1.5μM Polarization Entanglement Generation Based On Silicon Wire Waveguides

Quantum light sources in1.5m band are important devices in quantumteleportation and quantum information processing. Due to its small size,strong ability of light control, high third-order optical nonlinear coefficient,and extremely narrow Raman scattering peak, the silicon wire waveguide isone of the most promising materials to realize the on-chip integrated quantumlight sources. Under the support of the National Basic Research Program (973Program) project of China (“Quantum light source for quantum network(2011CBA00303)”), the polarization entanglement generation based on thebirefringence in silicon wire waveguides is investigated theoretically andexperimentally in this dissertation.A new scheme of polarization entanglement generation in opticalcommunication band, which is based on the birefringence in silicon wirewaveguides, is proposed and demonstrated experimentally. The birefringenceis utilized to suppress the vector spontaneous four-wave mixing process, andthe pump light polarization is adjusted to achieve the maximum polarizationentangled state. The two-photon interference under two non-orthogonalpolarization bases and polarization indistinguishability at single sides aremeasured to demonstrate polarization entanglement generation. The visibilityof the measured two-photon interference fringes is86%, with the accidentalcoincidence counts subtracted. No polarization maintaining loops or anysilicon polarization rotators are need in this scheme. It provides a simple wayto realize silicon integrated sources for polarization entanglement generation.A method to measure the output end coupling efficiency between siliconwire waveguides and optical fibers is proposed and demonstrated based on thecorrelated photon pair generation in silicon wire waveguides. The output endcoupling efficiency can be calculated by measuring the single side counts,coincidence and accidental coincidence counts. The correlated photon pairgeneration in silicon wire waveguides is demonstrated experimentally, with the CAR>9at room temperature. The output end coupling efficiency betweenSWW sample and optical fibers is5.38dB±0.08dB measured with this method.It provides a way to investigate and optimize the coupling processes at thewaveguide input and output end separately. This method can be expanded tothe waveguides made of other third-order nonlinear materials.A new mode-size convertor composed of a thin silicon nitride waveguideis proposed. The theoretical analysis shows high coupling efficiency betweenthe mode-size convertor and lensed fibers. The experiment preparationscheme is proposed and some critical process steps are explored. Comparedwith those schemes that have been reported, it is more efficient, simpler andeasier for preparation, which provides an easier way to solve the couplingproblem between silicon waveguides and optical fibers.