POLARIZATION-INDEPENDENT WAVEGUIDE-TYPE OPTICAL INTERFERENCE CIRCUIT

摘要

A polarization-independent waveguide-type interference circuit provided in accordance with an embodiment of the invention is a Mach-Zehnder interferometer circuit (700) provided with two couplers (722, 724) and two arm waveguides (706, 708) connecting the couplers with each other, each fabricated on a substrate, in which a polarization rotation device (732) is disposed in a groove dividing each of the two arm waveguides into two, the polarization rotation device (732) for converting horizontally polarized light into vertically polarized light and converting vertically polarized light into horizontally polarized light, and birefringence is adjusted by performing laser irradiation or the like partially into at least one of the two arm waveguides such that a difference between birefringence values divided by an optical wavelength to be used is within a range of 2m - 0.2 to 2m + 0.2 (m is an integer including zero), the birefringence values being those integrated linearly along the respective two arm waveguides in an optical signal travelling direction.