Ultrafast optical thresholding based on two-photon absorption GaAs waveguide photodetectors

We report measurements of the pulsewidth dependence of the two-photon absorption photocurrent in GaAs p-i-n waveguide photodetectors using subpicosecond optical pulses at 1.5 μm. For fixed pulse energy, the photocurrent is observed to depend linearly on the inverse of the optical pulsewidth. A subnanosecond electrical response is also observed. Our results show the feasibility of applying such devices for nonlinear processing in ultrafast optical code-division multiple-access and other ultra high-speed optical network applications.