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Thread: Frequency doubling into the yellow

  1. #51
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    I, too, am sill looking for a decent yellow. 50mW would be fine for my single-mode projectors. I'd even go for $200 a pop! Anything in the 570 range would be perfect.
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    Quote Originally Posted by absolom7691 View Post
    I, too, am sill looking for a decent yellow. 50mW would be fine for my single-mode projectors. I'd even go for $200 a pop! Anything in the 570 range would be perfect.
    Agreed. Every once and a while we get a taste of something that turns out to be a once-off (like 473nm single mode diodes that do 80mw) or stuff that readily dies like the cheap frequency doubling yellows. It's a bummer when it doesn't work out, but we have gotten mega-loads of direct blue, 520nm single and multimodes and good 405nm diodes over the past decade, so I suppose I can't complain too much.

    -David
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  3. #53
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    ... when testing the shielding capacity of blue 445nm and UV 405nm laserdiodes through orange-coloured "UV-blocking" acrylic, I've notized, that the blue laser beam was complete blocked, but some "orange" light was wisible on a spot behind the window -- could this be some sort of fluorescency or "secondary emission", something like pumping disk-lasers?

    Then maybe you can get some pure orange or yellow light by blocking the blue/UV after a disk with the proper dye to get some fluorescency through? - woud be a bummer!!

    Viktor
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  4. #54
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    The material melts at just below 2100'C and must be worked under inert gas while growing. The seed crystal must be spun and slowly withdrawn from the melt over a period of months. Practical home heating elements stop at 1200'C.

    It is not a candidate for either Verneuil Furnace nor Hydrothermal growth. I don't know where an Amateur would get the budget for massive platinum crucibles, either. Once you have it, you have to orient and cut it using a X-ray crystallography machine. Really strictly industrial.

    I spent a lot of time at lunch last year trying to come up with a durable low temperature glass that an undergraduate student can make using an oven at 900'C. That was difficult, and the requirements for NO toxic or neurotoxic (Lead Oxide) materials in the project made it even more so. Most of the fining agents for removing the bubbles formed in the melt are incredibly toxic in the fumes they release. I can tell you this, getting neodymium oxide to melt and distribute itself was not easy, even with an aggressive fluoride flux in the mix.

    The way you make it head towards an optical grade piece of glass is to quench it , crush it, and re-melt it multiple times. That required incredible patience and large amounts of fuel gas and oxygen to get even close to house window grade glass with a thin piece. Not easy... Got it working really well with the Lead Oxide in the batch, however. AT 1100'C, the lead free mix was slowly dissolving the alumina in the crucibles.

    The professors, and rightfully so, did not want to risk exposure of future young mothers to the lead. Most of the alternatives would have needed eight hours melted to really de-bubble. lead based materials de-bubbled in minutes. The problem with lead based glasses for laser is thermal, they simply trap heat and are poor thermal conductors. Which is why glass based laser rods are lead free, high melting Phosphates and Silicates. That still makes them single shot at a time devices. At least I saw Laser Induced Fluorescence with the ND dopant , while hitting it with 808. I just can't see you growing something at 2000'C on a home scale at any reasonable cost, let alone sustain the growth for months.

    I did end up with a recipe for somewhat brittle Blue and Old Gold glass that works, ie the school colors, in 45 minutes plus annealing. Project is shelved as part of new management did not like the idea of undergrads loading ovens for overnight heats. Which is a shame, because glass manufacturing is a wonderful applied process for beginning Chemical Engineers to model.

    Now why did I mention the glass you ask? Because I've tried to cheat already. The oxide in the yellow crystalline material is on order, a few grams, if it makes it through the Russian postal system. The literature says low melting Glass hosts rob it of energy before it can lase, and only fluoride based crystals or exotic fluoride glasses, or lanthanide / fluoride series crystals will host it. No way I could do a Fluoride based melt, not even in a borrowed or rented artistic glassblowing shop. Too dangerous, and I cannot afford the crucible.

    But I'm curious if I can see the 1175 nm stimulated emission or a tiny yellow fluorescence using a 975 nm pump just before my cheap mix cracks from the focused energy. Or if I can get it to dissolve into 7070 series aluminosilicate glass, which I have as a glass powdered frit for artistic glassblowing. Even if it diffuses into the glass, the odds of it being self doubling in an amorphous host are NIL.

    As Kecked rolls his eyes and I join him as we both know I'm wasting my time burning through my remaining pre-mix of a few grams of proto-glass. I have to melt and fuse it anyways so it is safe for disposal.

    BTW, the crystals in the laser we were sold are bluish in transmission, so it will adsorb its own laser emission, too...

    Steve
    Last edited by mixedgas; 07-22-2020 at 17:26.
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    Fascinating, Steve! Absolutely fascinating!

    I did not realize that growing a boule was a month-long process. I assumed that it was something that could be accomplished in a matter of a few hours, or perhaps a single day at most. Clearly, this is not something the average person would ever consider attempting as a DIY project.

    Adam

  6. #56
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    ah damn shame.
    I guess we have to keep hoping for a better 1175nm source to pop up at a better cost or a different break through for yellow.
    Was hoping to spark up the conversation to see if there were any advancements towards the right direction.

  7. #57
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    There is a company in Canada that makes a PPLN orange but it is clipped at about 30 mW. After zillions of pointer folks called them asking about single pieces, they only speak to industry professionals now, who wish to order in the thousands.
    One laser show fellow did get a three device quote and the cost was beyond reasonable. That is just the module, no optics to clean up the beam, no driver etc...

    1121 is doable, I have the optics for it, but the crisis and a continuing senior care crisis keep pulling me off of it. Laser design with the competing 1064 line present means it is not just something I can hand off to another experimenter.



    Steve
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  8. #58
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    Quote Originally Posted by masterpj View Post
    ah damn shame.
    I guess we have to keep hoping for a better 1175nm source to pop up at a better cost or a different break through for yellow.
    Was hoping to spark up the conversation to see if there were any advancements towards the right direction.
    Whatever happened to Chauvet's direct yellow with the same/similar material? Never mind, still on pre-order / pre-release/ back order...

    Steve
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  9. #59
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    There are Sol-Gel methods for making potential rare earth crystal hosts requiring fusion only as a final step. I'll look at the potential just as a hobbyist on my own time, but I doubt anyone is going to ship TEOS to a home lab. Tetraethyl Orthosilicate.

    Steve

    Last edited by mixedgas; 07-24-2020 at 06:27.
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  10. #60
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    ... what's with 405nm DPSS for orange or yellow (like "pumping" dyed acrylics for low powers, so they won't melt) ?

    I have some glass blocks too, which converts UV into "neon" yellow-green ...

    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

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