Nonlinear phase characteristics of the dispersion interferometer at high-intensity pulses

The dependences of the second harmonic (SH) intensity output by the dispersion interferometer (DI) upon the relative phase of the SH and fundamental waves θ₀ (called phase characteristics) are studied both experimentally and theoretically. It has been found that high irradiance (when self-action effects are not negligible) makes the phase characteristics differ from the cosine type which is usual for linear interferometry. In the case of high power pulsed radiation, a strong dependence of the SH pulse shape on θ₀ was observed. The evolution of the SH pulse shape in the DI output registered as θ₀ varies is checked against the numeric simulation data. By measuring the nonlinear phase characteristics of the DI, the main influence of the slow (response time of ≈ 1 ns) cubic nonlinearity on the frequency doubling of nanosecond pulses is determined for the employed KTP crystals.