Experimental characterisation of photorefractive beam coupling in BaTiO<inf>3</inf> crystal at multiple wavelengths

Photorefractive beam coupling in barium titanate crystals is characterised experimentally by measuring the signal beam gain and the exponential gain coefficient at 440 nm, 632.8 nm and 780 nm. The figure of merit parameters such as the change in refractive index, the space charge field and the trap density are estimated using Kukhtarev's theory. A comparative study at multiple wavelengths is presented. The signal beam gain is found to be maximum at 440 nm.