A volume holographic grating is formed by writing an interference pattern into a thick material using two beams of light, known as an object beam and a reference beam. Once the grating is formed, if it is illuminated with either one of the write beams at the correct wavelength, the second beam will be reproduced. Gratings can be written to return the diffracted beam on either the same side as the illumination (reflection grating) or the opposite side (transmission grating). The diffraction angle in both configurations is determined by the construction beams. These gratings function as spectral bandpass optical filters because only the range of wavelengths that match the specific written condition are diffracted while all other wavelengths are transmitted with no diffraction. The diffracted signal, which is narrowband in wavelength, is then re-imaged onto a second focal plane. In this way, ambient noise around the desired spectral band can be removed to improve the signal-to-noise ratio of return signals or cleanly separate spectral channels.

A tunable filter uses two elements to achieve wide field of view and very narrow bandpass. The first element is broad, accepting a wide field of view and diffracting a collimated beam. The second element filters the collimated light to a narrow spectral band, and is tunable over a 100 nm range.

An array of volume holograms can be written in a thick material to accept light from a field of view of several degrees. The grating can be designed to diffract filtered light as a collimated beam, or to focus it to the desired detector size. By placing the array near the focus of a collection system, the filter element can be quite small, thus increasing its practical applications.

Volume holograms present an advantageous alternative to traditional beam splitters in multispectral systems. A set of volume holograms, used as a beam splitter for a multispectral camera system, replaces a series of beam splitters and filters for each camera with a single, smaller, lighter-weight, optical element.