An array of grating couplers is studied to be used for beam steering in a wireless optical communication system. This structure is designed using a rib waveguide with a silicon thickness of 220nm and an etch depth of 70nm using 2μm silica substrate. TE polarized input light with wavelength of 1550nm is coupled into the feed waveguide. The structure is optimized based on the angular coverage, directed power, and beam efficiency of the radiated main beam of an individual grating coupler. The main beam radiated by optimized grating coupler has a beamwidth of 10.3°×30.7°. The designed 1-D array of the fifteen grating couplers provides tunability in the range of around 30 degrees which is required for a point to pint wireless optical communication transmitter.
Simple RC model, which only considered PN junction capacitance and series resistor, and complete circuit model considering parasitic capacitances of a carrier depletion based optical modulators are studied. Modulation efficiency and bandwidth of the modulators are investigated using analytical models and numerical simulations respectively. Through particle swarm optimization (PSO) a repetitive algorithm is applied to find the feasible maximum of circuit bandwidth.
Slow light effect based rib silicon waveguide structures are studied in this paper to enhance modulation efficiency of an
optoelectronic carrier plasma dispersion effect based phase modulator. Center frequency to achieve desired slow down
factor and band width limitations of the structures are investigated through finite element method simulations. Optical
modulation efficiency is modeled and the effects of doping, bias voltage and slow light on its performance are studied.