Optical device having a stepwise or tapered light input/output part and manufacturing method therefor

A method of manufacturing an optical device comprising an optical waveguide, the optical waveguide comprising a core, a cladding provided around the core, and a light input/output part through which a light beam is input or output, said method comprising:

• preparing a substrate having a principal surface on which a substantially uniform thickness of single-crystalline film is formed, the film having constituent atoms substantially forming a diamond lattice structure and having a surface being neither a (111) plane nor an equivalent plane to the (111) plane;
• subjecting the single-crystalline film to etching showing anisotropy depending on plane orientation while increasing gradually a length of the single-crystalline film which is to be exposed from the etching mask so as to form the film into a terraced shape;
• applying to the terraced shape a photoresist for covering a section where a width is substantially constant and a tapered section where the width changes gradually;
• conducting etching with the photoresist used as an etching mask to pattern the single-crystalline film;
• and
• removing the photoresist, followed by forming a cladding for covering the single-crystalline film,
• the terraced shape being formed by a riser having a face on which the (111) plane or the equivalent plane is exposed.

A method of manufacturing an optical device comprising an optical waveguide, the optical waveguide comprising a core, a first cladding provided around the core, and a light input/output part through which a light beam is input or output, said method comprising:

• a first step of preparing a substrate having a principal surface on which a substantially uniform thickness of single-crystalline film is formed, the film having constituent atoms substantially forming a diamond lattice structure and having a surface being neither a (111) plane nor an equivalent plane to the (111) plane;
• a second step of patterning the single-crystalline film to form a substantially uniform thickness of precursor structure having a precursor of light input/output part;
• a third step of fabricating a structure having a mask formed thereon, the mask exposing the precursor of light input/output part and covering remaining part of the precursor structure;
• a fourth step of subjecting the precursor to etching showing anisotropy depending on plane orientation with the (111) plane and the equivalent plane used as etch-stop planes to thereby form the core in the precursor of the light input/output part;
• a fifth step of removing the mask;
• and
• a sixth step of covering the core with the first cladding to obtain the optical device.

An optical device comprising an optical waveguide provided on a principal surface of a substrate, said optical waveguide comprising:

• a core formed by patterning a single-crystalline film which has constituent atoms substantially forming a diamond lattice structure and has a surface being neither a (111) plane nor an equivalent plane to the (111) plane;
• a first cladding formed by covering the core with a substance having a refractive index smaller than 71.4% of the refractive index of the core;
• and
• a light input/output part through which a light beam is input or output,
• the light input/output part having two or more planes selected from a (111) plane and an equivalent plane to the (111) plane, which expose as etch-stop planes when a precursor of the light input/output part is wet etched using an alkaline solution, and the core having two planes substantially non-parallel to each other among the (111) plane and the equivalent plane.

An optical device comprising an optical waveguide provided on the principal surface of a substrate, said optical waveguide comprising:

• a core;
• a cladding provided around the core,
• the cladding being configured by a substance having a refractive index smaller than 71.4% of the refractive index of the core,
• the core having constituent atoms substantially forming a diamond lattice structure;
• and
• a polarization conversion part which takes part in polarization conversion of light to be propagated,
• the polarization conversion part having a transverse cross section which is taken substantially perpendicularly to a direction of light propagation, and is at least either one of an isosceles triangle with two equal sides configured by (111) planes and an isosceles trapezoid with two equal legs configured by the (111) planes,
• said optical waveguide thereby functioning as a polarization converter.

An optical device comprising an optical waveguide provided on a principal surface of a substrate, said optical waveguide comprising:

• a core formed by patterning a single-crystalline film which has constituent atoms substantially forming a diamond lattice structure and has a surface being neither a (111) plane nor an equivalent plane to the (111) plane;
• a cladding formed by covering the core with a substance having a refractive index smaller than 71.4% of the refractive index of the core;
• and
• a polarization conversion part which takes part in polarization conversion of light to be propagated,
• the polarization conversion part having two or more planes selected from the (111) plane and the equivalent plane, which expose as etch-stop planes when a precursor of the polarization conversion part is wet etched using an alkaline solution,
• the polarization conversion part having a transverse cross section which is taken substantially perpendicularly to a direction of light propagation, and is at least either one of an isosceles triangle with two equal sides configured by the (111) planes and an isosceles trapezoid with two equal legs configured by the (111) planes,
• said optical waveguide thereby functioning as a polarization converter.