Powerful Lasers and Their Uses

pronunciation at least once in every episode. So we got that all the way good to know we can go right into the actual meat of this episode. So I thought today we were going to cover some specific lasers

and explain what people are doing with those lasers. And I think most of us are familiar with the general concept of lasers, but we're gonna talk a little bit about how they work because it's important to understand the Bay six in order to get a deeper appreciation for the high powered lasers I'm going to talk about today, because we're talking about some of the most powerful lasers

in the world in this episode. So lasers are focused beams of light they're used in you know, wicked light shows like with Pink Floyd, or they're used to frustrate household pets. In science fiction, they're used either by or against robots and aliens or both. In the real world, they're used for all sorts of stuff, from conducting experiments too, in order to learn more about stuff like you know,

quantum effects, all the way to you know, removing unwanted hair. Now, it would not be an episode of tech stuff if I didn't take the opportunity to at least go over the basics of how a laser works. So tuck in here we go. The word laser used to be an acronym, so I guess technically it's still kind of is an acronym, but we recognize laser as being a noun all on its own, so you don't have to capitalize all the

letters the way you would with a typical acronym. The letters do stand for light amplification by stimulated emission of radiation. But what the heck does that mean? All right, this requires us to go back into some basic elementary school science stuff. You remember the structure of an atom, right, you that you got the nucleus in the middle. It's

made up of protons and neutrons. Around that nucleus orbit one or more electrons, depending upon which element you're talking about, whether or not it's an ion, the electrons and have it a space around the nucleus that we call the electrons orbital or its energy shell or energy level. So electrons can only have certain discrete values of energy. They cannot be you know, any value between two. It's one value, and then the next layer level up is another value,

and so on. They are discreet. Each energy shell can only hold a certain number of electrons. The shell closest to the nucleus is what we would call the K shell or the one shell. It can hold two electrons. Next out is an orbital that can hold an additional six electrons, so now you have up to eight total.

The third shell can hold an additional ten electrons, so you could have a possibility of eighteen electrons with three electron shells are orbiting an atom or nucleus, I should say not not orbiting an atom, because the atoms the whole thing. Anyway, each of those energy shells are important. It tells you the ground state for any given electron. It will always be at the lowest energy shell it

can inhabit. So if an energy shells full, so if that burst energy shells full, the electron has to be in the second shell or or higher, depending on how many there are there. Now, if you add energy to an atom, that energy would cause those electrons to move into higher in G shells, to move further out from the nucleus. So if you pump energy into atoms, the

electrons begin to move further out. And if you pump enough energy, and you could actually strip electrons away from atoms, at least temporarily, but you would then have a charged nucleus and you probably have some free electrons running everywhere. They would quote unquote want to get back together because those opposite charges would attract one another. But what happens if you stop adding energy to the atom, Well, the

electrons will return to their normal ground energy states. However, they cannot do that while still holding on to that energy you pumped into them. So first they have to release that excess energy in some way, and electrons do this by releasing photons, the particles of light. That's one

part that's really important to remember with lasers. The other big important thing to remember is that frequency or wavelength, and thus the color of light released is dependent upon both the lasing medium itself, what that material is made out of, and the energy difference between the excited state of the electron and its ground state. How much energy did you pour into this thing. Different atoms will release

different frequencies or colors of light. So, for example, if you excite the electrons in a ruby lazing medium that has a lot of chromium ions in it, it will produce a red light assuming you're doing the normal amount of energy pouring into this. Other lasing media will produce different wavelengths of light and thus different colors. That can include light that's actually outside the visible spectrum, so you can have lasers that are infrared lasers or ultraviolet lasers.

Those would be invisible to the human eye. But as I mentioned, the wavelength also also depends upon how much energy you pumped into the electrons before they return to their ground state. Now, unlike the light we would get from an incandescence source like a light bulb, all the photons from a lasing medium will be of the exact same wavelength, so they'll all be the same color. Moreover,

the photons are in are are coherent. That means that if you were to chart the waves of a laser, all the photons would match up with their crests and troughs in lockstep with one another. Normal visible light consists of photons of different wavelengths and they are not coherent. They are not moving at the same lockstep pace. The coherence of a laser allows it to remain focused in a tight beam over great distances. Directionality is another important

fact factor with lasers. Now that's in sharp contrast to the light from an incandescence source, which is diffuse not coherent. For your typical, you know, laboratory laser, the way you would stimulate the lasing medium is you would expose the lasing medium to an extremely intent flash of white light from powerful flash lamps for a fraction of a second. Typically,

this is called pumping the lasing medium. As you are pouring energy into the medium the collection of atoms and thus exciting the electrons in those atoms to higher energy states, and when they come back down they release these photons of the same wavelength and energy level. This process happens so fast that it's really hard to wrap your mind around it all or at least, it's very hard for me to do that because we're talking about times that are at one million of a second or even shorter

than that. So typically the goal is to excite electrons to an energy level two or three levels higher than their normal ground state. That increases what is called the population inversion. That is the relationship between the number of atoms that are in an excited state compared to those in the ground state. So we call it inverted because typically most atoms are in a ground state, but now we've inverted that where most atoms are in an excited state.

As the electrons calm the heck down, they release these photons of the same wavelength. Since that lasing medium is obviously made out of all the same stuff, these photons are locked together, so their wavefront's launching unison. That's what makes them coherent, and they are very directional. And this happens because of the stimulated emission part of lasers. So you've got an excited electron, it returns to its ground state,

it releases a photon of a certain wavelength. If that photon happens to run into an atom that also has an electron that was in that same excited state, the photon can stimulate that atom so that the photon the atom will emit when it's electron returns to its ground state, is going to vibrate the same as that first photon, and it will also move in the same direction as that first photon. Mirrors make up another important component in your typical laser. So let's think of a very simple laser.

Imagine you've got a tube and this tube is your laser. On either end of the tube, you have mirrors that are facing into the tube's center, and in the middle of the tube, you've got the lazing medium and you've got a big flash lamp pointed at this tube and it can shoot extremely intense white light at the lasing medium, which then ends up inducing this this uh laser to to begin this this you know, this stimulated a mission process to begin, and so you get photons that are

emitted by these excited atoms. They traveled down the tube, they hit a mirror, bounces back, and it passes through the lasing medium again and that gives it the opportunity to stimulate some more of the atoms that they too will release photons that will be in the same um wayfront, same direction as the initial photons. They'll continue down the tube, hit the mirror, bounce back, and this creates a cascade effect that can create more and more photons generating through

this laser. Now, one of those two mirrors is what we would call half silvered, which means the mirror will actually allow some of that light to pass through a reflecting the rest of it back in. So some of the laser light escapes through that and then can be in a focused beam, while other photons would still bounce back into the tube and continue the propagation of photons. So that's how lasers work. From a very very high level.

There are a lot of different details we could get into, like the fact that there are so many different types of lasing media like their solid state, there's gas lasing media, etcetera, etcetera. But what makes one laser more powerful than another, Well, that's a tricky question. What makes one laser a fun toy a like a laser pointer and another one powerful

enough to etch metal? Well, first, the energy level of photons produced by a lasing material is inversely proportional to the wavelength of the light produced when it is stimulated. When that lasing material is stimulated, So the higher the energy of the photon, the shorter the wavelength of that photon, and the wavelengths of visible light range from around the three range that would be in the violet part of the spectrum all the way up to seven nimes which

would be in the red part of the spectrum. So the further down roy g BIV you go, the higher the energy levels of the associated photons. So one thing that determines the power of a laser is the energy level of the photons, which depends upon the lasing medium and the amount of energy you're pouring into that medium

to produce the laser in the first place. So your power source is another factor to consider, and there's also the question of whether your laser is constant or a pulse laser that also affects the power of the laser beam. I'll talk more about pulse lasers a little bit later in this episode because it's a very important component of

the really powerful lasers we're going to talk about. So when we come back, I'm going to start talking about some of these really powerful lasers and what they're used for. But first let's take a quick break to thank our sponsor. At the University of Nebraska, there is an extreme Light laboratory, and in that lab there's an enormous device called the Diacles laser. It's named after the inventor of the parabolic reflector.

The parabolic reflector increases the intensity of reflected light. It's the most efficient way of doing it, the most powerful way of increasing the intensity of selected light that we've ever discovered. So according to the labs website quote, Diacles begins with a modest amount of energy with a short pulse, then stretches the pulse and sends it through a series of amplifiers and titanium sapphire crystals to pump up its power.

The secret to Diacles is high power. Is a compression stage where the stretched amplified pulse is compressed back into a very short, extremely powerful pulse. This trick prevents damage to the amplifiers. Then the powerful beam hits a parabolic

reflector that focuses its power to extreme intensities. I'll go more into this approach a little bit later with one of the other lasers, but the result of this is that you get a laser beam so powerful that it reportedly can produce light that is one billion times brighter than the light produced at the surface of the Sun itself. So what would you use the kind of a laser for. Would you use it to to blast a planet into

a billion pieces because it was in Alderon places rim shot. No, because that would actually require way more energy than even this beast could produce. The DIACLES is designed for scientific research, particularly in the realm of studying the interactions between light and matter. It's mostly used in an area called high field science. So what the heck is that? Well, the University of Nebraska is not the only place that does this. There's also the University of Michigan. They have a Center

for Ultra Fast Optical Science. They break down high field science as science revolving around conditions that include high energy density, and that involves getting a better understanding of non equilibrium systems as well as a deeper understanding of electron behaviors. So this has the potential to have many different applications in the future relating to cool stuff nanotechnology. Plus, well, we don't even know what we don't know yet, so we might find other really nifty things to do with it.

One thing, this laser can do right now? Is vapor us stuff real good? Actually, I should say it can excite matter to convert it to plasma. Plasma is the most plentiful form of matter in the universe. Matter heats up to incredible temperatures under the intensity of this laser, and it also has its pressure increased dramatically, and at that point the material converts into a gas through which free electrons can flow. That is plasma. So plasma is sort of you can think of it as almost a

subtype of gas. It's more than just gas because you have this condition where you have high energy in there, so you've got a lot of free electrons flowing around. You have a typically a net neutral electric charge plasma, but it means it can actually conduct electricity itself. This is the stuff of stars. Stars are made of plasma, So you're talking incredibly high temperatures and pressures in the research team at Nebraska used this particular laser to conduct

a super interesting experiment. They wanted to find out what would happen if you bombarded the same electron with numerous photons. And this is I have to stress wicked hard to do. An electron is a pretty darn tiny target. Now. I'm not going to get into the size of electrons here because that alone is a complicated issue and involves things like wave functions. But anyway, it's it's really really super small.

Near typical electron rarely encounters a photon. It might get struck by a photon three times a year, so every four months or so, this electron might run into a photon, but otherwise eyes know. The team, however, wanted to pelt the heck out of electrons. They wanted to study the scatter effect that the electron would have on photons. The scatter effect is what happens when light strikes a surface.

The light scatters after it hits a surface, and our eyes can pick that light up, and that's how vision works. You can see stuff because light scatters off of it in various ways. Now, the team was doing the same thing, except instead of using a general light source like a lamp and a macro sized object like say a couch or something, they were using this super powerful laser as

the light source an electron beam as their target. Now, according to the University of Nebraska's newspaper, the team was able to scatter nearly one thousand photons off the same electron, and according to the team, the behavior of both the photons and the electron fell outside the normal reactions, which is pretty interesting in science. Anything that is outside the

normal result is interesting. Now, if you're unlucky, if you haven't been super careful or or something has gone wrong, your observations might be indicative of an experimental error somewhere, like maybe you made a mistake, maybe some of your equipment wasn't working. But if you are lucky, you did everything properly, all your equipment works. What you were actually seeing is legitimately a new observation of a real phenomenon.

So the team discovered that once laser light passed a certain power threshold, it would scatter off of electrons in interesting ways. Now, typically light from a source will scatter in a predictable way at the same angle and energy it possessed before the collision, no matter how intense the light.

So think of it as a dimmer switch. If you have a dimmer switch on installed, and you're looking at say a table and low light, As you intensify the light, the table's shape doesn't change, its color doesn't change, it it brightens, so you might get more of a view of what the color is, but it doesn't change in any real phenomenal way. Uh, that was not what they

were seeing. They were getting a totally different result. So if we could scale this up like their results and observe it with our eyeballs instead of with super sensitive you know, sensors, it would mean that if you were to use that same dimmer switch, you could see that as you turned the light past a certain level of intensity, the thing you're looking at that table would actually appear to change shape and color because you were using light

that was of that great intensity. That's essentially what they found, except again, they weren't using diffuse light. They were using a super focused, very high powered laser, and they weren't looking at a macro object. They were looking at electrons. The team also observed that the electron being pummeled by photons would release its own photon, so the electron would become stimulated in other words, but that this ejected photon would begin to absorb the energy of the scattered photons

from the laser. This transformed the energy and wavelength of the ejected photon, and it would turn into an X ray. Now, according to the researchers. Such an X ray could have

useful applications in nanotechnology. The X ray only lasts for a short moment, but has an extreme amount of energy, and it could be used to help create three dimensional images of stuff on the nanoscopic scale, and that would be phenomenal because the nanoscale is so small that at the lower end of it, you're dealing with stuff that's actually smaller than the wavelength of visible light, which is why you cannot use an optical microscope to look at

stuff that's on the nanoscale. The wavelengths of light are just too big to pick up the objects you're actually looking for, so that's kind of crazy. But this could potentially allow people to create three dimensional visualizations of objects that are on the scale. It could also have other practical applications, including medical ones. It could allow X ray technicians to create images at a much higher resolution, which would be really useful to look for stuff like micro fractures.

For example, the standard X ray machine might not be able to detect because it wouldn't have that level of resolution. It could also be used in other applications, such as in security systems to scan for potential weapons or other security threats, and it's increasing our understanding of physics in general, which could lead to practical applications we can't even anticipate. So that's Diacles. But we have more to talk about in just a moment. Let's take a quick break to

thank our sponsor. Earlier I mentioned the University of Michigan's Center for Ultra Fast Optical Science. That's the home of another incredibly powerful laser. This one is called the Hercules laser. It's a high field pedal what class laser? A pedal? What, by the way, is a billion million whats and a what corresponds to the power and electric circuit in which the potential difference is one vault and the current is one amp here. So we're talking very high energy laser here.

This laser is used in the LABS research programs to quote explore the ultra relativistic intensity regime of laser matter interaction. In to quote, huh, what the heck does ultra relativistic mean? While as you might guess, it does refer to the theory of relativity, A particle is said to be ultra relativistic when it is advanced to the speed that's really close to the speed of light when you get it super super fast, about as close to the speed of

lights you can possibly manage. Einstein, of course, told us the speed of light is essentially the speed limit for all the stuff in our universe. In two thousand seven, the engineering team at the University of Michigan generated a laser with the power of three hundred terra wats, and it started off an era of ultra powerful laser experiments. The team holds the world records for highest focused intensity of a laser and the amplified spontaneous emission temporal contrast.

I have no idea what that second thing means, if I'm being honest, but it does sound wicked dope. Remember earlier when I talked about how a laser's power depends partly on whether it is pulsed or a constant. Well, the Hercules laser relies upon a type of amplification called chirped pulse amplification. So this gets super technical, and I, frankly I do not understand all of it. So we're gonna go super high level because that's all my primitive reptile brain can handle. I'm gonna do my best to

explain it as I understand it. So many apologies to all the high high field physics experts out there, all the laser engineers out there, give me a whole lot of slacks. So the goal is to use very short pulses of energy to create this laser and then amplify those pulses to get an output energy level that typically would only come from a longer pulse of energy. Now, when I say short pulses, i'm talking crazy short. We're talking on the femto second scale. A fempto second, by

the way, is one quadrillionth of a second. It's an incredibly short amount of time. The fempto second laser pulse that starts things off has a very high peak power level and as well as the other stuff that comes with that like electric fields and stuff. But these qualities actually make those super short pulses potentially harmful to laser components like optics, and it can also cause beam distortion.

So your output, your goal for your output is to get the super high powered laser, but the energy representing those pulses could end up tearing apart the very components of the user that you rely upon. So here's the solution, and I mentioned it in the Diocles one as well. That description talked about this. It's using a reversible process to effectively stretch out the laser pulse for the amplifier. And when you stretch out the laser pulse, it's not

just dealing with a pulse that lasts longer. The energy level is reduced as well. So the amplifier, as the name suggests, amplifies that incoming signal so that the outgoing signal is much greater. It does this by ending up, you know, the lasing medium ends up ejecting these photons, all of the same wavelength and the same energy level. Uh,

and they all are going through in the same process. Now, before it actually emerges from the laser, it needs to go through another system to compress that pulse to intensify the peak power of the outgoing laser. So you're doing the reverse of the stretching process that I mentioned a second ago. And by compressing the pulse back to its original length, you also increase its peak power back to

its original peak power. So such a laser has an optical stretcher and an optical compressor in order to do this. So how do those work? Beats me, I read a whole paper on it, and my brain is still buzzing. And I don't even have the beginning levels of comprehension for this. This is way outside my level of expertise. However, the outcome is that we can now build lasers with incredibly high peak power outputs that otherwise would have been impossible.

So the research team has two different test chambers that the hercules can fire a laser into. One test chamber is for gases and the other one is for solids. Both chambers are surrounded by radiation shielding in the form of cement walls, but the gas chamber has a secondary level of shielding made up from lead bricks to help block any potentially harmful radiation that would result from collision experiments. The team is using this UH laser to learn more

about these high powered interactions between matter and light. Some of what they learned might be useful in future applications, ranging from studying rapidly changing conditions within a plasma all the way to absorption spectroscopy, which is UH the group of methodologies we used to determine the measure of radiation absorption of various materials and hey while I've been covering some super high tech lasers that are pushing our understanding

of physics into new territory. I'm gonna also mention one that might be used for less scholarly applications. That would be the Athena laser from Lockheed. This prototype laser quote uses Lockheed Martin's thirty kilowatt accelerated laser demonstration initiative, a k Aladdin spectral beam combining fiber laser in which multiple fiber laser modules form a single, powerful, high quality beam, providing great efficiency and lethality in a design that scales

to higher power levels. End quote. That's terrifying, great efficiency and lethality. Now it's a prototype laser weapon system that is designed to defeat close in, low value threats such as improvised rockets, unmanned aerial systems, vehicles, and small boats. It's also a quote from Lockheed Martin. So essentially, this device can can fire an incredibly intense beam of light at a target and it has the goal of either dazzling, damaging,

or destroying the target. So you're either trying to disrupt it's it's optical systems so it can't find a target or you're disabling it in some way or outright destroying it. The system relies on an infrared tracking camera to aim the laser at the target. For slower moving targets like a boat or an unmanned drone, a human operator would be allowed to verify that the target is in fact

a potential threat before the system would actually fire. For more immediate threats like improvised rockets or mortars, where time is of the essence, the system would operate in an autonomous mode, and the system has been demonstrated a few times. I actually watched a video of the Athena targeting system and watched as it brought down a drone that was designed to look kind of like your standard aircraft had

wings and a tail section. So Athena would target the stabilizing fin on the tail of this unmanned aerial drone and using this very high powered laser, it damaged the fin, actually burned the fin off in a couple of examples pretty quickly, and that caused the drone to plummet to the earth and lock. It has also shown that such a laser could even melt clean through the engine blow of a truck. Now the prototype is a proof of concept, and this laser isn't anywhere close to being a handheld weapon.

This is not something you would give a soldier and say head out there and take down that tank. It's a pretty big device. It would fit on like a warship, but it would require some mantorization to fit on a tank or truck and not be so cumbersome and heavy that it would make operating the vehicle difficult. So we've got a long way to go before this gets deployed anywhere beyond very very large platforms, like I said, like

on warships or something. Still, this could be an indication pointing toward the future of warfare where weapons work at the speed of light and can burn through solid steel

in a matter of moments. But while there are destructive uses for powerful lasers, a lot of the ones I've looked at are meant to conduct scientific research or directly help with goals like making a practical fusion reactor or majorizing particle accelerators so that you don't have to build a facility the size of the large hadron collider in Europe. So there are a lot of scientific, constructive methods and

uses for lasers. So I'm very interested to learn more about those and maybe someday getting a better grasp on some of the more complicated factors like the lazing methodologies Hope springs Eternal. If you guys have any suggestions for future episodes of tech Stuff, visit our website. It is text stuff podcast dot com. Try does a great job. On that website, you can find ways to contact the show,

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