what they would ever use lasers for, and at that time it was more about overcoming the engineering challenge and conducting various experiments to see what was possible.
The lasers Hall made were primitive by today's standards. They would only operate in the temperature of liquid air, which means you had to cool them down to below negative one four point thirty five degrees celsius, the boiling point that's in between liquid nitrogen and liquid oxygen. That wouldn't make a very practical laser for most applications because imagine that you would have to carry around a laser pointer that must always be connected to a cooling device that
kept everything at a ridiculously low temperature. It would be dangerous and inconvenient. In addition, Hall's team created a laser that worked in pulses. There was no real way to create a continuous laser using their approach. The team had made an enormous achievement, but would require the work of dozens more scientists and engineers to refine and improve designs to make lasers something that could find a use outside of laboratory demonstrations. As it turned out, the laser would
have numerous applications. This was something the team didn't have to worry about while they were working on developing the laser, but one of the most important applications was in the field of fiber optics. A fiber optic cable is a conduit for light. It is constructed in such a way as to guide light down a pathway made out of glass without losing too much in the process, but it requires a light source with a very narrow focus. Lasers
were the obvious solution to that problem. In addition, it wasn't difficult to insert patterns into laser light to represent information. This modulation made it possible to send information down a fiber optic line. Basically, the way it works is you have a computer system on one end. It takes data and then encodes that information in a way that can be transmitted via laser light down a fiber optic cable, so that data ends up modifying the laser light in
some way. It might be in phase, it might be impulses, it might be lots of different ways, and the laser light then zaps down this fiber optic cable. It travels at the speed of light to its destination some other computers somewhere else, and a receiver ends up detecting the incoming laser message through the fiber optics. A decoder takes that signal and transforms it back into useful information that the computer can actually process. Haul's semiconductor laser made all
of that possible. It's also the type of laser you might find in a CD layer, which my producer Tari would be very happy to hear about and her love of CDs. Another widespread application of semiconductor lasers is the barcode scanner. That's something we see in our day to day lives. Barcodes are great if you need a way
to keep accurate inventory management. You just slap a barcode unique to the type of material you're working with, and you scan everything into a system to establish your inventory, and then you can scan it again whenever you need to give it away, to use something or to sell something. So let's go with a grocery store example, because I think it's something that we can all identify with. You walk it to your grocery store and you go in there to buy something real tasty. Let's say it's um
spicy salsa. So you pick up a jar of your favorite brand. And by the way, and I'm being serious here, if you have a favorite brand of salsa, you need to tell me about it, because I am always on the lookout for a really good, flavorful spicy salsa. The hotter the better, but I wanted to taste good. Anyway, back to this example, more important stuff to talk about. You bring your jar of tasty salsa up to the
front of the store. Maybe you go through the self checkout lane, maybe you get in lines so that a cashier does the checkout process, but either way you soon reach the point where the jar is going to be scanned. A barcode scanner uses light to shine onto a barcode, and frequently it's a laser light. Barcodes consist of a series of lines of varying with the actual vertical bars. Those lines represent a numeric code associated with the product.
In this case, we're talking about salsa. So when the light shines on this barcode, the dark lines absorb some of that light. The white spaces between the dark lines reflect more of the light, and the barcode scanner isn't just emitting a laser light. There's also a photoelectric cell that detects the reflected light from a scan The cell creates a pattern of on off pulses that correspond to
the bars in the barcode. This gets translated to the scanner circuits to a numeric code that corresponds with that specific product. So the salza's price pops up on the cashier and or the cash register, and the system registers that one unit of salsa is leaving the building, and that updates the inventory, and the whole process makes sales and inventory management easier now. Like I said, not all
bar code scanners use lasers. Some use just led light, but most of the ones in high volume stores rely on lasers because they're reliable and their efficient. Hall ended up working on other stuff besides semiconductor lasers. He didn't just stop there. In the nineteen seventies, he worked on several research projects focused on photo voltaic technology as the United States was entering into an energy crisis at the time.
Photo voltaic cells convert light into electricity directly, So there are a lot of different ways you could potentially generate electricity using light, and many of those are indirect methods, where you're using light to heat something up and using that heat to generate electricity in some way. But as
I said, photo voltaics directly convert photons into electricity. Edmund Beckarel, a physicist in the nineteenth century, observed that certain materials would produce a small electric current if that material were exposed to light. Einstein himself wrote on the matter in nineteen o five, describing the nature of light and the
photo electric effect. Bell Labs would build early photovoltaic technology in the nineteen fifties, and the Space Race in the nineteen sixties fueled more research and development, but by the nineteen seventies the work was focused on finding ways to alleviate the pressure of the energy crisis to actually use it for the general public and not just for very specific uses like the space race. A photo voltaic cell
absorbs photons and emits electrons. Semiconductor material allows this to to turned into a useful electric current, which can be used to power all sorts of stuff or charge electric batteries. Hall would retire from General Electric in nineteen eighty seven, and his name is on more than forty patents. He won numerous awards, and he was inducted into the National Inventors Hall of Fame in nine. As I said at the top of the show, he passed away on November seven,
twenty sixteen, at the age of ninety six. But I also said the New York Times, which had interviewed Hall back in two thousand twelve in preparation for his obituary, you know, the one he didn't need yet because he
hadn't died yet. The death business is weird, guys, Anyway, The New York Times didn't hear of Hall's passing for nearly two years, only learning about his death when a researcher was updating that pre prepared obituary and seeing that now it's actually been nearly two years too late, And then they ran the obituary for a man who had
been dead for nearly two years. Because this world is crazy, but tech Stuff salutes Dr Robert in Hall, whose work made things like fiber optics, CD players, and laser pointers possible, among numerous other things. His contributions to engineering were significant, and throughout his life he considered himself an experimental scientist, which is pretty darn cool. If you guys have suggestions for topics I should tackle in future episodes of tech Stuff.
Maybe it's a technology or a company or a person in tech. Let me know. Maybe there's someone you would want me to interview or have on as a guest host. Send me an email. The addresses tech Stuff at how stuff works dot com, or drop me a line on Facebook or Twitter. The handle of both of those is tech stuff hs W. Remember to follow us on Instagram and you can go to twitch dot tv slash tech stuff to watch me record these shows live streaming over
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