Planar optical phase shifters with efficient heater placement

Patent metadata

Field	Value
Publication number	US-2018173025-A1
Application number	US-201715846755-A
Country	US
Kind code	A1
Filing date	Dec 19, 2017
Priority date	Dec 21, 2016
Publication date	Jun 21, 2018
Grant date	—

Abstract

Energy efficient thermo-optic phase shifters have a configuration with two sections of a waveguide adjacent for heating by a common heater. A loop section can connect the two heated waveguide sections. Further improved efficiency can be achieved in which the heated sections are curved to allow closer placement of the adjacent waveguides. The heater can be curved to follow the configuration of the curved heated waveguide sections. Energy efficiency gains can be up to approximately a factor of two over corresponding traditional thermo-optical phase shifter designs.

First claim

What is claimed is:

1 . A planar thermo-optic phase shifter comprising a heater and a waveguide on a planar substrate surface establishing the plane of the device, the waveguide comprising two adjacent heated segments having outer edges furthest away from the adjacent heated segment and a loop section connecting the two adjacent heated segments and the heater being positioned over cladding optical material, wherein a projection of the heater into the plane of the waveguides forms a shape that is located between the adjacent heated segments and extends no further than the outer edges of the adjacent heated segments.

2 . The planar thermo-optic phase shifter of claim 1 wherein the waveguide comprises silica glass.

3 . The planar thermo-optic phase shifter of claim 1 wherein the adjacent heated segments are curved over at least a portion of the segments.

4 . The planar thermo-optic phase shifter of claim 1 wherein the adjacent heated segments are curved over the entire sections.

5 . The planar thermo-optic phase shifter of claim 1 wherein the projection of the heater has two separated portions with one portion associated with one waveguide and the other portion being associated with the other waveguide with a gap between the separated heater portions located in the plane of the device between the adjacent heated sections.

6 . The planar thermo-optic phase shifter of claim 1 wherein projection of the heater is confined in the plane of the waveguides to be completely between the area connecting the centers of the adjacent heated sections.

7 . The planar thermo-optic phase shifter of claim 1 wherein the two adjacent heated sections are within a thermal zone surrounding the heater with boundaries of the thermal zone having a temperature increase of 50% of the temperature increase at the hot point relative to ambient temperature, where the hot point is a location on the plane of the waveguides with the highest temperature.

8 . The planar thermo-optic waveguide of claim 1 wherein the loop section has an average radius of curvature selected to result in an optical loss of no more than about 0.5 dB.

9 . The planar thermo-optic phase shifter of claim 1 wherein loop section has an average radius of curvature and wherein the adjacent segments are curved with an average radius of curvature greater than the average radius of curvature of the loop section.

10 . The planar optical phase shifter of claim 9 wherein optical coupling between the adjacent segments is no more than about −27 dB.

11 . The planar optical phase shifter of claim 1 wherein the power consumption of the heater is reduced so that the thermal efficiency has an improvement factor between 1.2 and 2.0 relative to a corresponding phase shifter formed from equivalent materials and heater format with a single waveguide segment within the thermal zone of the heater.

12 . A planar thermo-optic phase shifter comprising a heater and a waveguide on a planar substrate surface establishing the plane of the device, the waveguide comprising two adjacent heated core sections connected by a waveguide core loop such that the optical path is opposite in the adjacent heated core sections, wherein considering a reference plane passing through the center of the waveguides and parallel to the plane of the device, a majority of the heated core sections are curved and a projection of the heater in the reference plane is curved along its length.

13 . The planar thermo-optic phase shifter of claim 12 wherein a projection of the heater in the reference plane is located between the adjacent heated segments and extending no further than the outer edges of the adjacent heated segments.

14 . The planar thermo-optic phase shifter of claim 12 wherein the waveguide comprises silica glass.

15 . The planar thermo-optic phase shifter of claim 12 wherein the loop section has an average radius of curvature, wherein the adjacent heated core section each have an average radius of curvature greater than the average radius of curvature of the loop section, and wherein an open area is formed between the heated core sections and the loop section.

16 . The planar thermo-optic phase shifter of claim 15 wherein a second loop section belonging to a second phase shifter is located within the open area.

17 . The planar thermo-optic phase shifter of claim 15 wherein the adjacent heated core sections are curved along substantially their whole length.

18 . A method for making an energy efficient thermo-optic phase shifter within a planar lightwave circuit, the method comprising:
depositing metal for a resistive heating element onto a planar optical structure comprising an optical waveguide having two adjacent heated sections separated from each other by an average spacing and optically connected to each other by a loop section of the waveguide, wherein a projection of the metal for the restive heating element in the plane of the waveguides is located at least in part between the adjacent heated sections and optionally extending over one or both heated sections with the projection of the metal in the plane of the waveguides extending no further than outer edges of the adjacent heated section of the waveguide wherein the outer edges of the heated sections are evaluated along a width that is perpendicular to a light propagation direction through the heated sections.

19 . The method of claim 18 wherein the metal is deposited using physical vapor deposition and is patterned using photolithography or deposition through a mask.

20 . The method of claim 18 further comprising connecting the heating element to an electrical circuit having a voltage source to provide selective electrical current to the heater to achieve a desired optical phase shift.

21 . The method of claim 18 wherein the two adjacent heated sections are curved over the entire sections.

22 . The method of claim 18 wherein the two adjacent heated sections are within a thermal zone in a reference plane passing through the centers of the waveguides in a plane parallel to the plane of the device with boundaries of the thermal zone having a temperature increase of 50% of the highest temperature increase within the thermal zone relative to ambient temperature.

23 . A thermal optic phase shifter comprising a silica glass waveguide core within silica glass cladding, a heater configured to heat a portion of the silica glass waveguide core, wherein the heat from the heater can provide a phase shift of at least 0.75 degrees per milliwatt heater power.

Assignees

• Neophotonics Corp

Inventors

• Mcgreer Kenneth
• Ho Calvin

Classifications

• G02F2201/06

  integrated waveguide · CPC title

• G02F2202/09

  inorganic glass · CPC title

• G02F2203/48

  Variable attenuator · CPC title

• G02F1/0147 Primary

  based on thermo-optic effects (G02F1/132 takes precedence) · CPC title

• G02F1/2257

  the optical waveguides being made of semiconducting material · CPC title