Shimomura Kazuhiko

We have proposed the optical deflector using arrayed waveguides that have different refractive index by MOVPE selective area growth with asymmetric width of SiO_2 mask pattern on both sides of the arrayed waveguide where the thickness of the each arrayed wavegrade has changed gradually. And the phase change in each arrayed waveguide results the deflection of the light. We have numerically calculated and fabricated the 1×N multi-mode interference (MMI) star coupler using GaInAs/InP MQW structure to input the light equally for each arrayed waveguide. From the numerical calculation, we obtain 0.42dB fluctuation of the output light power in each waveguide in the 1×16 device. In the experiment, 0.88dB fluctuation of the output light was obtained for the 1.56μm wavelength input light. And further, we have numerically calculated the performance of the wavelength divide device by using this arrayed waveguide.

We have researched the optical deflectors, which are capable of random access that the optical switches don't have. In the last, we have proposed the refractive index distribution type optical deflectors by the numerical analysis using FD-BPM. We fabricated the GaInAsP/InP MQW waveguide optical deflectors, and measured the deflection characteristics. The structure of the device using GaInAsP/InP MQW wafer consists of the single mode waveguide where the input light propagates, the grated refractive index region whose refractive index changes by applied voltage. We observed 7μm deflection at the input of 1.46μm wavelength 0.3mW light power where the applied voltage was -2V. This result was equivalent to 1 degree deflection angle.

The purpose of this study is the realization of optical modulator of II-VI MgZnCdSe compounds lattice-matching to InP substrate. In this study, quantum confined stark effect of ZnCdSe/MgZnCdSe multiple quantum well(MQW) grown on InP substrate by molecular beam epitaxy(MBE) was investigated. The reflectance measurement for the MQW structure at room temperature showed the maximum variation of the reflectance at a wavelength near the lowest excitonic transition gap was -6.3% which corresponded to the refractive index venation of -3.4% under 1.87x10^5V/cm electric field apply. This value was larger than that of III-V materials. It is expected that the high performance optical modulator is realized due to the large excitonic effect on II-VI compounds. Fabry-Parot optical modulator which consisted of the spacer layer of the MQW between two multiple layer reflectors were also designed, and the extinction ratio and the insertion loss of the modulator were estimated. Furthermore MgZnCdSe multiple layer reflectors were grown an maximum reflectance of 98.0% was obtained at 596nm

We have fabricated the optically controlled MOSFET by using direct wafer bonding technique. It was the long wavelength light detector integrated on Si substrate, and we have measured its optical response characteristics. The device modulated the drain-to-source current using the potential change of the light absorption region when the laser light was irradiated. The response speed depends on the light absorption region and the MOSFET and it is possible to use under tens GHz frequency As a resnilt of the measurement, the maximum modulation current ΔI_<DS> of 560μA, the maximum Photo screening voltage ΔV_<PS> of 0.4V, and the maximum responsivity R of 288A/W were obtained, when the input light wavelength was λ=1.50μm.