Abstract: An optical module includes: a modulator containing an InP-based semiconductor material, the modulator including a modulation signal providing unit configured to modulate input light; and an optical integrated circuit optically coupled to the modulator, the optical integrated circuit integrating a plurality of waveguides and a plurality of optical elements including a silicon-based semiconductor material. The optical integrated circuit is configured to output light passed through any one of the waveguides or any one of the optical elements to the modulator, receive modulation light generated by the modulator that modulates the light, and output the modulation light passed through any one of other waveguides or any one of other optical elements.

Abstract: A Mach-Zehnder interferometer circuit (700) is 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 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 2 m-0.2 to 2 m+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.

Abstract: A Mach-Zehnder interferometer circuit (700) is 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 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.