Multiplexed storage of permanent and real-time holograms in photorefractive BSO

Abstract

In this paper we present a technique for storing holograms in crystals of bismuth silicon oxide (BSO) that combines reversible photochromic effects with the more usual real-time photorefractive characteristics. Photochromic effects have been observed before in these sillenite crystals but have generally been considered as a problem rather than as a possible mechanism for holographic storage. As the normal photorefractive (PR) behaviour is unaffected, however, simultaneous spatial multiplexing of both photorefractive (real-time) and photochromic (permanent) holograms is possible in the same crystal volume.

We have demonstrated a number of applications here ranging from image synthesis to holographic interferometry. These operations are mostly based on the inherently separate nature of these two holographic gratings which can lead to relative phase shifts between the two simultaneously scattered fields by shifting the real-time grating with respect to the permanent one, using optical techniques. Furthermore, the permanent holograms also show unexpected dynamic behaviour in which a fast increase in diffraction efficiency is observed upon illumination by a beam at the highly absorbed blue wavelengths. This effect can be used for all-optical switching.

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ORCID for R.W. Eason: orcid.org/0000-0001-9704-2204

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