Mechanism of photorefractive enhancement of photochromic gratings in BSO - Experimental results and phenomenological modelling

Abstract

We report an increase of more than a factor of 100 in the diffraction efficiency from photochromic gratings written in BSO by uniformly illuminating these gratings with 488 nm light to induce secondary photorefractive gratings. Upon application of an electric field, the phase shift between the two gratings can he varied and under appropriate conditions the diffraction efficiency can increase. The dependence of the enhanced diffraction efficiency as a function of the applied electric field and readout beam polarisation was experimentally investigated for two different crystal orientations. Phenomenological modelling is presented requiring modifications to the phase angle between the photochromic and induced photorefractive gratings in order to reproduce the experimentally observed asymmetry in the increase in the diffraction efficiency. This suggests a periodic modulation of the photorefractive donor/acceptor density, due to the presence of the photochromic grating.

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

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