Holography in frequency-selective materials: swept holograms

A novel technique of recording holograms in spectral hole-burning systems has been developed. During hologram exposure, the frequency of narrow band laser light is `swept' over a frequency range, corresponding to a few homogeneous linewidths of the spectrally selective recording material. Simultaneously the phase of the hologram is controlled as a function of the frequency--the so called phase sweep function. Due to the phase reconstructing properties of holograms, this recording method programs the sample as a spectral amplitude and phase filter. This leads to interesting diffraction phenomena: plane swept holograms show strongly asymmetric signals in conjugated diffraction orders.