A method of manufacturing an optical waveguide element includes: a step of preparing a structure including a substrate and a ridge-shaped optical waveguide layer provided on the substrate and made of a crystal material having an electro-optic effect; a step of depositing all of a cladding layer covering the optical waveguide layer; and a step of performing a heat treatment on the structure on which the cladding layer has been deposited.

A photonics device is described. The photonics devices include at least one electrode and a waveguide. The waveguide includes electro-optic material(s), a ridge, and a slab. A first portion of the waveguide is proximate to the electrode(s), while a second portion of the waveguide includes a bend. The ridge includes a first side and a second side opposite to the first side. Portions of the slab are proximate to the first side and the second side of the ridge in the first portion of the waveguide. A portion of the slab is omitted in the second portion of the waveguide.