Compact and efficient spectrometers using holographic spectral diversity filters

Abstract

We present a class of spectrometers that work based on diffractive properties of spherical beam volume holograms. The hologram in these spectrometers is recorded by a plane wave and a spherical beam and acts as a spectral diversity filter (SDF), which maps different input wavelengths into different locations in the output plane. The experimental results demonstrate that the spherical beam volume holograms have the capability of separation different wavelength channels of a collimated incident beam. For the analysis of the spherical beam volume hologram, a new theoretical method is introduced and used. It is shown that the experimental results are in good agreement with the theoretical study. Using these results, we demonstrate a Fourier-transform volume holographic spectrometer formed by a Fourier-transform lens, a spherical beam volume hologram, and a CCD. We show that this spectrometer can operate well under spatially incoherent light illumination without using any spatial filter (i.e., slit) in the input. We finally introduce a new implementation of a spectrometer for diffuse source spectroscopy by using only a volume hologram, recorded by two spherical beams, and a CCD. The proposed spectrometer is very compact, inexpensive, less sensitive to optical alignment, and has potentially high throughput that can be widely used in biological and environmental sensing applications.