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Thread: Octo Multimode

  1. #1
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    Default Octo Multimode

    Hi,
    After reading tons of how-to stacking threads (I'm building P73 quad now) I still have not found:

    #1:

    520/445nm multimode: How to combine 8 520nm 1w Nichia for 1mrad or less and 6mm beam or less??

    Going with g2 lens (fl 4mm aprox) for example...

    llll + llll (PBs) + anamorphic prisms?

    #2:

    638nm multimode: Same as above...how to combine 8 500mw p73 for 1mrad or less And 6mm beam or less?

    perhaps:
    f2 colli lens (Dave's):

    :: + :: + cyls? (stacked vertically pair+knife edged another vertically stacked set (4 diodes) all doubled thru PBS)


    Thanks!
    Last edited by jors; 09-19-2018 at 04:13.

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    To begin, there is no method of stacking or combining that will give you a specified beam product if you specify a better divergence and smaller beam than the starting laser can deliver. There is no magic formula either. Dave's lenses or the Optima 4mm lenses will produce the same result. The 4mm will be expanded less later, but with the same end result.

    I say this because your post seams to indicate that you want the best results you can get, but also a specific minimum. These don't go together. I have done a lot of beam manipulation of these diodes and if you do everything right, perfect focus, perfect alignment and lossy knife edging then you might JUST meet those criteria.

    The stacking threads are probably pretty old by now, but if you are building a quad now then the 8 is really not a big leap from there. Once you have finished you can then practically estimate the performance of 8 diodes. The beam area will be twice as large or the divergence twice as great.

    On your 520 example, if you start with llll +llll and overlap them with a PBS then an anamorphic pair will produce a very rectangular beam. I would stack a pair ll above another pair ll the PBS this taller, but narrower arrangement and then the anamorphic prism will broaden this into a square.

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    #1: possible. I would recommend ll over ll pbs ll over ll. Having just done something very similar i would do l over l pbs l over l then correction (X2) then knife edge the two beams. This method will take more optics and more room. If you try all the knifing before the prisms the gap between knifed beams after the prisms will grow in proportion to the expansion. This will limit your near or far field size. It would also be possible to remove the gap between the beams after the prisms with another set of knife edge mirrors.

    #2 Not gonna happen! If you can do 8-9mm scanner mirrors then 1mrad is possible. Aligning a quad is a nightmare. I would do llll pbs llll where the correction is done in the vertical direction. With daves 2mm lenses you can get 8x8 mm with around 1mrad or just under.

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    Thanks guys!

    Logsquared: Which diode collimators do you propose on #1 please?? With G2, NF beam profile out from my greens 1W Nichias is 5mm high (a bit less) for just one diode....so if I stack l over l... the result is 10mm high NF beam profile!! (plus gap between) this is way more then 6mm or less which is desirable.
    so... I could go with Dave's 2mm collis also for greens, but DAve's collis are red AR only so not recommended for greens

    thanks!!
    Jordi

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    Quote Originally Posted by jors View Post
    Thanks guys!

    Logsquared: Which diode collimators do you propose on #1 please?? With G2, NF beam profile out from my greens 1W Nichias is 5mm high (a bit less) for just one diode....so if I stack l over l... the result is 10mm high NF beam profile!! (plus gap between) this is way more then 6mm or less which is desirable.
    so... I could go with Dave's 2mm collis also for greens, but DAve's collis are red AR only so not recommended for greens

    thanks!!
    Jordi
    The beam just looks 5mm tall. In my tests 95% of the power is in the central 3mm. So you can stack 2 in 6mm with out too much loss.

    I have used dave's 2mm on blue with little loss. I would bet they work well with green too.

    In my opinion the benefits of 2mm lenses are: smaller stacked nearfields with OK farfields (<1mrad)

    The cons are: losses are higher if you "cut into" the beam when knife edging. Also, the price is high and adds up with multiple diodes.

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    Many thanks Chris

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    Jors, these are the reds Logsquared was referring to. We'd already spoke about prism correcting the vertical axis, and tonight the prisms arrived from Lasertack, so I tested it and it worked beautifully. These now fit on the mirrors just right.
    I thought we'd be losing a load of power with all of the optics but adding the prisms only took out about 3-4%

    And the prisms seem to work just fine tucked in between the cylinders, its an excellent use of space.

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    Frikkin Lasers
    http://www.frikkinlasers.co.uk

    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

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    Quote Originally Posted by jors View Post
    Thanks for share Adam! this is so smart!

    However, my P73 quad beam fits on PT-A40 (5mm), so why those prisms?
    As you can see below pic, there is no red looses on galvos.
    Yes, you shrink beam height so there's more power density ie brightness beam, but...on the other side... if beam is smaller due prisms at NF, spot at FF should be bigger, cause you are increasing beam divergence, optics laws applies here.
    So...higher brightness near projector, but less brightness far from PJ due a higher divergence...isn't it?
    Attachment 47560
    jors -

    that is a beautiful bit of work! do you have any interest in selling modules or kits?
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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    Quote Originally Posted by jors View Post
    Thanks for share Adam! this is so smart!

    However, my P73 quad beam fits on PT-A40 (5mm), so why those prisms?
    As you can see below pic, there is no red looses on galvos.
    Yes, you shrink beam height so there's more power density ie brightness beam, but...on the other side... if beam is smaller due prisms at NF, spot at FF should be bigger, cause you are increasing beam divergence, optics laws applies here.
    So...higher brightness near projector, but less brightness far from PJ due a higher divergence...isn't it?
    Attachment 47560
    We used 4mm collimators on that build.

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    Many thanks Swami
    yes, I've invested tons of hours, money and effort on developing. I'll post on "Selling" here on PL soon. fingers crossed!

    Quote Originally Posted by swamidog View Post
    jors -

    that is a beautiful bit of work! do you have any interest in selling modules or kits?

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