Polarization-independent all-optical switching in a nonlinearGaInAsP-InP highmesa waveguide with a vertically etched Bragg reflector

摘要

We have theoretically designed and experimentally demonstratednpolarization-independent all-optical switching in a nonlinearnGaInAsP-InP highmesa distributed feedback (DFB) waveguide. The device,nwhich is composed of a highmesa waveguide stripe and a vertically etchednBragg reflector, can be simply fabricated using one-step electron beamnlithography and a reactive ion etching process. The device is suitablenfor integration with other photonic devices such as semiconductornoptical amplifiers and wavelength converters. The structuralnbirefringence of the device has a dependence on the waveguide parametersnsuch as the refractive index and thickness of core and cladding. Thenstructural birefringence was successfully eliminated by adjusting thenwidth of the highmesa waveguide. The nonlinear vertical-groove DFBnhighmesa waveguide is attractive for a polarization-independentnall-optical switch from the viewpoint of a large grating couplingncoefficient, as compared with a grating-loaded DFB highmesa waveguide.nThe polarization dependence of the grating coupling coefficient has alsonbeen investigated experimentally. It is possible to obtain thenpolarization-independent grating coupling coefficient by adjusting thengrating depth in the vertical-groove DFB highmesa waveguide, togethernwith structural zero-birefringence of the device.nPolarization-independent all-optical thresholding and bistable switchingnoperations have been successfully demonstrated in the nonlinearnvertical-groove DFB highmesa waveguide