Holography of space-time events

An investigation is made of the process of holographic recording and a reconstruction of spatial and temporal characteristics of an optical field. It is shown theoretically and experimentally that this can be achieved by recording spectral amplitude–phase holograms in spectrally selective light-sensitive materials capable of storing harmonic components of the reference and object waves. A report is given of experiments on low-temperature solid solutions of large organic molecules in which stable narrow dips in the impurity absorption spectrum can be "burnt out" by photochemical reactions. The causality principle operating via the phase part of a hologram results in selection of one of the images: either a virtual image with a direct time dependence or a real image with a reversed time dependence. An experimental check of the properties of spacetime holograms yielded a fairly high (for practical applications) diffraction efficiency of ~50%.