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Thread: 1342nm DPSS Laser

  1. #1
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    Default 1342nm DPSS Laser

    Got another new toy, another chinese prototype laser head, looks like a copy of a Lightwave M110 head. Though this guy puts out 1342nm. It is pumped with a little 5w 808nm Spectra Physics fiber coupled diode, a SFA200-808-Z5-01A (http://www.oclaro.com/product_pages/..._SF_Series.php) The diode itself sits on a couple pelters and the fiber is fed to a lens and mirror to end pump a vandanate crystal with a little q-switch in the cavity.

    The basic construction is no bad quality. Though the little interface board has some awful soldering. I managed to clean some of it up.

    I powered it up with my 1U rack mount supply from Electronic Measurements Inc, it is very stable and well behaved, had to use this since my real diode supplies dont go this high (7 amps)

    It seems like it works. I need to figure out what the resonant frequency of the q-switch is. There are no markings on the switch or the unit. Hopefully it will be 40.68MHz, I have a couple drivers that would work great. The path the beam takes though the crystal is kind of offset. Is this to polarize the beam>

    Here are some pics of it including one pic taken with my IR modified dSLR.


    Chinese 1342nm DPSS Laser by macona, on Flickr


    Chinese 1342nm DPSS Laser by macona, on Flickr


    Chinese 1342nm DPSS Laser by macona, on Flickr


    Chinese 1342nm DPSS Laser by macona, on Flickr


    Chinese 1342nm DPSS Laser by macona, on Flickr

  2. #2
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    If you mix the Q-switched output in the proper crystal with 1064, I did the quick math and came out with something between 590 and 600...
    Doubled of course is 671... That 1342 wavelength would be nice for micromachining polymers...

    Edit, I ran the math... product would be 593...

    You'd need angles Theta at 43 degrees and Phi at Zero in KTP



    Steve
    Last edited by mixedgas; 12-01-2012 at 04:14.

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    I like this little unit. Could you review the optical path? I'm having a little trouble with what looks like a knife edge clamped after the Q switch as well as the crystals that seem a little isolated and contacting the aluminum plate further yet from the Q switch.

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    In the last pic you can see a grey block that the fiber feeds into, this collimates and focuses the diodes's light onto the crystal via the mirror on the corner. I am assuming the crystal is coated HT808 and HR1342 on it's rear face. In the third pic you can see the entire resonator. The part between the q-switch and the OC is a aperture plate. This limit's the beam diameter and also helps keep the beam TEM00, or so I have been told. It is just a piece of copper with a small (~1mm) hole in the middle. The aluminum box this all fits in to has a IR filter on the output aperture, I assume to filter out stray 808nm light from the diode.

    Steve, is there a good source explaining theta and phi regarding NLO's? Or might that be on this forum already?

  5. #5
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    As for NLO, the definitive simple book is by Amon Yariv ... Helps if you have some high end algebra or calc... I dont have calc, so

    I'll have to send you something... Phase matching of (type 1, type 2 and type 0) SHG is beyond the scope of what I have time to type. There is also some software I can send you a link to. PM sent.

    Frequency doubling is "roughly" summing of photons using a electron as a parametric oscillator. Parametric is a bit different from the "Simple Harmonic" oscillator they teach you about. I know what it is when I see it, but expaining it in a short paragraph is something else...

    A horrible analogy:

    Think of it as a long metal pendulum with a hinge built into its shaft ..... A hinge that can be anywhere along the pendulum... And each part of the pendulum can be driven independently. What the "BOB" at the end does is whats important... And is the vector sum of its motions...

    Its not quite what a frequency doubler does in practical electronics, its more of a mixer.

    Steve
    Last edited by mixedgas; 12-03-2012 at 12:53.

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    OK, I think I understand, a bit...

    Here is another 1342nm head I got. This one is externally pumped from a remote power supply and q-switch driver. The head is an engineering sample. I am nut sure if it even went into production. It does have a pretty good sized crystal. How many watts can you push in a crystal before you need active cooling?


    Spectra Physics 1342nm DPSS Head by macona, on Flickr


    Spectra Physics 1342nm DPSS Head by macona, on Flickr

  7. #7
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    I found the original power supply for the chinese head. Unfortunately someone scavenged some parts out it, namely the 24v power supply and the Q-switch driver. 24v is easy. From the interface, power supply connections, and mounting pattern for the driver I managed to figure out it is a NEOS 39000 series Q-Switch driver.

    http://www.neostech.com/PDFs/Asize/56/56A17161.pdf

    There are only 4 frequencies these are available in so that at leasts narrows it down to what the crystal is.

    But it works without the rf driver in it. I get about 1 watt CW at 5 amps diode current (maximum for power supply) I have not tried adjusting the TEC temp to see if I get better efficiency. The power supply says it has only 193 hours emission time on it.


    DPSS power supply by macona, on Flickr

    -Jerry

  8. #8
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    Quote Originally Posted by macona View Post
    It does have a pretty good sized crystal. How many watts can you push in a crystal before you need active cooling?
    Depends on thermal properties of the crystal ie specific heat, coefficients for thermal lensing/expansion, the pumping technique, and the geometry/relative dimensions of the crystal. You learn this by knowing what the crystal is. Vandate vs YAG, LBO vs BBO etc.


  9. #9
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    Found out that those 1.3u heads I have are a chinese knock-off of a Lightwave M112 system. There is almost no info on these. My friend got a couple heads and the matching power supplies and I tested them for him. I popped one open to see what was inside and found a near identical setup with the same q-switch. I opened one of the power supplies and the q-switch driver is 108.48Mhz, right where the VNA dipped at. So now I know what frequency I need.

    Here is a pic of the head, sorry, no real detail. I was just trying to pick up any IR but it seems my 5DII has a very good IR cut filter. The diode is putting out but there is no 1.3u as far as I can tell.


    IMG_5293 by macona, on Flickr

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