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Thread: Sourcing Pr:YLF crystals

  1. #11
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    I have a laser on campus that uses Nd: YLF in wet cooling with the rod submerged and lamp pumped. Its simple, a new rod every about two years because of the slow solubility in DI water. It degrades slowly, except where the strong electric field of the intra-cavity beam hits it. There it will degrade fast from water vapor if not coated. Still it should be kept very dry.

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    Quote Originally Posted by danielbriggs View Post
    Here's a CAD render from a design I made years ago for an experimental cavity for exploring Pr:YLF (482nm, 523nm, 607nm, 640nm) pumped by 445nm (Although the blue and green lines are not worth chasing).

    Hi Daniel,

    Nice set up, did you end up realizing the design? On another note, we're the 482 and 523 lines not worth it for the power yield at those lines?

    Thanks,
    Ash

  3. #13
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    Yes,
    The 482 and 523nm were <10mW for a 1W 445nm pump.
    - There is no such word as "can't" -
    - 60% of the time it works every time -

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    Quote Originally Posted by danielbriggs View Post
    Yes,
    The 482 and 523nm were <10mW for a 1W 445nm pump.
    Wow, what were the specs on the crystal!?

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    Some light reading about the 607nm output as well.

    Highly efficient InGaN-LD-pumped bulk Pr:YLF orange laser at 607 nm
    Only an electron wiggler like you would resonate at 30cm.

  6. #16
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    Soulfeast, the paper you linked calls for a 8 mm long , 0.2% doped crystal.



    Steve
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    Yes it does. I don't expect it to be duplicated, just mentioning it as additional information for this particular crystal. They were also pumping 850mW in a linear cavity and achieving 150-200mW of 607nm with those 8mm. Shaving a mm or two will still have significant results if we play our cards right with the mirrors and all that jazz. See further below for other sourcing on precise crystal and mirror coatings used by ALKAAD.

    ALKAAD - The company that sells an instructional DPSS kit involving 444nm pumped Pr:YLF, using a 0.7% source, and a littrow prism or birefringent filter for tunability along five orange-red lines.
    606, 639, 676, 697, and 720.
    Document found here.
    Website and products here.

    Doping is significant, yes, but let's try to keep something reasonable here. We don't want to burn them, or block too much light.

    Secondly, Northrop Grumman already has 0.2% in stock. The length of the rod will only really affect the gain to an obvious degree that could likely be worked around pending mirrors, input wattage, yada yada.

    Point is, this thing lases at 0.2% and 0.7%, big and small. A little variability doesn't hurt this thing.
    Only an electron wiggler like you would resonate at 30cm.

  8. #18
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    Just remember your optics or an intra-cavity device has to block the lasing of the adsorbing line to get full power.
    YLF suffers from early optical damage, I have a side pumped piece ( ND Doped) at home that has a internal burn every centimeter from five pump diodes that were too tightly focused.

    Steve
    Last edited by mixedgas; 09-15-2016 at 06:44.
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    I'd have them pass 445nm anyway, if not for the crystal, then for the diode. Sending light back onto the die isn't a great idea either.
    Only an electron wiggler like you would resonate at 30cm.

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    The peak absorption of Pr:YLF is 443.8nm.
    Some tips if you want to design for the best possible efficiency + stability (ignore if you just want orange+red light out):

    Modulating the current of GaN diode significantly shifts its emission wavelength (5-10nm in some cases); temperature effects are relatively insignificant (in contrast with red laser diodes).
    So it's best to fix the current at a known point + observe the emission wavelength // tune as close as possible to 443.8nm at around the output power level of the diode. You may want to order a dozen GaN's to hand pick the optimum diode which lases close to the peak absorption, at the operating current. There is a significant manufacturing variation.
    Then modulate the output of the 607/638nm with an AOM.
    As well as providing the best route for efficiency in this manner, it will also iron out most of the thermal stability issues of DPSS lasers.

    Backreflection on GaN diodes, while still a concern, is not as sensitive as it is for red diodes.

    Dan
    - There is no such word as "can't" -
    - 60% of the time it works every time -

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