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CTD - Laser Principles


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I think I'm a little confused about the diode part. Is the laser core the same as the diode (e.g. the laser core is a big semiconductive crystal), or are the diodes separate and are used to excite the laser core (e.g. the diodes emit flashes of light to excite the laser core)? I think the term "The laser crystal" in paragraph 2 is what's throwing me off- maybe it should be changed to "This 'laser core'"? Edited by Astyanax
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[quote name='Astyanax' date='Jun 30 2005, 11:46 AM']I think I'm a little confused about the diode part.  Is the laser core the same as the diode (e.g. the laser core is a big semiconductive crystal), or are the diodes separate and are used to excite the laser core (e.g. the diodes emit flashes of light to excite the laser core)?  I think the term "The laser crystal" in paragraph 2 is what's throwing me off- maybe it should be changed to "This 'laser core'"?
[right][post="123669"]<{POST_SNAPBACK}>[/post][/right][/quote]
The laser core is the stack of diodes made from succesive deposited layers of diamond, layers alternating positive and negative. The layers form a single monocrystalline unit, though
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All right, I think I understand that part now. Thanks for the explanation, dan2. Sorry for making you explain everything to me here, but in Active, you and Kikanaide were having a very technical discussion that was way over my head, so I pretty much assumed you guys knew what you were talking about because I didn't have much to add. Now, in order to proofread this text effectively, I can't make that assumption, so I need to be walked through this. Baby-steps, preferably. :D

On that note, could you explain to me why monocrystalline diamond LED's make better lasers? In the text, the only reasons monocrystalline diamonds make better lasers are because 1.) they can make larger crystals, and 2.) they are more efficient.

#1's case is fairly straightforward, but #2 is never really explained. I'm guessing that a monocrystalline structure reduces the amount of energy lost to heat (less light is absorbed by the crystal?), but in what other way is it efficient?

Also, paragraphs 2 and 4 mention "[b]laser[/b] emitting diodes". Is this a correct term? I didn't think diodes could emit monodirectional light, or is this a technological advancement that makes lasers practical/feasible? Edited by Astyanax
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[quote name='Astyanax' date='Jul 6 2005, 01:21 PM']A)On that note, could you explain to me why monocrystalline diamond LED's make better lasers?  In the text, the only reasons monocrystalline diamonds make better lasers are because 1.) they can make larger crystals, and 2.) they are more efficient.
#1's case is fairly straightforward, but #2 is never really explained.  I'm guessing that a monocrystalline structure reduces the amount of energy lost to heat (less light is absorbed by the crystal?), but in what other way is it efficient?
B)Also, paragraphs 2 and 4 mention "[b]laser[/b] emitting diodes".  Is this a correct term?  I didn't think diodes could emit monodirectional light, or is this a technological advancement that makes lasers practical/feasible?[/quote]
A) If you buy one of those pesky laser diodes from any dollar store, usable to annoy your neighbours pets, when you disassemble it, you'll see it contains a tiny, tiny crystal of gallium arsenide. Because the crystal is very small, even if you use a high voltage, it is able to transform only a certain amount of electrical energy into light, the rest being used to generate heat. I'm not talking about is nominal voltage, at which is very, very efficient, but something like oversaturating the crystal. If you have a much larger crystal, it's nominal output would me much higher, therefore it will stay in the very efficient domain instead of being oversaturated for very high voltages. Of course, an oversaturated laser diode would probably stop functioning really fast, too.
B)I'm not sure if it's not better laser diode, but what's wrong with laser emitting diode?
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So what you're saying is that a larger diode should be able to achieve a higher voltage before "oversaturating" it? And that "oversaturation" will result in a lot of waste heat? And a new "process" allows the X-Corps to create larger crystals than previously? Ok, I think I'm getting the picture now.

About "[i]laser[/i] emitting diodes"... Well, I've heard of "[i]light[/i] emitting diodes", or LEDs, and from what I understand, the light emitted is [b]not[/b] monodirectional. Instead, it's focused by its plastic sheath.

Now "laser emitting diode" sounds to me that the light emitted from the diode [b]is[/b] monodirectional and already amplified. But the amplification doesn't come from the diodes- it comes from the mirrors on each end, right? Edited by Astyanax
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Amplification comes from the generation of the beam itself, those photons on the right direction (perpendicular to the mirrors) help more and more photons to be emmited on the same direction.
Yes, in laser LEDs, the light is not generated monodirectionally, but that's because of the shape and (un)transparency of the crystal. If the crystal would be diamond, the resulting light would be already monodirectional.
Think of it as a cross-breed between crystal lasers and LED lasers.

Darn, Pardus takes too much of my time :)
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[quote]Yes, in laser LEDs, the light is not generated monodirectionally, but that's because of the shape and (un)transparency of the crystal. If the crystal would be diamond, the resulting light would be already monodirectional.
Think of it as a cross-breed between crystal lasers and LED lasers.[/quote]

Not quite true... From what I've read of the literature, the reason it's not mono-directional because of the construction of the laser emitting diode layer... However, there's a version of the Laser Emitting Diode that could potentially change that. It's called the Vertical Cavity Surface Emitting Laser Diodes (VCSELs).
Here's a link to the rather comprehensive [url="http://repairfaq.ece.drexel.edu/sam/laserdio.htm#diocss8"]Laser FAQ[/url] describing it. Also, we could think about hybriding it, a diode pumped solid state laser.

*edit* The more I read about it, more more I find Diode Pumped Solid State Laser to be ideal for use in laser weapons. It apparently has higher energy output than just diode lasers... Here's a url:[url="http://repairfaq.ece.drexel.edu/sam/laserssl.htm#ssldps"]Diode Pumped Solid State Lasers[/url] Edited by tzuchan
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[quote name='tzuchan' date='Jul 12 2005, 10:00 PM'][quote]Yes, in laser LEDs, the light is not generated monodirectionally, but that's because of the shape and (un)transparency of the crystal. If the crystal would be diamond, the resulting light would be already monodirectional.
Think of it as a cross-breed between crystal lasers and LED lasers.[/quote]
Not quite true... From what I've read of the literature, the reason it's not mono-directional because of the construction of the laser emitting diode layer...
[/quote]
:blink:
OK, feel free to edit/change the text, I don't mind
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Guest Azrael
This is going nowhere, this is not Active, don't add unnecessary things to the text, I have read through it and your posts, and I don't see anything important, rather than maybe a line correction or two, any important corrections? (and I mean [i]corrections[/i], not more overcomplicated additions)
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Guest Azrael
Can anyone please post why these changes are necessary? I got lost. Please have it be short, my mind starts to wander about when the explanations turns into the realm of unnecessary overcomplication.
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Well, there are parts that confused me when I read over it, so I started off the discussion to make sure that I [i]really[/i] understand what's going on (so I can properly proofread the laser texts for consistency) as well as ensure the text is explaining things clearly.

I haven't suggested any changes in recent memory, but I can't comment on the latest stuff because I haven't had a chance to looked it up yet. But "Aye, aye, Sir," I'll try keep the inclusion of new material to a minimum.
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  • 3 weeks later...
I've read up on those VCSEL and DPSS lasers, but I think trying to adequately explain them in the text would make it longer and more complicated than necessary.

I've made some changes in this version of the text aside from a few spelling and grammar corrections. "Laser emitting diode" was changed to "laser diode" to prevent confusion with LEDs (a quick Google search found more instances of “laser diode” than “laser emitting diode”). "In cascade" isn't quite the correct term (as Kikanaide noted in a PM)- I've replaced it with "sequentially", though "serially" or "successively" might also be acceptable. I’ve also reworked paragraph 4 and 5. I hope it reads better now and better addresses tzuchan's comment about "a new Laser Emitting Diode Design". Apologies to dan2 for brazenly modifying his text. :P

On another note, should we add a line mentioning "secondary capacitors"? Paragraph 5 touches on the subject, but it implies many capacitors, rather than just 2 (the laser defense facility has three, but that's addressed in that text).

[quote]Laser Principles
X-Net://Pegasus.net/Alien/Weapons/Laser Principles

Several decades of new discoveries in science, technology, and engineering have provided the tools for the creation of high-energy lasers (HELs), a significant contribution toward the improvement of our security. Due to the difficulties involved in generating enough light intensity with a portable device, lasers that do more than blinding the target have been just a science-fiction dream until now.

Current LASER (Light Amplification by Stimulated Emission of Radiation) technology works by passing a strong electrical current through stacked [color="blue"]laser diodes[/color]. The laser crystal is housed in a tube filled with a highly transparent and heat conductive liquid, and is capped with a fully reflecting mirror on one end and a partial mirror on the other.

At the atomic level, the difference of potential in the crystal helps electrons to get promoted to higher energy levels, in a metastable state, but return gradually to their initial energy, the excess being released as photons. Those photons that do not have their direction perpendicular to the mirrors are quickly lost as heat, but those that do, rebound from one mirror to the other allowing more and more metastable atoms to lose their energy as photons having the same direction with the incident photons. The result is an exponential growth in the number of photons of the same wavelength, phase and direction. Once the light intensity reaches a threshold, it can pass through the partially mirrored end in a highly focused beam.

Our research has uncovered a way to manufacture laser crystal[color="blue"]s that are[/color] significantly more [color="blue"]powerful[/color], efficient, and durable than previous ruby- or carbon dioxide-based devices. [color="blue"]This new technique of growing synthetic diamond laser core crystals with alternating layers of positive (beryllium and boron) and negative (nitrogen and oxygen) dopants allows us to greatly exceed the size of the crystals used previously for laser diodes and increase the laser output tremendously.[/color]

[color="blue"]Combined with recent advances in the material science that allowed the development of power capacitors based on high temperature superconductors, our newest laser prototypes can store more than enough energy to last through a lengthy engagement.[/color] These capacitors are connected [color="blue"]sequentially[/color], [color="blue"]gradually transferring[/color] electricity to the laser core and greatly improving the safety of the user by preventing accidental discharges.

[color="blue"]Lasers deliver the bulk of their energy[/color] to a relatively small spot, proportional with the size of the laser crystal, about one centimeter in diameter. In the past, the typical melt-through time for a thick metallic object was about 10 seconds; however, the improved capacitors dump the stored energy in less than a fraction of second, [color="blue"]resulting in a laser beam capable of vaporizing[/color] a hole through a 10 centimeters thick steel plate within milliseconds.

The fact that laser weapons have almost no moving parts results in a weapon that is not only easier to maintain, but also more reliable than conventional weapons. The loss of accuracy due to the time delay required by the electricity transfer through capacitors is [color="blue"]partially[/color] compensated by the lack of recoil. Improving the accuracy of laser weapons is just a matter of perfecting the technology involved in this rate of transfer.

It is extremely important to realize the extent of this technology within the X-Corps. Appropriately developed and applied, high-energy laser systems can become an important contributor to the defense of our world. Complete and successful development of directed energy weapons will require extensive testing, both in the laboratory and in the field to mature all the technologies involved, and to apply the growing capabilities in the most efficient way.

"I knew something must have gone right, because James was trying to dance with me. He opened a bottle of red wine - he doesn't like champagne - he opened the bottle, and he yelled to everybody,'Hey, Marshall, Noushin, get over here you greasemonkeys, I have great news.' And then he told us the lab had finally worked out the physics of a combat-grade laser, and they were ready for the prototype stage. He pointed at the pile of scrap metal he'd been using as a table for the wine, and he said this new diamond laser could go through it like butter. We were so excited, we had a working model constructed by the end of the day."
- Maria Iglesias, Ph.D, Senior Technician[/quote]
Edit- in retrospect, I think it would be make more sense if paragraphs 5 and 6 were switched since paragraph 4 ends with increased laser output, which flows better to paragraph 6's laser beam discussion. Paragraph 5 is about energy storage and safety measures, which would then flow into paragraph 7's discussion of increased reliability and possible accuracy improvements.

Edit2- took tzuchan's comments into consideration. Changed "don't" to "do not" and tweaked paragraph 6's first sentence slightly- "beam" is a bit vague. Edited by Astyanax
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Just one quick grammer nitpick here:
[quote]At the atomic level, the difference of potential in the crystal helps electrons to get promoted to higher energy levels, in a metastable state, but return gradually to their initial energy, the excess being released as photons. Those photons that [color="blue"]do not[/color] have their direction perpendicular to the mirrors are quickly lost as heat, but those that do, rebound from one mirror to the other allowing more and more metastable atoms to lose their energy as photons having the same direction with the incident photons. The result is an exponential growth in the number of photons of the same wavelength, phase and direction. Once the light intensity reaches a threshold, it can pass through the partially mirrored end in a highly focused beam.[/quote]
In general, contractions like don't, won't, etc shouldn't be used in formal reports.

Aside from that, I don't see anything that needs improving.

I'm not too sure about the paragraph switching part, mainly because para 6 refers to the improved capacitors, which is discussed in para 5. However, if we remove para 6 entirely, and move the difference in laser beam power sentence to para 4 might make it flow better. In particular since the capacitors are importent for handheld laser weapons, but upgraded laser crystals are important to laser weapons, and is the most important factor is power input to laser strength.
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Good points, tzuchan. I admit that I only read the first half of paragraph 6 when I was looking at the structure :Blush:, and I think you're right that the paragraphs don't need to be switched. I've edited in some small changes in my previous post.

One last thing- in paragraph 6, sentence 1:
[quote]Lasers deliver the bulk of their energy to a relatively small spot, proportional with the size of the laser crystal, about one centimeter in diameter.[/quote]Isn't the "energy delivered to the small spot" also dependent on how far away the target is? Edited by Astyanax
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Depending on the type of laser, yes.
Generally, the whole concept of lasers in the first place was that due to the fact that the individual photons in the beam are parellel or near parellel to each other, aka is coherent, there will be little to no dispersion of the beam, that is to say that the beam will have the same cross section no matter how far it is from the emitter. However, the type of laser diodes currently in use(in laser pointers at least, not the VCSEL) generates a laser beam that is acually not competely coherent.

Anyway, putting that sort of excess data aside, in my opinion, in laser weapons, you'd want to have a as coherent as possible beam. Both to increase effective range, and to increase damage. In which case, I'd think that the scientists on the Laser Weapons project would have designed a system to generate a near perfectly coherent beam.
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Another question comes to mind, though. The laser aircraft weapon has such a short range; if the laser is virtually no beam dispersion, why is the range so small? Theoretically, the range should be very long.

I guess you could say that particulates and water vapor in the air reduce the energy of the beam...?
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[quote name='Astyanax' date='Aug 6 2005, 10:52 AM']Another question comes to mind, though.  The laser aircraft weapon has such a short range; if the laser is virtually no beam dispersion, why is the range so small?  Theoretically, the range should be very long.

I guess you could say that particulates and water vapor in the air reduce the energy of the beam...?
[right][post="127666"]<{POST_SNAPBACK}>[/post][/right][/quote]
In fact, that is theoritically the one and only drawback of laser weapons. Dust, steam, smoke, even difference in air temperature can cause light to deflect and disperes. But in space, laser weapons might have a very very long effective range. Well, at least up to a few light seconds. After that, you'd have to lead the target abit.
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Okey dokey. In that case, it would probably be a good idea to mention this limitation in the text. I'm thinking the end of paragraph 3 might be a good place...?

I'm a bit verbose at the moment; any ideas on how to make this less technical? I do like how it flows into paragraph 4, though.
[quote name='Paragraphs 3-4']At the atomic level, the difference of potential in the crystal helps electrons to get promoted to higher energy levels, in a metastable state, but return gradually to their initial energy, the excess being released as photons. Those photons that do not have their direction perpendicular to the mirrors are quickly lost as heat, but those that do, rebound from one mirror to the other allowing more and more metastable atoms to lose their energy as photons having the same direction with the incident photons. The result is an exponential growth in the number of photons of the same wavelength, phase and direction. Once the light intensity reaches a threshold, it can pass through the partially mirrored end in a highly focused beam. [color="blue"]Though such a beam should have a range far superior than any weapon we possess, the clarity of the medium that lasers must pass through affects the effective range.  Water vapor and particulates in the air, such as dust, smoke, and smog, all adversely affect the effective range of any laser-based weapon.  Every particle in the path of the beam absorbs a small fraction of its energy, essentially leeching away the carefully focused power of the laser.  Until now, older laser designs lacked the power to overcome this phenomenon and could not be adapted for battlefield use.

New[/color] research has uncovered a way to manufacture laser crystals that are significantly more powerful, efficient, and durable than previous ruby- or carbon dioxide-based devices. This [s]new[/s] technique of growing synthetic diamond laser core crystals with alternating layers of positive (beryllium and boron) and negative (nitrogen and oxygen) dopants allows us to greatly exceed the size of the crystals used previously for laser diodes and increase the laser output tremendously.[/quote] Edited by Astyanax
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  • 10 months later...

Latest version (minor changes to paragraphs 3-4):

 

Laser Principles

X-Net://Pegasus.net/Alien/Weapons/Laser Principles

 

Several decades of new discoveries in science, technology, and engineering have provided the tools for the creation of high-energy lasers (HELs), a significant contribution toward the improvement of our security. Due to the difficulties involved in generating enough light intensity with a portable device, lasers that do more than blinding the target have been just a science-fiction dream until now.

 

Current LASER (Light Amplification by Stimulated Emission of Radiation) technology works by passing a strong electrical current through stacked laser diodes. The laser crystal is housed in a tube filled with a highly transparent and heat conductive liquid, and is capped with a fully reflecting mirror on one end and a partial mirror on the other.

 

At the atomic level, the difference of potential in the crystal helps electrons to get promoted to higher energy levels, in a metastable state, but return gradually to their initial energy, the excess being released as photons. Those photons that do not have their direction perpendicular to the mirrors are quickly lost as heat, but those that do, rebound from one mirror to the other allowing more and more metastable atoms to lose their energy as photons having the same direction with the incident photons. The result is an exponential growth in the number of photons of the same wavelength, phase and direction. Once the light intensity reaches a threshold, it can pass through the partially mirrored end in a highly focused beam. Though such a beam should theoretically have an infinite range, water vapor and particulates in the air, such as dust, smoke, and smog, reduce the effective range of any laser-based weapon.  Each particle in the path of the beam absorbs a small fraction of its energy, essentially leeching away the carefully focused power of the laser.  Until now, laser designs lacked the power to overcome this phenomenon.

 

New research has uncovered a way to manufacture laser crystals that are significantly more powerful, efficient, and durable than previous ruby- or carbon dioxide-based devices. This technique of growing synthetic diamond laser core crystals with alternating layers of positive (beryllium and boron) and negative (nitrogen and oxygen) dopants allows us to greatly exceed the size of the crystals used previously for laser diodes and increase the laser output tremendously.

 

Combined with recent advances in the material science that allowed the development of power capacitors based on high temperature superconductors, our newest laser prototypes can store more than enough energy to last through a lengthy engagement. These capacitors are connected sequentially, gradually transferring electricity to the laser core and greatly improving the safety of the user by preventing accidental discharges.

 

Lasers deliver the bulk of their energy to a relatively small spot, proportional with the size of the laser crystal, about one centimeter in diameter. In the past, the typical melt-through time for a thick metallic object was about 10 seconds; however, the improved capacitors dump the stored energy in less than a fraction of second, resulting in a laser beam capable of vaporizing a hole through a 10 centimeters thick steel plate within milliseconds.

 

The fact that laser weapons have almost no moving parts results in a weapon that is not only easier to maintain, but also more reliable than conventional weapons. The loss of accuracy due to the time delay required by the electricity transfer through capacitors is partially compensated by the lack of recoil. Improving the accuracy of laser weapons is just a matter of perfecting the technology involved in this rate of transfer.

 

It is extremely important to realize the extent of this technology within the X-Corps. Appropriately developed and applied, high-energy laser systems can become an important contributor to the defense of our world. Complete and successful development of directed energy weapons will require extensive testing, both in the laboratory and in the field to mature all the technologies involved, and to apply the growing capabilities in the most efficient way.

 

"I knew something must have gone right, because James was trying to dance with me. He opened a bottle of red wine - he doesn't like champagne - he opened the bottle, and he yelled to everybody,'Hey, Marshall, Noushin, get over here you greasemonkeys, I have great news.' And then he told us the lab had finally worked out the physics of a combat-grade laser, and they were ready for the prototype stage. He pointed at the pile of scrap metal he'd been using as a table for the wine, and he said this new diamond laser could go through it like butter. We were so excited, we had a working model constructed by the end of the day."

- Maria Iglesias, Ph.D, Senior Technician

Edited by Astyanax
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  • 1 month later...
Guest Azrael

LASER PRINCIPLES

X-Net://Pegasus.net/Alien/Weapons/Laser Principles

 

Several decades of new discoveries in science, technology, and engineering have provided the tools for the creation of High-Energy Lasers (HELs), a significant contribution toward the improvement of our security. Due to the difficulties involved in generating enough light intensity with a portable device, lasers that do more than blinding the target have been just a science-fiction dream until now.

 

Current LASER (Light Amplification by Stimulated Emission of Radiation) technology works by passing a strong electrical current through stacked laser diodes. The laser crystal is housed in a tube filled with a highly transparent and heat conductive liquid, and is capped with a fully reflecting mirror on one end and a partial mirror on the other.

 

At the atomic level, the difference of potential in the crystal helps electrons to get promoted to higher energy levels, in a metastable state, but return gradually to their initial energy, the excess being released as photons. Those photons that do not have their direction perpendicular to the mirrors are quickly lost as heat, but those that do, rebound from one mirror to the other allowing more and more metastable atoms to lose their energy as photons having the same direction with the incident photons. The result is an exponential growth in the number of photons of the same wavelength, phase and direction. Once the light intensity reaches a threshold, it can pass through the partially mirrored end in a highly focused beam. Though such a beam should theoretically have an infinite range, water vapor and other particles in the air, such as dust, smoke, and smog, reduce the effective range of any laser-based weapon. Each particle in the path of the beam absorbs a small fraction of its energy, essentially leeching away the carefully focused power of the laser. Until now, laser designs lacked the power to overcome this phenomenon.

 

New research has uncovered a way to manufacture laser crystals that are significantly more powerful, efficient, and durable than previous ruby- or carbon dioxide-based devices. This technique of growing synthetic diamond laser core crystals with alternating layers of positive (beryllium and boron) and negative (nitrogen and oxygen) dopants allows us to greatly exceed the size of the crystals used previously for laser diodes and increase the laser output tremendously.

 

Combined with recent advances in the material science that allowed the development of power capacitors based on high temperature superconductors, our newest laser prototypes can store more than enough energy to last through a lengthy engagement. These capacitors are connected sequentially, gradually transferring electricity to the laser core and greatly improving the safety of the user by preventing accidental discharges.

 

Lasers deliver the bulk of their energy to a relatively small spot, proportional with the size of the laser crystal, about one centimeter in diameter. In the past, the typical melt-through time for a thick metallic object was about 10 seconds; however, the improved capacitors dump the stored energy in less than a fraction of second, resulting in a laser beam capable of burning a hole through a 10-centimeter thick steel plate within milliseconds.

 

The fact that laser weapons have almost no moving parts results in a weapon that is not only easier to maintain, but also more reliable than conventional weapons. The loss of accuracy due to the time delay required by the electricity transfer through capacitors is partially compensated by the lack of recoil. Improving the accuracy of laser weapons is just a matter of perfecting the technology involved in this rate of transfer.

 

It is extremely important to realize the extent of this technology within the X-Corps. Appropriately developed and applied, high-energy laser systems can become an important contributor to the defense of our world. Complete and successful development of directed energy weapons will require extensive testing, both in the laboratory and in the field to mature all the technologies involved, and to apply the growing capabilities in the most efficient way.

 

"I knew something must have gone right, because James was trying to dance with me. He opened a bottle of red wine - he doesn't like champagne - he opened the bottle, and he yelled to everybody, ‘Hey, Marshall, Noushin, get over here you greasemonkeys, I have great news.’ And then he told us the lab had finally worked out the physics of a combat-grade laser, and they were ready for the prototype stage. He pointed at the pile of scrap metal he'd been using as a table for the wine, and he said this new diamond laser could go through it like butter. We were so excited; we had a working model constructed by the end of the day."

- Maria Iglesias, Ph.D, Senior Technician.

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