We have improved fabrication processes of periodically inverted AlGaAs waveguides for highly efficient quasi-phase-matched wavelength conversion. In order to reduce propagation losses in waveguiding devices fabricated based on sublattice reversal epitaxy, we have introduced template planarization by chemical mechanical polishing and low-temperature regrowth technique. Corrugations at the core/ clad interface and the propagation loss at 1.55 mm has been reduced to 40 nm and 9 dB/cm, respectively. First-order quasi-phase-matched second-harmonic generation was demonstrated at 1.55 mm fundamental wavelength with a 1.47-mm-long device. Obtained internal conversion efficiency is 2.2%/W which is one order of magnitude lower than the theoretical value for an ideal lossless waveguide. A significant increase in the conversion efficiency is expected with a redesign of the device and further optimization of the fabrication processes. #

We have fabricated periodically-inverted GaP/AlGaP waveguiding devices and succeeded in achieving quasi phase matching in an optical parametric interaction for the first time. Quasi-phase-matched parametric fluorescence signals at 1.6 and 3.1 m were generated from 1.064 m pump, and the estimated efficiency agreed with the theoretical one. The temperature tuning rates of type-I quasi-phase-matched interaction are À0:5 nm/K for signal in 1.6 m range and 2.0 nm/K for idler in 3.1 m range, respectively.

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Recent progress of semiconductor-based quasi-phase-matching (QPM) wavelength conversion devices is reviewed. Compound semiconductors are promising materials for generating coherent light in the mid-infrared (IR) region because of their transparencies in the long-wave IR range and high second-order nonlinearities. Bulk-type and waveguide-type QPM devices have been developed using GaAs, and their high potentials are now being demonstrated. Wider-bandgap semiconductors are also studied as materials for the next-generation wavelength conversion devices.