High-order polarization conversion device, optical waveguide device, and DP-QPSK modulator

Patent metadata

Field	Value
Publication number	US-9557482-B2
Application number	US-201514976603-A
Country	US
Kind code	B2
Filing date	Dec 21, 2015
Priority date	Jun 27, 2013
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

A high-order polarization conversion device configured of a planar optical waveguide, includes: a substrate; a lower clad disposed on the substrate; a core including a lower core and an upper core, the lower core being disposed on the lower clad and having a fixed height in a rectangular sectional shape, the upper core being formed of the same material as the lower core and having a fixed height in a rectangular sectional shape that is disposed continuously on the lower core; and an upper clad that is disposed on the core and the lower clad and is formed of the same material as the lower clad. The high-order polarization conversion device performs high-order polarization conversion between TE 1 of the start portion and TM 0 of the end portion.

First claim

What is claimed is:

1. A high-order polarization conversion device configured of a planar optical waveguide, comprising:
a substrate;
a lower clad disposed on the substrate;
a core comprising a lower core and an upper core, the lower core being disposed on the lower clad and having a fixed height in a rectangular sectional shape, the upper core being formed of the same material as the lower core and having a fixed height in a rectangular sectional shape that is disposed continuously on the lower core; and
an upper clad that is disposed on the core and the lower clad and is formed of the same material as the lower clad, wherein
the core forms an optical waveguide through which light is configured to be guided from a start portion, at which a width of the lower core and a width of the upper core are the same, to an end portion, at which the width of the lower core and the width of the upper core are the same,
at the start portion and the end portion, both ends of the upper core in a width direction overlap both ends of the lower core in the width direction, and a section of the core is rectangular shaped,
at least one of the width of the upper core and the width of the lower core continuously decreases in a guiding direction of the light between the start portion and the end portion, and neither of the width of the upper core nor the width of the lower core is increased from the start portion to the end portion,
at the start portion, an effective refractive index of TE 0 is larger than an effective refractive index of TE 1 , and the effective refractive index of the TE 1 is larger than an effective refractive index of TM 0 ,
at the end portion of the optical waveguide, the effective refractive index of the TE 0 is larger than the effective refractive index of the TM 0 , and the effective refractive index of the TM 0 is larger than the effective refractive index of the TE 1 ,
in a portion of the optical waveguide between the start portion and the end portion excluding the start portion and the end portion, the core has a vertically asymmetric structure in which the width of the upper core and the width of the lower core are different, and
the high-order polarization conversion device performs high-order polarization conversion between TE 1 of the start portion and TM 0 of the end portion.

2. The high-order polarization conversion device according to claim 1 , wherein
in the optical waveguide between the start portion and the end portion excluding the start portion and the end portion, the width of the lower core is consistently larger than the width of the upper core, and a lower side of the upper core is consistently included in an upper side of the lower core in a section perpendicular to a direction in which the light is guided.

3. The high-order polarization conversion device according to claim 2 , wherein
in the optical waveguide between the start portion and the end portion excluding the start portion and the end portion, both ends of the upper core in a width direction are consistently arranged without overlapping both ends of the lower core in the width direction.

4. The high-order polarization conversion device according to claim 2 , wherein
between the start portion and the end portion, one end of the upper core in a width direction consistently overlaps one end of the lower core in the width direction.

5. The high-order polarization conversion device according to claim 1 , wherein
at the start portion, a height of the core is 210 nm to 230 nm, and a width of the core is 700 nm or more, and
at the end portion, the height of the core is 210 nm to 230 nm, and the width of the core is 620 nm or less.

6. The high-order polarization conversion device according to claim 1 , wherein
the lower core and the upper core are formed of Si, and the lower clad and the upper clad are formed of SiO 2 .

7. The high-order polarization conversion device according to claim 1 , wherein
the width of the upper core decreases from the start portion to an intermediate portion and is fixed from the intermediate portion to the end portion, and the width of the lower core is fixed from the start portion to the intermediate portion and decreases from the intermediate portion to the end portion.

8. An optical waveguide device, comprising:
the high-order polarization conversion device according to claim 1 ; and
a directional coupler configured to include a first optical waveguide, to which the high-order polarization conversion device is not connected, and a second optical waveguide connected to the start portion of the high-order polarization conversion device, wherein
TE 0 is guided through the first optical waveguide, TE 1 is guided through the second optical waveguide, and TE 0 of the first optical waveguide is configured to be coupled to TE 1 of the second optical waveguide.

9. The optical waveguide device according to claim 8 , wherein
a difference between an effective refractive index of TE 0 of the first optical waveguide and an effective refractive index of TE 0 of the second optical waveguide is 0.2 or more.

10. A DP-QPSK modulator comprising the optical waveguide device according to claim 8 .

Assignees

• Fujikura Ltd

Inventors

• Oka Akira
• Goi Kazuhiro
• Ogawa Kensuke
• Kusaka Hiroyuki

Classifications

• G02B6/126 Primary

  using polarisation effects {(G02B6/1226 takes precedence)} · CPC title

• G02B2006/12038

  Glass (SiO2 based materials) · CPC title

• G02B6/2726

  in or on light guides, e.g. polarisation means assembled in a light guide · CPC title

• G02B6/105

  having optical polarisation effects · CPC title

• G02B6/1228

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