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  • Ultra fast optical shutter for parabolic concentrator

    From Lucile@21:1/5 to All on Fri Jan 20 09:19:00 2023
    Hello,

    I am currently a PhD student at PROMES-CNRS and in the framework of my thesis I am working on small solar concentrators, to concentrate light up to 10 000 times in an optical fibre. To carry out the planned experiments we would need flashing illumination
    with the whole solar spectrum (wavelength from 350nm to 2500nm). So, we’re looking for a shutter capable of performing this task, ideally with shutter opening times ranging from the ns to the ms timescale. The shutter could be placed either on top of
    the concentrator (option 1), either between the secondary mirror and the optical fibre (option 2), please refer to the following figure. Please note that in position 2 the shutter would be stressed, part of it would be exposed to very high illumination
    levels, which may raise additional mechanical issues.

    The parabolic concentrator's diameter is approximatively 10 cm and the distance between the optical fibre and the secondary mirror is approximatively 5 mm.


    Do you have any ideas where I could find this kind of products?
    Thank you in advance.

    Sincerely,

    Lucile Marechal

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  • From Phil Hobbs@21:1/5 to Lucile on Fri Jan 20 16:12:46 2023
    Lucile wrote:
    Hello,

    I am currently a PhD student at PROMES-CNRS and in the framework of
    my thesis I am working on small solar concentrators, to concentrate
    light up to 10 000 times in an optical fibre. To carry out the
    planned experiments we would need flashing illumination with the
    whole solar spectrum (wavelength from 350nm to 2500nm). So, we’re
    looking for a shutter capable of performing this task, ideally with
    shutter opening times ranging from the ns to the ms timescale. The
    shutter could be placed either on top of the concentrator (option 1),
    either between the secondary mirror and the optical fibre (option 2),
    please refer to the following figure. Please note that in position 2
    the shutter would be stressed, part of it would be exposed to very
    high illumination levels, which may raise additional mechanical
    issues.

    The parabolic concentrator's diameter is approximatively 10 cm and
    the distance between the optical fibre and the secondary mirror is approximatively 5 mm.


    Do you have any ideas where I could find this kind of products? Thank
    you in advance.

    Sincerely,

    Lucile Marechal


    For milliseconds, an LCD would probably get my vote, because of its
    extremely high damage threshold. Being a polarization device, it'll
    lose half your light, but large apertures are available at fairly low
    cost, so it wouldn't have to go right at the fiber. That'll help with
    the damage issue as well.

    I'd probably want to use a walkoff-plate polarizer at the fiber end, so
    that the light can be dumped into something nice and durable.

    Since at 10,000x the NA of sunlight is about 0.44, I gather that you're
    using a high-NA multimode fiber.

    Unless the fiber is really big, you surely aren't talking about that big
    a concentrator--with a 100/125 um fiber, 10,000x only needs an input
    area of 10 mm diameter.

    Cheers

    Phil Hobbs


    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From bob prohaska@21:1/5 to Lucile on Sun Jan 22 23:32:33 2023
    Lucile <[email protected]> wrote:
    Hello,

    I am currently a PhD student at PROMES-CNRS and in the framework of my thesis I am working on small solar concentrators, to concentrate light up to 10 000 times in an optical fibre. To carry out the planned experiments we would need flashing
    illumination with the whole solar spectrum (wavelength from 350nm to 2500nm). So, we?re looking for a shutter capable of performing this task, ideally with shutter opening times ranging from the ns to the ms timescale. The shutter could be placed either
    on top of the concentrator (option 1), either between the secondary mirror and the optical fibre (option 2), please refer to the following figure. Please note that in position 2 the shutter would be stressed, part of it would be exposed to very high
    illumination levels, which may raise additional mechanical issues.

    The parabolic concentrator's diameter is approximatively 10 cm and the distance between the optical fibre and the secondary mirror is approximatively 5 mm.


    Do you have any ideas where I could find this kind of products?


    For nanoseconds, no idea. For milliseconds mechanical choppers might
    work. Probably need two or three in series, to exploit beats and get
    a low enough rep rate with short enough open time. Putting a reflective
    coating on the hot side of the first wheel would help some with the
    thermal loading problem.

    Hope this helps,

    bob prohaska

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  • From Dieter Michel@21:1/5 to All on Tue Feb 7 00:44:28 2023
    Hi Lucile,

    [... whole solar spectrum ...] So, we’re looking for a shutter
    capable of performing this task, ideally with shutter opening
    times ranging from the ns to the ms timescale.

    I don't know about how flexible the geometry of your
    concentrator is, but may a digital micromirror device (DMD)
    be an option for your application?

    I presume that it would be able to switch faster than an LCD
    although I fear that nanoseconds would not be possible.

    There are DMDs that are designed for higher illumination
    levels as e.g. in high-lumen projectors. For your
    application, you wouldn't need the high resolution
    but use all micromirrors simultaneously. I'm almost not
    into the details of DMD design but that might also affect
    the maximum switching frequency.

    A starting point to check whether a DMD-based switch would
    be feasible at all, could be:

    https://www.ti.com/dlp-chip/overview.html


    All the best for your project,

    Dieter

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  • From HoloLab@21:1/5 to All on Tue Feb 14 01:30:31 2023
    A pockels cell?
    Your light source would however need to be polarized and have a reasonably low finesse I think

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  • From Spencer@21:1/5 to Lucile on Sat Feb 25 15:51:40 2023
    On Friday, January 20, 2023 at 12:19:02 PM UTC-5, Lucile wrote:
    Hello,

    I am currently a PhD student at PROMES-CNRS and in the framework of my thesis I am working on small solar concentrators, to concentrate light up to 10 000 times in an optical fibre. To carry out the planned experiments we would need flashing
    illumination with the whole solar spectrum (wavelength from 350nm to 2500nm). So, we’re looking for a shutter capable of performing this task, ideally with shutter opening times ranging from the ns to the ms timescale. The shutter could be placed
    either on top of the concentrator (option 1), either between the secondary mirror and the optical fibre (option 2), please refer to the following figure. Please note that in position 2 the shutter would be stressed, part of it would be exposed to very
    high illumination levels, which may raise additional mechanical issues.

    The parabolic concentrator's diameter is approximatively 10 cm and the distance between the optical fibre and the secondary mirror is approximatively 5 mm.


    Do you have any ideas where I could find this kind of products?
    Thank you in advance.

    Sincerely,

    Lucile Marechal

    Hi Lucile,

    Check this note from a former colleague.. https://arxiv.org/abs/1509.01566 "Fast Compact Laser Shutter Using a Direct Current Motor and 3D Printing"

    They might have posted the CAD file for the shutter and the PN for the motor somewhere, but if you can't find it and are interested let me know, I'll ask them for it.

    Best of luck,
    Spencer

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