EXTERNALLY CONTROLLABLE WAVEGUIDE TYPE HIGHER ORDER MODE GENERATOR

摘要

A higher order mode generator is for converting the 0^th order fundamental guiding mode into higher modes higher than the 0^th order in a waveguide. The waveguide is made from thermo-optic materials in which the refractive index is changed according to the applied electrical power. The waveguide has at least two guiding modes and a straight heater or a linear electrode to invoke refractive index perturbation due to temperature or electric field, respectively while is laid across the waveguide at a certain tilt angle &agr; with respect to the waveguide. When there is no external electric power applied to the heater, the 0^th order single mode light of the waveguide will be propagated through the waveguide without any conversion into higher order modes. When electric current flows through the heater, however, the refractive index of the waveguide beneath the heater either gets lower (polymer) or higher (silica). Therefore, part of the light propagating beneath the heater is reflected at the heater. If the propagation angle of the reflected light is at least larger than the propagation angle of the first order guiding mode of the higher order mode generator, higher order modes will be excited by external control.