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Thread: Red diode setup?

  1. #11
    Join Date
    May 2009


    am I missing something, why would you need both prisms and c-lenses?

  2. #12
    Join Date
    Oct 2007
    Vancouver, Canada


    I was wondering the same thing, was going to ask earlier but was too early in the morning and lost track of this thread

    It seems to be the resulting beam would be too wide to fit scanner mirrors after double expansion..

  3. #13
    Join Date
    Jun 2012


    Thanks for the response planters! I have the deepest of respect for your work!

    First of this is not my first laser module i have done some 8 w blues without correction and so on so this seems to be the next step for me hehe
    make some real pretty beams instead hehe

    And yes as you can see i have changed the last diagrams so the bottom pair is shifted to the right and i will make sure to make the distance the same when it comes to the acctual build

    I think i get the last part of your suggestions as well that if i knife after the correction i will have sqaure beams and not the stribe to to knife with but i dont know what you mean with it being missalign more then if i knife were the pbs if know?

    The reson of the prism pair if only a theory that if i use them after the knife so that i could maybe correct the knifeedgeing to be sqaure again hehe but i dont know if it can do that to the extend where it makes sense to do it hehe

    Just to get one thing stright hehe i have done my reserch but i am quite unsure about everything untill i get a final YES to something

    The convex / concave correction "folds" the beam in to form a sqaure - slow down the fast axis and needs to be not to far and not to close the the diodes to get the best mrad / size compensation right?

    The prism pair is a beam expantion correction to speed up the slow axis of the diode? Right? Or can they be used the other way as well to slow down the fast axis?
    And dose the pair need to have the same distance to the diodes? And if they do how come youre big 2d set up blue works planters? Haha

    What i still dont understand is that if the prism pair is af beam expansion correction why use it? And why use that on the blue but the 2d lenses on the red? Hehe
    My goal is to get the most amont of ligt out as small as possible with the best divergense as possible hehe (arent we all) but i dont care if the blue is smaller than the red and so on just that each have the best specs possible haha
    And yea i am willing to build the big 8 diode setup !

    And last a stray ideer..
    Could you knife within a focus point like where you cut the mulimode stripes away? Ofc. the distance and so on needs to be just right and it would be a pain working with.. but, you would be able to use the knifeedgeing mirror to cut away multimode stripes as well and realy see where you are with your knife hehe

    Sorry for my gramma ond spelling.. its not my strong side so bear with me!
    Last edited by SimonNeve; 11-17-2013 at 17:24.

  4. #14
    Join Date
    Feb 2011
    New Hampshire



    Your post is long and contains many questions and ideas. Rather than try to discuss everything in one response let me pick out a few now and come back to the rest later.

    I do not want to use the term fast and slow to describe the divergence. I prefer to use the idea of a beam product. The smaller the product of a given dimension of the beam multiplied by its divergence the better the beam. This product is has a minimum for each laser and for each axis ie horizontal vs vertical. It has no maximum if aberrations such as defocus or off-axis coma is introduced. When a lens pair or a prism(s) are used they simply expand the beam dimension near the laser and if no aberrations are introduced they cause an inverse and proportional decrease in the divergence. When using a lens pair to expand more than a single diode stripe the outboard stripes suffer off axis spherical aberration (a defocusing) and coma (a curving distortion). The further outboard you go the worse the problem. My reds are stacked vertically in the vertical cylinders and therefore are all on axis. The blues are expanded with a prism pair and here there are no off axis aberrations, but light loss can become a problem with higher expansion ratios (say 3 and above). But again here, because I have so many diodes I can only expand about 2 times.

    Knife edging REALLY WELL is VERY HARD. You are trying to free-hand-slide a tiny optical component with its hold down screw just loose enough to allow it to move, but not too loose and a movement of as little as 100um makes a significant difference. The edge of the knife (best a prism) needs to be parallel to the stripe to a fraction of a degree. Otherwise, you will have too big a gap at one end or cut off light at the other. You can knife edge after the beam expansion. This actually eases the tolerances and will work better, but it will probably be less optimal to knife edge a pair of thin PBS overlayed stripes because the overlay will probably not be precise enough to allow as clean a packing.

  5. #15
    Join Date
    Nov 2008
    Cleveland Ohio


    not to mention you will need a waveplate to rotate one of the diodes so they both line up after the pbs like || Otherwise you can't knife edge it at all.

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