Ultracompact polarization converter with a dual subwavelength trench built in a silicon-on-insulator waveguide
ABSTRACT The design and fabrication of an ultracompact silicon-on-insulator polarization converter is reported. The polarization conversion with an extinction ratio of 16 dB is achieved for a conversion length of only 10 μm. Polarization rotation is achieved by inducing a vertical asymmetry by forming in the waveguide core two subwavelength trenches of different depths. By taking advantage of the calibrated reactive ion etch lag, the two depths are implemented using a single mask and etching process. The measured converter loss is −0.7 dB and the 3 dB bandwidth is 26 nm.
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ABSTRACT: We proposed a polarization rotator inspired by stimulated Raman adiabatic passage model from quantum optics, which is composed of a signal waveguide and an ancillary waveguide. The two orthogonal modes in signal waveguide and the oblique mode in ancillary waveguide form a Λ-type three-level system. By controlling the width of signal waveguide and the gap between two waveguides, adiabatic conversion between two orthogonal modes can be realized in the signal waveguide. With such adiabatic passage, polarization conversion is completed within 150 μm length, with the efficiencies over 99% for both conversions between horizontal polarization and vertical polarization. In addition, such a polarization rotator is quite robust against fabrication error, allowing a wide range of tolerances for the rotator geometric parameters. Our work is not only significative to photonic simulations of coherent quantum phenomena with engineered photonic waveguides, but also enlightens the practical applications of these phenomena in optical device designs.Optics Express 07/2013; 21(14):17097-107. · 3.53 Impact Factor
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ABSTRACT: A design of ultra-short integrated polarization rotator (PR) with nonlinear and flat-tip tapers is demonstrated theoretically. Based on mode-evolution theory and three-dimensional (3D) finite-difference time-domain (FDTD) simulation, raised cosine profiled tapers are introduced and optimized in the transition region, which improve the polarized modes coupling and decrease the conversion length to 6 μm for the wavelength of 1.55 μm. Numerical simulations obtain extinction ratio of 32 dB and loss of 0.14 dB with practical material parameters. The method and result presented here can be extremely valuable for applications in polarization diversity circuits.Optics Express 06/2013; 21(12):14888-14894. · 3.53 Impact Factor