Analysis of reflection-type optical switches with intersecting waveguides

The reflection phenomenon of the guided mode in optical switches with intersecting single-mode waveguides is investigated by the wave approach. The guided mode is expanded into an infinite spectrum of plane waves and the condition of total internal reflection is applied. The power reflectivity of the guided mode is calculated and is used to estimate the extinction ratios. It is found that at refractive index variation of about 1 percent, large extinction ratios (>30 dB) are achievable if the refractive index difference between the waveguide core and cladding is smaller than the voltage induced refractive index variation by about one order of magnitude. The intersecting angle is found to be limited to about the critical angle and is required to be large enough to prevent degradation of the extinction ratios and to keep scattering losses small. It is also indicated that by displacing the electrode, to account for the Goos Haenschen shift, it is possible to further reduce the scattering losses