High-order polarization conversion device, optical waveguide device, and DP-QPSK modulator

摘要

A high-order polarization conversion device configured of a planar optical waveguide, includes: a substrate; a lower clad disposed on the substrate; a core including a lower core and an upper core, the lower core being disposed on the lower clad and having a fixed height in a rectangular sectional shape, the upper core being formed of the same material as the lower core and having a fixed height in a rectangular sectional shape that is disposed continuously on the lower core; and an upper clad that is disposed on the core and the lower clad and is formed of the same material as the lower clad. The high-order polarization conversion device performs high-order polarization conversion between TE1 of the start portion and TM0 of the end portion.

主权项

1. A high-order polarization conversion device configured of a planar optical waveguide, comprising:
a substrate; a lower clad disposed on the substrate; a core comprising a lower core and an upper core, the lower core being disposed on the lower clad and having a fixed height in a rectangular sectional shape, the upper core being formed of the same material as the lower core and having a fixed height in a rectangular sectional shape that is disposed continuously on the lower core; and an upper clad that is disposed on the core and the lower clad and is formed of the same material as the lower clad, wherein the core forms an optical waveguide through which light is configured to be guided from a start portion, at which a width of the lower core and a width of the upper core are the same, to an end portion, at which the width of the lower core and the width of the upper core are the same, at the start portion and the end portion, both ends of the upper core in a width direction overlap both ends of the lower core in the width direction, and a section of the core is rectangular shaped, at least one of the width of the upper core and the width of the lower core continuously decreases in a guiding direction of the light between the start portion and the end portion, and neither of the width of the upper core nor the width of the lower core is increased from the start portion to the end portion, at the start portion, an effective refractive index of TE0 is larger than an effective refractive index of TE1, and the effective refractive index of the TE1 is larger than an effective refractive index of TM0, at the end portion of the optical waveguide, the effective refractive index of the TE0 is larger than the effective refractive index of the TM0, and the effective refractive index of the TM0 is larger than the effective refractive index of the TE1, in a portion of the optical waveguide between the start portion and the end portion excluding the start portion and the end portion, the core has a vertically asymmetric structure in which the width of the upper core and the width of the lower core are different, and the high-order polarization conversion device performs high-order polarization conversion between TE1 of the start portion and TM0 of the end portion.