Planar optical waveguide element, dual polarization quadrature phase shift keying modulator, coherent receiver, and polarization diversity

Patent metadata

Field	Value
Publication number	US-9500807-B2
Application number	US-201514827397-A
Country	US
Kind code	B2
Filing date	Aug 17, 2015
Priority date	Aug 27, 2014
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

Abstract

A planar optical waveguide element includes: a substrate; and an optical waveguide comprising a core and a cladding, the core being provided on the substrate so as to include first and second core regions arranged in parallel, the cladding having a smaller refractive index than the core. Also, the core forms a preceding-stage mode conversion portion that converts a mode of input light and a subsequent-stage mode conversion portion that converts a mode of light output from the preceding-stage mode conversion portion, and the first and second core regions are spaced apart from each other at an input end of the subsequent-stage mode conversion portion, and a gap between the first and second core regions is continuously decreased along the light waveguide direction such that the first and second core regions are in contact with each other at an output end of the subsequent-stage mode conversion portion.

First claim

What is claimed is:

1. A planar optical waveguide element, comprising:
a substrate; and
an optical waveguide comprising a core and a cladding, the core being provided on the substrate so as to include first and second core regions arranged in parallel, the cladding having a smaller refractive index than the core,
wherein the core forms a preceding-stage mode conversion portion that is configured to convert a mode of input light and a subsequent-stage mode conversion portion that is configured to convert a mode of light output from the preceding-stage mode conversion portion,
sectional shapes of the first and second core regions are not congruent at an input end of the preceding-stage mode conversion portion, and a shape or size of a section of at least one of the first and second core regions is continuously changed along a light waveguide direction such that the sectional shapes of the first and second core regions are congruent at an output end of the preceding-stage mode conversion portion,
the input end of the preceding-stage mode conversion is configured not to perform mode coupling between the first and second core regions, and the output end of the preceding-stage mode conversion portion is configured to perform the mode coupling between the first and second core regions, and
the first and second core regions are spaced apart from each other at an input end of the subsequent-stage mode conversion portion, and a gap between the first and second core regions is continuously decreased along the light waveguide direction such that the first and second core regions are in contact with each other at an output end of the subsequent-stage mode conversion portion.

2. The planar optical waveguide element according to claim 1 ,
wherein, in each of the first and second core regions, a section perpendicular to the light waveguide direction is a rectangular shape.

3. The planar optical waveguide element according to claim 1 ,
wherein, in the preceding-stage mode conversion portion, heights of the first and second core regions are the same, and a width of one of the first and second core regions having a larger section at the input end is continuously decreased along the light waveguide direction such that shapes of sections of the first and second core regions are congruent at the output end.

4. The planar optical waveguide element according to claim 1 ,
wherein, in the subsequent-stage mode conversion portion, a sectional shape of each of the first and second core regions is fixed over an entire length, and
sectional shapes of the first and second core regions at the input end of the subsequent-stage mode conversion portion are the same as the sectional shapes of the first and second core regions at the output end of the preceding-stage mode conversion portion.

5. The planar optical waveguide element according to claim 1 ,
wherein the core includes a slab portion that extends in a width direction of the first and second core regions, and
the slab portion has a smaller height than the first and second core regions, is disposed at least between the first and second core regions, and is formed so as to connect the first and second core regions to each other.

6. The planar optical waveguide element according to claim 5 ,
wherein the slab portion has an outwardly extending region that is formed so as to extend outwardly in the width direction from the first and second core regions.

7. The planar optical waveguide element according to claim 1 ,
wherein the preceding-stage mode conversion portion is configured to convert TE 0 into an odd mode of a super mode of TE 0 , and
the subsequent-stage mode conversion portion is configured to convert the odd mode of the super mode into TE 1 .

8. The planar optical waveguide element according to claim 1 ,
wherein the core includes a curved waveguide that is formed on an input side of the preceding-stage mode conversion portion so as to be curved in plan view of at least one of the first and second core regions, and
in the curved waveguide, the first and second core regions become closer to each other as a distance from the preceding-stage mode conversion portion becomes shorter.

9. The planar optical waveguide element according to claim 1 , further comprising:
an intermediate core region that is provided between the preceding-stage mode conversion portion and the subsequent-stage mode conversion portion so as to connect the preceding-stage mode conversion portion and the subsequent-stage mode conversion portion to each other.

10. The planar optical waveguide element according to claim 1 ,
wherein the core is formed of Si, and the cladding is formed of SiO2.

11. The planar optical waveguide element according to claim 1 , further comprising:
a high-order polarization conversion portion that is connected to an output side of the subsequent-stage mode conversion portion, the high-order polarization conversion portion being configured to convert TE 1 obtained by the subsequent-stage mode conversion portion into TM 0 .

12. A dual polarization quadrature phase shift keying modulator comprising the planar optical waveguide element according to claim 1 .

13. A coherent receiver comprising the planar optical waveguide element according to claim 1 .

14. A polarization diversity comprising the planar optical waveguide element according to claim 1 .

Assignees

• Fujikura Ltd
• Fujikura Ltd

Inventors

• Oka Akira

Classifications

• G02B2006/12038

  Glass (SiO2 based materials) · CPC title

• G02F1/011

  in optical waveguides, not otherwise provided for in this subclass · CPC title

• G02B2006/12061

  Silicon · CPC title

• G02B6/1228 Primary

  Tapered waveguides, e.g. integrated spot-size transformers (for coupling with fibres G02B6/305) · CPC title

• G02F2001/0142

  Physics · mapped topic