I am trying to filter out certain wavelengths of light and I was wondering if there is a way that you can filter them out. I am using Silicon Photomultipliers (Linked below) and I only want to detect 830nm, not 400nm-825nm and 835nm-900nm but I can't find similar sensors who only work at this wavelength. Is there something that I can do to filter these out?




closed as off-topic by Hearth, RoyC, Warren Hill, Finbarr, Bimpelrekkie Apr 29 at 9:08

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    \$\begingroup\$ You need coloured glass filters, dichroic filters, or diffraction grating (mesh) filters. They aren't cheap and difficult to work with. Note some have dependencies on angle of incidence. \$\endgroup\$ – DKNguyen Apr 26 at 15:39
  • \$\begingroup\$ Thanks, I will look into them now \$\endgroup\$ – James Apr 26 at 15:40
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    \$\begingroup\$ Dichroic is the most customizable with sharpest cutoffs.. Not dependent on available materials but has an incidence dependency. \$\endgroup\$ – DKNguyen Apr 26 at 15:41
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    \$\begingroup\$ @James Look for "830nm CWL, 10nm FWHM" (or 5nm FWHM if you need it) bandpass interference filters. Be aware that there will be ripple in the bandpass region and that the attenuation in the passband may vary somewhat from one to the next that you buy. Check their specs on the passband and stopbands and whatever else you care about, closely. \$\endgroup\$ – jonk Apr 26 at 16:20
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    \$\begingroup\$ I'm voting to close this question as off-topic because it's a question about optics, not EE. \$\endgroup\$ – Hearth Apr 26 at 17:48

There are plenty of companies that make optical filters in many different wavelengths, look for infrared optical filters. Some companies also sell these in sheets that can be cut to size. Realize that not all filters have 100% transmistivity in the passband (the part of the spectrum the filter allows to pass through).

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    \$\begingroup\$ They also won't absolutely 100% block light in their stop band, which may be an issue when you're using a detector intended for single-photon detection. OP, if you're doing a fluorescence measurement, you may need to do time-domain gating as well as optical filtering to avoid the pump signal overwhelming the fluorescence signal. \$\endgroup\$ – The Photon Apr 26 at 16:08

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