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Thread: Laser media frequencies

  1. #71
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    Going to don my OD7 goggles

  2. #72
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    ... I have a very similar thread in a German laser-forum - it seems, there is a global demand for such "developments" rising

    Viktor
    Aufruf zum Projekt "Müll-freie Meere" - https://reprap.org/forum/list.php?426
    Call for the project "garbage-free seas" - https://reprap.org/forum/list.php?425

  3. #73
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    I'm wondering what discussion about this fantasy project is doing in the "Advanced Technical Discussions" section? Wouldn't "The Lounge" be better suited for it? Or, as it turns out, "The Dump"? I'd put it right next to those asking for help building a light saber, or resources and materials to make an internal combustion engine, starting with casting a ceramic block. I'm also sad for our friend here. The kind of overconfidence in one's own abilities demonstrated here (and previously at LPF) isn't good for the longevity of pilots.

  4. #74
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    Quote Originally Posted by Eidetic View Post
    I'm wondering what discussion about this fantasy project is doing in the "Advanced Technical Discussions" section? Wouldn't "The Lounge" be better suited for it? Or, as it turns out, "The Dump"? I'd put it right next to those asking for help building a light saber, or resources and materials to make an internal combustion engine, starting with casting a ceramic block. I'm also sad for our friend here. The kind of overconfidence in one's own abilities demonstrated here (and previously at LPF) isn't good for the longevity of pilots.
    I have thought about how lycoming motors could be made from scratch as they do screw people to death on their price point because they have a near monopoly. With the experimental market growing I hope someone starts making the same engine, it’s basicly 1940’s tech so there are not even patent issues.

    The existence of the FAA in small aircraft market give these companies monopoly power because they only certify the companies they want to certify. For some reason this behavior has become normalized.

    I know of no other fed agency that has so much influence over price points as the FAA does.

    I would not be sad if there scope was limited to passenger carrying planes with more that 6-10 people.

  5. #75
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    To the Ar vs As controversy, I'd say that on any other forum people would have written it off as a typo, but given that earlier in the thread we were discussing gas lasers and that Argon is a very common lasing medium I think it's understandable that people thought you really did mean Argon. No harm no foul though.

    Quote Originally Posted by akmetal View Post
    I already found the ND YAG crystals I am just looking for the semi conductor material and dopants now. I need the right P and N type materials to lase in the absorption band of ND YAG.
    Ah, I think you may be confusing two very different technologies here. Let's back up a bit:

    YAG (Yittrium-Aluminum-Garnet) is a glass-like substrate that is used in solid lasers which are optically pumped (either by a flashlamp or by a diode array). The "dopant", or impurity that is added to the YAG is the stuff that actually lases. Neodymium is one commonly used dopant; Vanadate is another. Both will lase at 1064 nm (and a bunch of other IR wavelengths as well, though 1064 is the strongest line). The YAG and the dopant are melted in a crucible and a boule is formed around a seed crystal that is inserted and then slowly withdrawn from the molten mixture. That is polished into a rod, which goes into a cavity to be pumped.

    Note, however, that there is only 1 dopant added, and it is incorporated into the YAG crystal lattice as a bunch of interstitial point defects that are more or less evenly distributed throughout the material. Also, the presence of the dopant does not alter the conductivity of the crystal in any meaningful way.

    Conversely, a laser diode is electrically pumped and uses two different dopants to change the base crystal (usually Gallium-Arsenide) into a P-type semi-conductor on one side, and an N-type semi-conductor on the other side. The P-N junction area where the two different types meet is where lasing action takes place. These diodes are made in a molecular deposition vacuum chamber by first building a substrate of GaAs and then masking off parts of the substrate before adding the P-type dopant (to form 1/2 of the diode), then masking the other side before adding the N-type dopant.

    So the crucial difference is that when building a YAG laser crystal you add the material you actually expect to do the lasing (and nothing else), while in a diode laser you need two different materials (only one of which will ultimately be lasing). Thus it doesn't make sense to talk about P and N type dopants with regard to YAG lasers.

    Quote Originally Posted by akmetal View Post
    I will be building the kiln this spring so that I can melt down materials to get the shapes I need.
    The kiln should get you up to the temperatures you need to make your own YAG crystals, and yes, you can experiment with different dopants, but remember that the resulting boule is *not* suitable for lasing. It will need to be ground and polished first. This requires a good bit of lapidary equipment and expertise. (Just a warning.)

    isn't simply stating to go buy something ready made kind of anti climatic?
    Well, yes, it is. But there are some things that are just not worth doing yourself. Case in point: people built their own planes, but they very rarely build their own engines. They buy one off the shelf. What you are describing is akin to someone purchasing a solid block of aluminium and machining their own engine block from scratch. It is technically doable, but it really doesn't offer any benefit over buying the block already machined for you.

    Do they sell diodes that already emit in 1064 nm and can be pumped with 220 volt 50 amp wall outlet without burning up?
    I'm not aware of any direct-injection diodes that lase at 1064 nm. All of the solid lasers that output 1064 nm light are optically-pumped, at least to the best of my knowledge. (This ignores the chemical gas lasers we discussed previously.)

    However, there are several solid medium lasers that output 1064 nm light at very high energy levels. Diode-pumped medical YAGs probably top out at around the 400 watt level for IR at 1064 nm, and I'm sure there are industrial solutions that go higher. These typically run on 208V 3 phase at 30 amps per leg, which is roughly equivalent to your 220 volt single phase at 50 amps example.

    Furthermore, the military has pushed this design up to at least 50KW, based on recent news reports, and I don't think they've reached the limits of the technology yet. So it's conceivable that a dedicated hobbyist could reach multi-KW outputs with proper engineering and quality optics.

    Basically what we're saying is, "Why re-invent the wheel?". Now, if the goal is just to have fun, experiment, and maybe learn more about the underlying physics, then that has value in itself even if you don't hit your target. But if you want to be sure it will work, start with proven technology. You'll get to the finish line faster, for less money.

    Quote Originally Posted by Eidetic View Post
    I'm wondering what discussion about this fantasy project is doing in the "Advanced Technical Discussions" section? Wouldn't "The Lounge" be better suited for it?
    Some of the replies in this thread have been quite technical. Remember that threads are forever. Someone down the line may be thinking about a similar approach, and if they find this thread they might learn something from what we are discussing today.

    I'd put it right next to those asking for help building a light saber
    And yet there are lots of people who would be interested in such a thing. I think there is value in explaining why a light saber (as depicted in the movies) is not possible. Sure, some people will tune out as soon as they learn it's pure fantasy. But some people will stick around to learn about *why* it's not possible, and even stick around to learn about other things that could be done. Those people are the next generation of laser enthusiasts.

    Quote Originally Posted by akmetal View Post
    I have thought about how lycoming motors could be made from scratch as they do screw people to death on their price point because they have a near monopoly.
    And yet no one has taken up the challenge. Lycoming engines are pricey, but they don't sell nearly as many engines as GM does either. Then there's the liability issue with anything that is flight-rated.

    I think the only way it would work is if someone had access to a commercial-grade CNC mill (and all the tooling) and there were no cost or time constraints.

    The existence of the FAA in small aircraft market give these companies monopoly power because they only certify the companies they want to certify. For some reason this behavior has become normalized.
    Go back to the 1940's when plane crashes due to mechanical failure were more common and you begin to understand the current regulatory climate surrounding all things aviation. I don't disagree that it's worth having the discussion about monopoly powers in aviation, but you do have to acknowledge that there are sound reasons for the rules we have today. Most of them are written in blood.

    I know of no other fed agency that has so much influence over price points as the FAA does.
    Can't argue with you there.

    Adam

  6. #76
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    Quote Originally Posted by buffo View Post
    To the Ar vs As controversy, I'd say that on any other forum people would have written it off as a typo, but given that earlier in the thread we were discussing gas lasers and that Argon is a very common lasing medium I think it's understandable that people thought you really did mean Argon. No harm no foul though.



    Ah, I think you may be confusing two very different technologies here. Let's back up a bit:

    YAG (Yittrium-Aluminum-Garnet) is a glass-like substrate that is used in solid lasers which are optically pumped (either by a flashlamp or by a diode array). The "dopant", or impurity that is added to the YAG is the stuff that actually lases. Neodymium is one commonly used dopant; Vanadate is another. Both will lase at 1064 nm (and a bunch of other IR wavelengths as well, though 1064 is the strongest line). The YAG and the dopant are melted in a crucible and a boule is formed around a seed crystal that is inserted and then slowly withdrawn from the molten mixture. That is polished into a rod, which goes into a cavity to be pumped.

    Note, however, that there is only 1 dopant added, and it is incorporated into the YAG crystal lattice as a bunch of interstitial point defects that are more or less evenly distributed throughout the material. Also, the presence of the dopant does not alter the conductivity of the crystal in any meaningful way.

    Conversely, a laser diode is electrically pumped and uses two different dopants to change the base crystal (usually Gallium-Arsenide) into a P-type semi-conductor on one side, and an N-type semi-conductor on the other side. The P-N junction area where the two different types meet is where lasing action takes place. These diodes are made in a molecular deposition vacuum chamber by first building a substrate of GaAs and then masking off parts of the substrate before adding the P-type dopant (to form 1/2 of the diode), then masking the other side before adding the N-type dopant.

    So the crucial difference is that when building a YAG laser crystal you add the material you actually expect to do the lasing (and nothing else), while in a diode laser you need two different materials (only one of which will ultimately be lasing). Thus it doesn't make sense to talk about P and N type dopants with regard to YAG lasers.



    The kiln should get you up to the temperatures you need to make your own YAG crystals, and yes, you can experiment with different dopants, but remember that the resulting boule is *not* suitable for lasing. It will need to be ground and polished first. This requires a good bit of lapidary equipment and expertise. (Just a warning.)



    Well, yes, it is. But there are some things that are just not worth doing yourself. Case in point: people built their own planes, but they very rarely build their own engines. They buy one off the shelf. What you are describing is akin to someone purchasing a solid block of aluminium and machining their own engine block from scratch. It is technically doable, but it really doesn't offer any benefit over buying the block already machined for you.



    I'm not aware of any direct-injection diodes that lase at 1064 nm. All of the solid lasers that output 1064 nm light are optically-pumped, at least to the best of my knowledge. (This ignores the chemical gas lasers we discussed previously.)

    However, there are several solid medium lasers that output 1064 nm light at very high energy levels. Diode-pumped medical YAGs probably top out at around the 400 watt level for IR at 1064 nm, and I'm sure there are industrial solutions that go higher. These typically run on 208V 3 phase at 30 amps per leg, which is roughly equivalent to your 220 volt single phase at 50 amps example.

    Furthermore, the military has pushed this design up to at least 50KW, based on recent news reports, and I don't think they've reached the limits of the technology yet. So it's conceivable that a dedicated hobbyist could reach multi-KW outputs with proper engineering and quality optics.

    Basically what we're saying is, "Why re-invent the wheel?". Now, if the goal is just to have fun, experiment, and maybe learn more about the underlying physics, then that has value in itself even if you don't hit your target. But if you want to be sure it will work, start with proven technology. You'll get to the finish line faster, for less money.



    Some of the replies in this thread have been quite technical. Remember that threads are forever. Someone down the line may be thinking about a similar approach, and if they find this thread they might learn something from what we are discussing today.



    And yet there are lots of people who would be interested in such a thing. I think there is value in explaining why a light saber (as depicted in the movies) is not possible. Sure, some people will tune out as soon as they learn it's pure fantasy. But some people will stick around to learn about *why* it's not possible, and even stick around to learn about other things that could be done. Those people are the next generation of laser enthusiasts.



    And yet no one has taken up the challenge. Lycoming engines are pricey, but they don't sell nearly as many engines as GM does either. Then there's the liability issue with anything that is flight-rated.

    I think the only way it would work is if someone had access to a commercial-grade CNC mill (and all the tooling) and there were no cost or time constraints.



    Go back to the 1940's when plane crashes due to mechanical failure were more common and you begin to understand the current regulatory climate surrounding all things aviation. I don't disagree that it's worth having the discussion about monopoly powers in aviation, but you do have to acknowledge that there are sound reasons for the rules we have today. Most of them are written in blood.



    Can't argue with you there.

    Adam
    A commercial CNC set up would be cool, There is a little company here that has a HAAS and could probably machine out an engine for you but the machine time would be costly and its not just the block there are all the lifters, valves and accessorys ran off the cam through gears. Its hard to get killed in a plane wreck if you are too broke to comply with all the regulations as you wont be in the air in the first place. When I was in my old job as a process engineer we had all kinds of safety meetings and as a staunch process safety guy myself its VERY possible to go way over the top and we would joke that the safest thing to do was to not build a plant at all.

    I think this is why we are seeing a surge in experimental category and light sport, people want to fly and they should be able to take the risk without being millionares. Dont we tout risk taking as americans?

    Monopoly (or even oligopoly powers since continental technically exists though is too heavy for aerobatic applications) power should have no place in american society yet its pretty much all our society is now. Pick any industry and you can probably only point to maybe 6 major players (aviation is probably the worst, I mean there are only 3 companies that make turbines and one is foreign). So much so that I am having to order parts and equipment over seas which I hate doing but it seems the Russians and Chineese are less greedy than americans. $1950 for one MoSi2 heating element ... I think not.

  7. #77
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    Quote Originally Posted by akmetal View Post
    Its hard to get killed in a plane wreck if you are too broke to comply with all the regulations as you wont be in the air in the first place.
    That's true!

    When I was in my old job as a process engineer we had all kinds of safety meetings and as a staunch process safety guy myself its VERY possible to go way over the top and we would joke that the safest thing to do was to not build a plant at all.
    In a nutshell, "Safety Third". (With apologies to Mike Rowe.)

    I think this is why we are seeing a surge in experimental category and light sport, people want to fly and they should be able to take the risk without being millionares.
    Right. Those categories have almost no restrictions on engines, correct? So if I want to build a light sport that is powered by a lawnmower engine, I can do so? (Not that I think this is a good idea, mind you, but just that it is technically possible and legally allowed.)

    I draw the line when one person's right to innovate puts others at risk. So carrying any paying passengers is out for an experimental craft, as is flying over congested areas (where a crash might reasonably be expected to harm people on the ground). Beyond that though, I'm OK with someone building their own plane and crashing it if they goofed the design.

    Adam

  8. #78
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    Found some ND: YAG rods to get me started. Books are all in and I am spending a lot of time reading.
    Attached Thumbnails Attached Thumbnails rods.JPG  


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