OPTICAL DEVICE HAVING A STEPWISE OR TAPERED LIGHT INPUT/OUTPUT PART AND MANUFACTURING METHOD THEREFOR

• US 20160223748A1
• Filed: 04/08/2016
• Published: 08/04/2016
• Est. Priority Date: 09/20/2013
• Status: Active Grant

• Current Assignee: National Institute of Advanced Industrial Science and Technology (Government of Japan), OKI Electric Industry Company Limited
• Original Assignee: National Institute of Advanced Industrial Science and Technology (Government of Japan), OKI Electric Industry Company Limited, Photonics Electronics Technology Research Association
• Inventors: ONO, Hideki, HORIKAWA, Tsuyoshi, HIRAYAMA, Naoki
• Granted Patent: US 9,869,815 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/12147 Coupler
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/126 using polarisation effects G02B6/1226 takes precedence
• CPC Class Codes: G02B 6/136 by etching
• CPC Class Codes: G02B 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence

Abstract

An optical device includes an optical waveguide provided on a principal surface of a substrate. The optical waveguide includes a core and a cladding provided around the core. The cladding is configured by a substance having a refractive index smaller than 71.4% of the refractive index of the core. The core has constituent atoms substantially forming a diamond lattice structure. The optical waveguide has a light input/output part through which a light beam is input and/or output. The light input/output part decreases stepwise in thickness towards an output end while tapering down in its width. The core is provided in the light input/output part to have a (111) plane or an equivalent plane to the (111) plane exposed on a face of a riser of the stepwise thickness of the light input/output part.

Claims

1. An optical device comprising an optical waveguide provided on a principal surface of a substrate, said optical waveguide comprising a core and 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,

said optical waveguide comprising a light input/output part through which a light beam is input and/or output,

the light input/output part decreasing stepwise in thickness towards an output end while tapering down in its width,

the core being provided in the light input/output part to have a (111) plane or an equivalent plane to the (111) plane exposed on a face of a riser of the stepwise thickness of the light input/output part.

2. The optical device according to claim 1, wherein the core comprises Si as a constituent element.

3. An optical device comprising an optical waveguide provided on a principal surface of a substrate, said optical waveguide comprising a core and 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,

said optical waveguide further comprising a light input/output part through which a light beam is input and/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, and the core having two planes substantially non-parallel to each other among the (111) plane and the equivalent plane.

4. The optical device according to claim 3, wherein the light input/output part is connected to a body of the core and has an end portion,

the body of the core having a top face opposed to the principal surface and being a (100) plane or an equivalent plane of the (100) plane,

the light input/output part comprising a connective part and a functional part,

the functional part having a transverse cross section which is taken substantially perpendicularly to a direction of light propagation and connected to the body of the core while placing the connective part in between being 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, and being tapered towards the end portion so that the transverse cross section monotonously shrinks while keeping similarity,

the connective part being surrounded by connective planes configured by a (110) plane and an equivalent plane to the (110) plane,

the functional part thereby functioning as a spot-size converter.

5. The optical device according to claim 3, wherein the light input/output part is connected to a body of the core and has an end portion,

the body of the core having a top face opposed to the principal surface being a (110) plane or an equivalent plane to the (110) plane,

the light input/output part having a connective part and a functional part,

the functional part having a transverse cross section which is taken substantially perpendicularly to a direction of light propagation and connected to the body of the core while placing the connective part in between being 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, and being tapered towards the end portion so that the transverse cross section monotonously shrinks while keeping similarity,

the connective part being surrounded by connective planes configured by the (111) plane and the equivalent plane to the (111) plane,

the functional part thereby functioning as a spot-size converter.

6. The optical device according to claim 3, wherein the light input/output part is connected to a body of the core and has an end portion,

the body of the core having a top face opposed to the principal surface being a (112) plane or an equivalent plane to the (112) plane,

the light input/output part having a connective part and a functional part, each of which has a generally rectangular transverse cross section taken substantially perpendicularly to the direction of light propagation, and is monotonously tapered in width towards the end portion, the width being defined a length measured in a direction that is substantially parallel with the principal surface of the substrate and perpendicular to the direction of light propagation,

the connective part being surrounded by connective planes configured by the (111) plane connected to the top face, and an equivalent plane that is equivalent to the (111) plane and connected to a side face of the body of the core, and has a generally rectangular transverse cross section taken substantially perpendicularly to the direction of light propagation,

the functional part having a flat part configured by a (112) plane, the end portion being connected to the flat part and being configured by the (111) plane,

the functional part thereby functioning as a spot-size converter.

7. The optical device according to claim 3, wherein the light input/output part has a plurality of cores arranged so as to cross a direction of light propagation, and substantially in parallel to each other with a predetermined period,

each of the cores which has a transverse cross section taken in a direction crossing substantially perpendicularly to all of the plurality of cores and to the principal surface being 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,

the light input/output part thereby functioning as a grating coupler.

8. 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.

9. The optical device according to claim 8, wherein the connective part has a plurality of sub-connective parts arrayed in series in a direction of light propagation,

each of the sub-connective parts having a sub-connective plane as a slope, and a sub-plane connected to the sub-connective plane and having a same plane orientation as a top face of the core,

the sub-connective planes having the same plane orientation for all of the plurality of sub-connective parts, and being configured to shrink stepwise in area in the direction of light propagation.

10. The optical device according to claim 8, wherein the light input/output part has an end portion truncated substantially perpendicularly to a direction of light propagation, ensuring a size of cross section capable of allowing both of TE wave and TM wave to propagate therethrough.

11. The optical device according to claim 8, wherein the light input/output part has provided therearound with a second cladding having a refractive index substantially larger than that of the first cladding and substantially smaller than that of the core,

the first cladding extending around the second cladding.

12. 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.

13. 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.