Phase-change metasurface waveguide mode converters and photonic computing systems including a phase-change metasurface waveguide mode converter are described. In an embodiment, the phase-change metasurface waveguide mode converter include a plurality of phase-change antennae comprising a phase-change material and protruding from a surface, wherein each phase-change antenna of the plurality of phase-change antennae is configured to scatter an optical waveguide mode and cause a phase shift of light travelling through an optical waveguide optically coupled thereto. In an embodiment, the phase-change metasurface waveguide mode converter includes the plurality of phase-change antennae configured to alternate between a crystalline phase and an amorphous phase.

Phase-change metasurface waveguide mode converters and photonic computing systems including a phase-change metasurface waveguide mode converter are described. In an embodiment, the phase-change metasurface waveguide mode converter include a plurality of phase-change antennae comprising a phase-change material and protruding from a surface, wherein each phase-change antenna of the plurality of phase-change antennae is configured to scatter an optical waveguide mode and cause a phase shift of light travelling through an optical waveguide optically coupled thereto. In an embodiment, the phase-change metasurface waveguide mode converter includes the plurality of phase-change antennae configured to alternate between a crystalline phase and an amorphous phase.

An optical device includes a rib waveguide that is a thin-film lithium niobate (LN) crystal, a buffer layer that is laminated on the rib waveguide, and an electrode that applies voltage to the rib waveguide. The buffer layer includes a thick-film part that is laminated on a rib of the rib waveguide, and thin-film parts that are laminated on slabs of the rib waveguide, where the slabs are located on both sides of the rib, and that have smaller thicknesses than a thickness of the thick-film part.

An optical device includes a rib waveguide that is a thin-film lithium niobate (LN) crystal, a buffer layer that is laminated on the rib waveguide, and an electrode that applies voltage to the rib waveguide. The buffer layer includes a thick-film part that is laminated on a rib of the rib waveguide, and thin-film parts that are laminated on slabs of the rib waveguide, where the slabs are located on both sides of the rib, and that have smaller thicknesses than a thickness of the thick-film part.

An optical modulator includes a plurality of optical modulation units having a Mach-Zehnder type optical waveguide consisting of two optical waveguides and a high-frequency line pair arranged along the two optical waveguides and consisting of two signal electrodes for applying a pair of differential high-frequency signals, and a plurality of high-resistance conductive films are provided between adjacent high-frequency line pairs separated from the high-frequency line pair.

To effectively prevent the acceleration of the drift phenomenon generated by the application of a high electric field to a substrate through a bias electrode in a waveguide type optical element. A waveguide type optical element includes a substrate (100) having an electro-optic effect, two optical waveguides (104 and 106) disposed on a surface of the substrate, a non-conductive layer (120) which is disposed on the substrate and is made of a material having a lower dielectric constant than the substrate, and a control electrode (150) which is disposed on the non-conductive layer and is intended to generate a refractive index difference between the two optical waveguides by respectively applying electric fields to the two optical waveguides, and the non-conductive layer is constituted of a material which includes silicon oxide, an oxide of indium, and an oxide of titanium and has a ratio between a molar concentration of the titanium oxide and a molar concentration of indium oxide of 1.2 or more, and a voltage generating an electric field of 1 V/μm or more in the substrate is applied to the control electrode.

To effectively prevent the acceleration of the drift phenomenon generated by the application of a high electric field to a substrate through a bias electrode in a waveguide type optical element. A waveguide type optical element includes a substrate (100) having an electro-optic effect, two optical waveguides (104 and 106) disposed on a surface of the substrate, a non-conductive layer (120) which is disposed on the substrate and is made of a material having a lower dielectric constant than the substrate, and a control electrode (150) which is disposed on the non-conductive layer and is intended to generate a refractive index difference between the two optical waveguides by respectively applying electric fields to the two optical waveguides, and the non-conductive layer is constituted of a material which includes silicon oxide, an oxide of indium, and an oxide of titanium and has a ratio between a molar concentration of the titanium oxide and a molar concentration of indium oxide of 1.2 or more, and a voltage generating an electric field of 1 V/μm or more in the substrate is applied to the control electrode.

A multilayer film includes a single-crystal silicon layer, a first layer containing Zr, a second layer containing ZrO.sub.2, and a third layer containing a perovskite oxide having an electrooptic effect. The first layer, the second layer, and the third layer are provided in this order above the single-crystal silicon layer, and the multilayer film is transparent to a wavelength to be used.

A multilayer film includes a single-crystal silicon layer, a first layer containing Zr, a second layer containing ZrO.sub.2, and a third layer containing a perovskite oxide having an electrooptic effect. The first layer, the second layer, and the third layer are provided in this order above the single-crystal silicon layer, and the multilayer film is transparent to a wavelength to be used.

The present disclosure relates to a method including the following steps: a) forming a waveguide from a first material, the waveguide being configured to guide an optical signal; b) forming a layer made of a second material that is electrically conductive and transparent to a wavelength of the optical signal, steps a) and b) being implemented such that the layer made of the second material is in contact with at least one of the faces of the waveguide, or is separated from the at least one of the faces by a distance of less than half, preferably less than a quarter, of the wavelength of the optical signal. The application further relates to a phase modulator, in particular obtained by such a method.