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Existing imaging spectrometers are based either on precision-ruled diffraction gratings or thin holographic gratings. Both rely on angular dispersion of the gratings and require sufficient length (1 m) to achieve high (i.e., subangstrom) resolution. As a result, these devices are bulky, expensive, and inconvenient in field conditions. Volume Bragg gratings, on the other hand, rely on spectral selectivity of thick holograms that produce a single diffraction order and suppress all higher orders. This means that long paths are not necessary to achieve high spectral resolution, which depends on the thickness of the grating instead.