Heterodyne pump–probe technique for time-domain studies of optical nonlinearities in waveguides

Abstract

We describe a novel pump–probe technique in which pump and probe pulses are collinear and have parallel polarizations but are still distinguishable. This new technique is especially useful for femtosecond time-domain studies of waveguides. We present experimental results for bulk (V-groove) semiconductor optical amplifiers at 1.5 μm and compare them with results for orthogonally polarized pump–probe measurements. The comparison demonstrates differences that are due to anisotropy of the group velocity as well as of the waveguide nonlinearity.