UBC Theses and Dissertations
Sinusoidal anti-coupling symmetric strip waveguides on a silicon-on-insulator platform Zhang, Fan
Sinusoidal anti-coupling (AC) symmetric waveguides provide a means to design dense waveguide arrays that have minimal inter-waveguide crosstalk for high-density integration of photonic circuits. Also, the polarization sensitivity of sinusoidal AC symmetric waveguides and the reduction of wavelength dependence that is achieved by the sinusoidal waveguides can be used to design broadband polarization beam splitters (PBSs) for polarization diversity systems. In this thesis, I demonstrate the use of sinusoidal bends to suppress the optical power exchange between pairs of symmetric strip waveguides for both transverse-electric (TE) and transverse-magnetic (TM) modes as well as to separate the TE and TM modes into two output symmetric strip waveguides on a silicon-on-insulator platform. I design, model, simulate, and analyze sinusoidal AC symmetric waveguide pairs for both the TE and TM modes. Then, based on the TE sinusoidal AC waveguide structure, I design, simulate, and analyze a PBS using a symmetric directional coupler (DC) with sinusoidal bends. I also compare the modal dispersions of the sinusoidally-bent symmetric DC, which is used in the PBS, with the modal dispersions of an equivalent straight symmetric DC. I measure the fabricated test devices and evaluate their performances. The TE sinusoidal AC device, which has a gap width of 200 nm, has an average crosstalk suppression ratio (SR) of 38.2 dB, and the TM sinusoidal AC device, which has a gap width of 600 nm, has an average crosstalk SR of 34.9 dB over an operational bandwidth of 35 nm. The PBS has a small coupler length of 8.55 μm, has average extinction ratios of 12.0 dB for the TE mode and of 20.1 dB for the TM mode, and has average polarization isolations of 20.6 dB for the through port (the TE mode over the TM mode) and of 11.5 dB for the cross port (the TM mode over the TE mode) over a broad operational bandwidth of 100 nm. All of my devices are easy to fabricate and compatible with complementary metal-oxide-semiconductor technologies.
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