Tunable Optical Element

Patent metadata

Field	Value
Publication number	US-2016356959-A1
Application number	US-201615013534-A
Country	US
Kind code	A1
Filing date	Feb 2, 2016
Priority date	Jun 5, 2015
Publication date	Dec 8, 2016
Grant date	—

Abstract

The disclosure demonstrates n-doped resistive heaters in silicon waveguides showing photoconductive effects with high responsivities on the order of 100 mA/W. These photoconductive heaters, integrated into microring resonator (MRR)-based filters, can be used to automatically tune and stabilize the filters' resonance wavelength to the input laser-wavelength. This is achieved without requiring dedicated defect implantations, additional material depositions, dedicated photodetectors, or optical power tap-outs. Series-coupled higher-order MRR-based filters can be automatically tuned by sequentially aligning the resonance of each MRR to the laser-wavelength by using photoconductive heaters to monitor the light intensity in each MRR. Embodiments allow for the automatic wavelength stabilization of MRR-based optical circuits.

First claim

1 . A tunable optical element comprising:
a semiconductor material arranged to form a microring resonator (MRR); and an in-resonator photoconductive heater (IRPH) comprising at least a portion of the semiconductor material doped at a first doping level such that the IRPH both heats the MRR in response to an electrical input applied to the IRPH and is electrically responsive to light within the MRR, producing a photocurrent responsive to the light in the MRR.

2 . The tunable optical element as claimed in claim 1 further comprising electrical contacts for providing the electrical input to the IRPH to control the degree of heating, and for supplying the photocurrent to a feedback circuit such that the photocurrent produced by the IRPH can be used by the feedback circuit to control the degree of heating.

3 . The tunable optical element as claimed in claim 2 wherein the semiconductor material further includes inner and outer portions doped at a second doping level, the inner and outer portions configured to provide low-resistance electrical contacts to the IRPH.

4 . The tunable optical element as claimed in claim 3 wherein:
the semiconductor material is silicon shaped as a waveguide;
the IRPH comprises an n-doped middle portion of the semiconductor material; and
wherein the second doping level comprises n++ doping.

5 . The tunable optical element as claimed in claim 1 wherein the photocurrent produced by the IRPH is dependent on intensity of the light in the MRR.

6 . The tunable optical element as claimed in claim 5 wherein the electrical input supplied via the electrical contacts heats the IRPH to adjust such that the MRR resonates at a desired wavelength.

7 . The tunable optical element as claimed in claim 6 wherein the MRR comprises a circular ring, and wherein the tunable optical element further comprises an input waveguide for supplying light at a plurality of wavelengths into the MRR, and a drop waveguide for outputting the desired wavelength, which resonates within the MRR.

8 . The tunable optical element as claimed in claim 6 wherein the electrical responsiveness to light is due to absorption of light by defects within the semiconductor material induced by doping.

9 . The tunable optical element as claimed in claim 6 further comprising a plurality of MRRs, together with corresponding IRPHs, communicatively coupled together.

10 . The tunable optical element as claimed in claim 3 wherein the second doping level is higher than the first doping level.

11 . The tunable optical element as claimed in claim 2 wherein the electrical contacts comprise same contacts for providing the electrical input to the IRPH; and for supplying the photocurrent to the feedback circuit such that the photocurrent produced by the IRPH can be used by the feedback circuit to control the degree of heating.

12 . A tunable optical element comprising:
a microring resonator (MRR) formed from a semiconductor material; an integrated in-resonator photoconductive heater (IRPH) formed by doping the semiconductor material and integrated with said MRR, said IRPH acting as both a resistive heater and a photoconductive material; electrical contacts; and a feedback circuit connected through the electrical contacts to a more heavily doped region of the semiconductor material to both control the heating of the IRPH and to measure a photoconductive response of said IRPH in order to tune said MRR.

13 . The tunable optical element as claimed in claim 12 wherein the semiconductor material is silicon shaped as a ring waveguide and comprising an n doped ring region to form the IRPH, and a n++ doped contact region to reduce the electrical resistance of the n++ doped contact region to facilitate flow of electrical current between the ring region and the electrical contacts.

14 . The tunable optical element as claimed in claim 13 wherein the electrical contacts comprise dual-purpose contacts to provide the electrical input to the IRPH to control a degree of heating, and to supply photocurrent produced in the ring region to the feedback circuit such that the photocurrent can be used by the feedback circuit to control the degree of heating of the ring region.

15 . The tunable optical element tunable optical element as claimed in claim 14 wherein the photocurrent produced in the ring region is dependent on a degree to which the ring waveguide resonates with a wavelength of light in the ring waveguide.

16 . The tunable optical element as claimed in claim 14 wherein the feedback circuit tunes the ring waveguide by adjusting the electrical current supplied, such that ring waveguide continues to resonate at a desired wavelength.

17 . The tunable optical element as claimed in claim 16 wherein the ring waveguide is circular in shape.

18 . The tunable optical element as claimed in claim 16 further comprising a plurality of such MRRs and associated IRPHs communicatively coupled together.

19 . The tunable optical element as claimed in claim 18 wherein the feedback circuit tunes each of the plurality of MRRs in sequence in order to center the filter response at the desired wavelength.

20 . A method for using a doped semiconductor waveguide arranged in a loop such that light can circulate around the loop, the method comprising:
using a pair of electrical contacts to connect the doped semiconductor waveguide to a feedback circuit; applying an electrical input via the pair of contacts to heat the doped semiconductor waveguide; and using the same pair of electrical contacts to measure a photoconductive response of the doped semiconductor waveguide to control the degree of heating.

Assignees

• Jayatilleka Hasitha
• Murray Kyle Jacob
• Chrostowski Lukas
• Shekhar Sudip
• Huawei Tech Canada Co Ltd

Inventors

• Jayatilleka Hasitha
• Murray Kyle Jacob
• Chrostowski Lukas
• Shekhar Sudip

Classifications

• G02B6/29395 Primary

  configurable, e.g. tunable or reconfigurable (switching G02B6/35) · CPC title

• G02B6/2934

  Fibre ring resonators, e.g. fibre coils · CPC title

• G02B6/29382

  including at least adding or dropping a signal, i.e. passing the majority of signals · CPC title

• G02F1/3132

  of directional coupler type · CPC title

• G02F1/0147

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