GUIDED-WAVE MEASUREMENTS OF REAL-EXCITATION OPTICAL NONLINEARITIES INA TENSILE-STRAINED INGAAS ON INP QUANTUM-WELL AT 1.5 MU-M

Reported are measurements, in the 1.5 mum wavelength region, of the no nlinear refractive and absorptive changes, associated with real excita tion processes, in a tensile-strained 6.7 nm thick In0.47Ga0.53As/InP single quantum well centred within a linear InGaAs/InP multiple quantu m well waveguide Fabry-Perot (PF) cavity. The refractive index changes were determined using two different pump/probe techniques: direct mea surement of the refractive index changes in a FP cavity, and also via a Kramers-Kronig transformation of the absorption changes in the wavel ength region of the bandgap resonance. Comparing these two measurement s, reveals that there is a significant non-resonant contribution to th e total refractive index changes in the SQW material, which is attribu ted to an enhanced free carrier absorption contribution due to carrier confinement in the two-dimensional quantum well. At wavelengths near the bandedge, index and absorption changes of DELTAn=-0.12 and DELTAal pha=8300 cm-1, respectively, were observed, while DELTAn=-0.07 was mea sured at a wavelength over 90 nm from the bandedge. These index change s are sufficient to allow the design of, polarisation independent, opt ical switches based on carrier induced refractive index changes such a s bistable Fabry-Perots, with predicted sub-mW switch powers.