Interband photorefractive effect in β-BBO crystal due to multiphoton excitation by intense ultrashort optical pulses

This paper presents the first experimental observation of interband photo- refractive (PR) effects in β-BBO crystal due to multiphoton excitation with intense ultrashort pulses. In order to fully characterize the PR effects, a sensitive intracavity scheme is developed to magnify the dynamics of nonlinear lenses induced by the PR effects. The reproducible PR phenomena depend strongly on the power, wavelength, and spatial intensity profile of the intense laser pulses and the electro-optic coefficient of the optical materials. Its response time is from tens of seconds to several minutes. The results may be very helpful for us to find a solution to overcome the deleterious influence of multiphoton induced photocharges on nonlinear optical frequency conversions, e.g. optical parametric chirped pulse amplification.