Research on Integrated Quantum Photonic Devices

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Research work was performed on novel quantum photonic devices for applications in future quantum information communication systems using photon properties. The obtained results are summarized as follows :1.Quantum theory analysis was performed on nonlinear-optic (NLO) interactions including second-harmonic generation (SHG), sum and difference frequency generations (SFG/DFG), parametric fluorescence (PF) to calculate quantum noises and correlations of the output beams and establish the device design techniques.2.Quantum theory analysis was performed on distributed Bragg reflector (DBR) semiconductor lasers to clarify the conditions for quantum-noise suppression and squeezing characteristics.3.Techniques for fabrication of LiNbO_3 waveguide and quasi-phase matching (QPM) structures were established. New technique using periodic ultraviolet light irradiation and voltage application was developed for formation of QPM structures in MgO:LiNbO_3 crystals.4.Prototype devices using LiNbO_3 waveguides were designed and fabricated. Waveguides were buried by reverse proton-exchange technique for efficiency enhancement. Efficiencies as high as 1400%/W were accomplished in SHG/DFG devices.5.Two types of LiNbO_3 waveguide QPM NLO devices for generation of parallel- and cross- polarized twin photons were designed and fabricated, and the performances close to the theoretical predictions and quantum correlation of the twin photons were experimentally demonstrated.6.DBR lasers for squeezed light generation were designed and fabricated. Quantum efficiencies as high as 70% was obtained, and generation of squeezed light with noise level 0.8dB below the standard quantum limit was demonstrated.7.Generation of quantum-correlated twin beams by two low-noise DBR lasers was experimentally studied, and the possibility was demonstrated.