科研之友
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摘要
We present a sensitive scheme, for the first time to our knowledge, to observe photo-refraction (PR) effects in some nonlinear optical crystals, e. g. beta-BBO, LBO and BIBO, pumped by an intense ultrashort laser pulse chain. These quite weak effects are "amplified" by sensitive cw intracavity loss modulation. Our results show that they are repeatable and are dependent on pumping power and wavelength, and their response time ranges from tens of seconds to several minutes. The recorded dynamical transitions between the self-focusing to the self-defocusing (or vice versa) induced by the PR effect may be critically important for us to give more insight into the stability of some cascade nonlinear frequency conversions, e. g. multi-stage optical parametric amplifiers.
