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Thread: Building DPSS from scratch. Trouble getting YV04 to produce any spontaneous emission

  1. #11
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
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    CHECK YOUR PMs before tearing it apart.




    UOTE=brianpe;357140]Wow, 3D Photonics has a lot of really good stuff...with specs too so you know what you're getting. I definitely see some useful things there that could save me a bundle. And thanks for the tips for the IR camera.

    Here is a close-up of the resonator. There are a total of eight mirrors and this photo also shows the beam path. There is more off to the right but it is just steering mirrors and beam shaping optics (all outside the cavity).

    Attachment 58064

    I'm going to abandon getting this head working and just take ideas and possibly parts from it. I'm thinking of an L-Fold design on an optical breadboard like this:

    Attachment 58065
    I should have much better control of the pump waist. This diagram shows an eventual change to SHG but I plan to start with just IR and a 80% OC for 1064 and then add the KTP later.[/QUOTE]
    Qui habet Christos, habet Vitam!
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  2. #12
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    Ah, one of the old spectra physics heads, we used them at work. They just discontinued them.

    You can recalibrate your spectrometer if you have a source of distinct spectral lines like an argon laser or a mercury-argon lamp. You create a spreadsheet of wavelength peaks and ccd pixel location and do some math and it gives you the numbers you need to enter into the software to calibrate it.

  3. #13
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    Default How to focus a multimode fiber into Vanadate?

    Ok, so I did a couple of things as a follow up on my last post:

    1. I tried (and failed) to remove the Nd:YV04 crystal from the Spectra Physics head.
    2. I built my proposed diagram on an optical breadboard.

    The Nd:YV04 crystal looks like it is held in with some melted Indium foil. So I heated up the assembly to just past Indium's melting point and tried to get the holder to separate. It didn't...so I heated it more....and I damaged the anti-reflection coating on the crystal. It's now cloudy. I put it back in the head..and walked away slowly. That was unfortunate as it was the only part of this laser head I planned to retain long term.

    New crystal in hand (only 8mm and now .5% Nd, but I got a bargain on it) I decided to soldier on and lay out my design on an optical breadboard. I've attached an image with the relevant components labeled:

    Click image for larger version. 

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    And now, along with some rudimentary optical equations I pulled from a paper on Newport.com, I think I can see the issue I was originally having.

    The pump diode I'm using is a Coherent FAP. This is fiber coupled and the recommended fiber is 800um multimode with an NA of .16. I'm feeding this into a collimator, and then out of the collimator I'm passing it through a PCX lens to focus it on, or just into, the Vanadate. If I do the math, I find that the output of the collimator should be about 4.88mm in diameter. That matches what I measure and is within the clear aperture reported by Edmund Optics. But the divergence is a whopping 26mRad, and when I plug this back in I find that the smallest dot I can expect from the PCX lens is 2.8mm (also, unfortunately, verified by me). I'm never going to get a population inversion with that. The spot size gets smaller if I decrease the focal length of the lens, but the shortest focal length I can use with "off the shelf" breadboard components is about 40mm, and that still yields a spot size of 2mm.

    I think the fiber size / NA was also the thing that was causing my collimator on the Spectra Physics to not produce a tiny spot. The Spectra Physics head is more closely packed, and I was able to get a smaller spot there because I could use a shorter focal length, but still not dense enough I suspect.

    I considered a beam expander / telescope here, but the divergence gets worse when the beam gets smaller, so I am not sure that will help with anything.

    Anyone have ideas on how best to do this?

    Thanks..Still learning.

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