Photorefractive effect in a BaTiO_3 crystal at the 15-μm wavelength regime by two-photon absorption

We demonstrate the extension of the photorefractive effect in BaTiO(3) crystals to the 1.5-microm wavelength regime, which is obtained by two-photon absorption induced by intense femtosecond light pulses. The strong dependence of the effect on the light's intensity permits nondestructive readout of the photorefractively induced pattern by low-intensity light. One can thus use the photorefractive effect in the 1.5-microm regime to form optical components for communication applications.