Ultra fast optical shutter for parabolic concentrator

[Lucile]

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

[Phil Hobbs]

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

[bob prohaska]

Lucile <lucilema...@gmail.com> 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

[Dieter Michel]

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

[HoloLab]

A pockels cell?
Your light source would however need to be polarized and have a reasonably low finesse I think

[Spencer]

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