Narrow bandpass reflective optical filter

Abstract

A narrow passband, reflective optical filter at a wavelength L, has a container filled with a pressurized gas, the pressurized gas having a ground state transition corresponding to the wavelength L and transparent to all other wavelengths. The container has at least one optically transparent major planar surface serving as the face thereof, whereby incoming broadband light is absorbed by the gas, except at its resonance wavelength L, which is specularly reflected. The optically transparent face of the container optionally has a broadband anti-reflective coating to improve its out-of-band rejection of unwanted wavelengths of the light signal. An optical system utilizing this narrow passband, reflective optical filter has at least one optical element to focus incoming broadband optical signals on the optically transparent face of the narrow passband, reflective optical filter and an optical signal detection component positioned to detect reflected narrowband light of wavelength L specularly reflected from the filter. An optical imaging system utilizing this narrow passband, reflective optical filter has at least one narrow passband, reflective optical filter, at least one optical element to focus incoming broadband optical signals on the optically transparent face of the filter, and an imaging optical signal detection component positioned to detect and view reflected narrowband light of wavelength L specularly reflected from the filter, thereby providing an image of the source of the optical signals.