Abstract

The cascading phenomena produced during Second Harmonic Generation (SHG) in a nonlinear crystal is responsible for a nonlinear phaseshift sensed by the laser beam during its propagation in the crystal. The sign and amplitude of the induced n₂(Δk) can be controlled by the phase mismatch Δk = k(2ω)-k((ω) between the fundamental -k(ω)- and the harmonic -k(2ω)- wave vectors propagating in the crystal.¹ Therefore, this phenomenon makes its possible to compensate for spatial and temporal nonlinear phase shift occurring in the optical elements used in amplification chains. However, for such a compensation one needs to measure accurately both spectral and spatial amplitude of the cascading phenomena versus Ak. In femtosecond range, the Kerr lens induced by cascading phenomena has been measured by z-scan technique.² Hereafter, we demonstrate that spectral interferometry is a well suited technique for measuring the spectral phase shift Δϕ (ω) due to cascading phenomena produced by femtosecond pulses during SHG.

© 2002 Optical Society of America