The use of proton bombardment to reduce photogenerated free carrier effects in passive InGaAsP/InP waveguide devices

Accumulation of photogenerated carriers in passive InGaAsP waveguides at high optical power levels can lead to significant increases in nonlinear loss above those expected from two-photon absorption alone. Two-photon absorption as well as fundamental absorption is a major contributor to the photogeneration of carriers. Additional losses due to the presence of photogenerated carriers has limited conversion efficiency in passive InGaAsP/InP quantum-well frequency converters and is a potential problem in the passive waveguide sections of any monolithically integrated optical circuit that operate with high average powers at wavelengths greater than half the bandgap. Additional losses due to the accumulation of both electrons and holes are on the order of 2-3 cm^-1 per 10¹⁷ cm^-3 of added free-carrier concentrations. We investigate the use of proton bombardment to minimize this free-carrier effect through reductions in carrier lifetime without increasing parasitic losses or degrading the sharpness of the band-edge