Electrical and Optical Characterization of BSO Photorefractive Crystals

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Purposes of the present study are to characterize BSO crystals by means of simultaneous optical and electrical measurements, and to clarify the degree of correspondence between material parameters deduced from photorefractive properties and those from electrical properties. Main results obtained are following:1. Optical Characterization: (1) Photorefractive properties such as steady-state intensity of the phase conjugate wave (PCW) and recording time versus light-induced grating spacing characteristics can be fundamentally explained by the "band transport model". (2) Effective acceptor density giving rise to photorefractive properties can be determined from the PCW intensity versus fringe spacing curve. (3) A rigorous method for determining the effect of optical activity on PCW intensity and its polarization angle was developed; a maximum diffraction efficiency can be obtained for the transverse configuration with a static electric field generated along the <001> direction. (4) The pro … More duct of the donor concentration and photoionization cross section was determined from the gain coefficient of the two-beam coupling with running hologram. (5) The dependence of the recording time on the acceptor concentration is quite different between the carrier drift region and the carrier diffusion region.2. Electrical Characterization: (1) Material parameters such as carrier mobility, diffusion length and acceptor concentration, determined from steady-state and dynamic photocurrents, are found to be in reasonably agreement with those from photorefractive measurements. (2) Six impurity levels are detected from thermally stimulated current (TSC) measurements, and their influence on photorefractive properties become evident. (3) A new method to characterize the space charge layer formed underneath electrodes is proposed. (4) The above simple electrical measurements are useful for predicting the photorefractive properties.3. Capability of Optical Information Recordings; The resolving angle and the crosstalk of multiple optical information recordings are studied, and minimum resolving angle without crosstalk is determined. Less