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.
© 1992 Optical Society of America
K. L. Hall, G. Lenz, E. P. Ippen, and G. Raybon, "Heterodyne pump-probe technique for time-domain studies of optical nonlinearities in waveguides," Opt. Lett. 17, 874-876 (1992)