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Thread: Melles Griot DPSS/Optics Questions

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    Question Melles Griot DPSS/Optics Questions

    Hey all,

    I decided to extract the Melles Griot head and power supply out of my Mobolazer last night, on a whim. I keep toying with the idea of putting it in a new, smaller enclosure so I can bring it on a plane easier and also get the most out of my beam. I figured I should familiarize myself with the optics etc.

    My question, for now, is what the optics, pictured below, are exactly, and if I should put them aside for now or keep them. The way it's currently set up would work pretty well for a smaller enclosure as the beam comes out at a 90 angle which would probably make it easier to achieve a balanced look on the outside of the aforementioned new laser enclosure. (beam window centered etc.)

    I'm still on the fence about blanking also. After much nagging on my part of the nice people at MG, I've determined that I definitely have no useful modulation on the power supply currently paired with the laser.
    Anyone ever heard of after-market or modded MG power supplies? Otherwise, my other two options seem to be an AOM or optical leverage blanking.


    As you can see in the pictures, these optics are adjustable and mounted on rubber grommets to ensure the customer has to regularly bring the unit in for tuning or something. (right?) You may also notice that the pictured optics are mounted directly after the combiner/expander which may need some attention also. I have some pretty specific directions on adjusting the combiner/expander, at least.

    So, to sum up:

    1. What are those optics, exactly?
    2. What's your opinion on AOM vs. Optical Leverage Blanking (I know an AOM would be considerably faster, but I believe I'd lose less light with OL blanking..)
    3. Are the extra optics worthwhile, or are they contributing to beam divergence, power loss or diamond cartels in Africa, perhaps?


    Thanks for reading!

    -Jonathan

    P.S: I threw in a beam shot from last night for additional illustration.
    Attached Thumbnails Attached Thumbnails IMG_7914.JPG  

    IMG_7915.JPG  

    IMG_7916.JPG  

    IMG_7909.JPG  


  2. #2
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    I have no experience with MG lasers, except for the fact that I wanted one forever... but it almost looks as if the PBS cube could be used for laser power output feedback.

    I am sure someone who is more familiar with this particular laser will chime in... but thats just what it appears to be... of course more pictures would help clarify if that was the case.

    As far as optical losses and the benefits of using AOM vs Leverage blanking... I would go with AOM any day over optical... unless you were using a Laserscope or something similar. The speed achievable with an AOM is huge... Optical blanking can be pretty fast too, but you if you have say 4 or 5 mirrors the laser is passing through for the full optical blanking path at even 1% loss that is still a loss...

    Either way you will have losses... you just have to weigh it out... I would go AOM if you have the resources. Hopefully this makes sense I am pretty scatter brained right now after the class I was just in.

  3. #3
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    due to a quirk in the way KTP and other doubling crystals work, sometimes if you want max power from the cavity you get two green beams from a high power Greenie. Its problem called Poynting Vector Walkoff. I'm not going into the physics of that one, save for the laser designer sometimes physics sucks. In your case they have the two beams to get max power.

    What the design team at Laser Power Microlasers (whom Melles bought) did was bring out both beams, shift the polarization of one beam slightly, which accounts for the square waveplate glued to the body, and run it into a polarizing cube via that right angle fold mirror
    to combine them. Some attribute that more compact design you have design to a engineer at Laser Fantasy. LFI bought huge amounts of those lasers and resold them to get the costs down. I met the guy who did most of the LP work, and he was a good designer. He sadly passed away a few years ago. His name was Dean Hodges.

    So you have a waveplate, a P cube , and a fold mirror. I would'nt mess with their alignment, but I would keep them very clean with optics grade methanol and acetone.
    Keep the chems off the mounting RTV-silicon and epoxy. Recently another PL member found out what happens if those optics get burnt.

    Since I have'nt said it here in a while, WATCH YOUR EYES WITH THAT ONE !


    Steve

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    Sadly I dont know enough about optical blanking vs. AOM's so I cant really answer your question, but I do have a question for you!

    Maybe I missed it somewhere, but what is the power rating on that laser?

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    Thanks for the quick responses guys! I was thinking that was a PBS cube. I'll just stick to slightly adjusting the combiner/expander when I get around to bringing this out to a nice large space to get a good beam profile. (I figure I'll bounce off a good mirror 200+ft away and hit my white target board I have -with my 532 glasses on.)

    Quote Originally Posted by mixedgas View Post
    . . .Since I have'nt said it here in a while, WATCH YOUR EYES WITH THAT ONE !

    Steve
    I'll never forget getting this thing running at a camping trip in '06. I didn't get any direct hits while setting it up on top of my Caravan, but it became clear pretty quick that I needed some goggles ASAP.

    Ever since that first summer, I've been paranoid about ocular damage. It took 5-7 RGB lasers at once to get me to voluntarily get in the path of a laser and look in it's general direction. (SELEM balcony extravaganza )

    AOM it is! I have a feeling OL blanking would be a little more tricky and *maybe* more expensive anyway. By the way, any word on the possibility of some sort of AOM group-buy Steve? I remember you mentioned something like that a little while back.


    -Jonathan

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    Quote Originally Posted by GooeyGus View Post
    . . .Maybe I missed it somewhere, but what is the power rating on that laser?

    It's rated 3 Watts max according to the manual, but it's supposed to put out around 2.5, typically. I want to get it tested soon, but I need to find someone near here with a good power meter first.

    -Jonathan

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    Quote Originally Posted by platinum View Post
    It's rated 3 Watts max according to the manual, but it's supposed to put out around 2.5, typically. I want to get it tested soon, but I need to find someone near here with a good power meter first.

    -Jonathan
    I have a Scientech 364 meter if you feel like driving up to marysville. The door is always open for a fellow laserist!!

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    Quote Originally Posted by GooeyGus View Post
    I have a Scientech 364 meter if you feel like driving up to marysville. The door is always open for a fellow laserist!!
    PM sent. Thanks for the offer!

    -Jonathan

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    I wouldn't bother with an aom, I would use a scanner for blanking. Especially if it is just a beam box. Remember that is no longer a polarized beam and some aoms have poor efficacy with out a nice polarized beam.

    just a thought.

    chad


    When the going gets weird, the weird turn pro.


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    [QUOTE=chad;69812]I wouldn't bother with an aom, I would use a scanner for blanking. Especially if it is just a beam box. Remember that is no longer a polarized beam and some aoms have poor efficacy with out a nice polarized beam.

    One thing he could do is two scan heads, more heads = better show.

    Steve

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