# US 10,481,333 B2 · Athermal silicon photonics wavelength locker and meter

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 10,481,333 B2
- Document ID: US10481333B2
- Status: Granted
- Kind: B2
- Application number: 15/642,589
- Filed: 2017-07-06
- Published: 2019-01-10
- Granted: 2019-11-19
- Earliest claimed: 2017-07-06
- Assignees: MACOM Technology Solutions Holdings, Inc.
- Applicants: MACOM Technology Solutions Holdings, Inc.
- Inventors: Haruhisa Soda
- Web page: https://patentgrep.com/patent/US10481333B2

## CPC

- G02B 6/29344: {operating by modal interference or beating, i.e. of transverse modes, e.g. zero-gap directional coupler, MMI}
- G02B 6/12007: {forming wavelength selective elements, e.g. multiplexer, demultiplexer}
- G02B 6/29352: {in a light guide}
- H01S 5/12: the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers (comprising a photonic bandgap structure H01S5/11; surface-emitting lasers H01S5/18)
- H04B 10/5161: {Combination of different modulation schemes}
- H04B 10/572: Wavelength control
- H04J 14/02: Wavelength-division multiplex systems
- G02B 2006/12097: {Ridge, rib or the like}
- H01S 5/0687: Stabilising the frequency of the laser
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H04B: TRANSMISSION
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

A wavelength locker includes first and second waveguides to guide light. The wavelength locker also includes a multimode interference (MMI) coupler having a number of inputs and outputs. First and second inputs of the MMI coupler are coupled to outputs of the first and second waveguides. The MMI coupler merges light from the first and second waveguides to generate an interference pattern of light. The MMI coupler then outputs a plurality of phase shifted versions of the interference pattern. The wavelength locker also includes an interference pattern selector configured to receive signals corresponding, respectively, to light output from the outputs of the MMI coupler. The interference pattern selector is also configured to select one or more outputs of the MMI coupler based on power levels of the interference patterns output from the MMI coupler and a predetermined frequency of a telecommunications frequency grid.

## Claims

### Claim 1

A wavelength locker, comprising:
a first multimode interference (MMI) coupler, at least one input of the first MMI coupler being coupled to a coherent source of light;
a first waveguide having an input coupled to a first output of the first MMI coupler;
a second waveguide having an input coupled to a second output of the first MMI coupler;
a second MMI coupler having a plurality of inputs and a plurality of outputs, a first of the plurality of inputs of the second MMI coupler being coupled to an output of the first waveguide, and a second of the plurality of inputs of the second MMI coupler being coupled to an output of the second waveguide; and
an interference pattern selector configured to:
receive a plurality of signals corresponding, respectively, to light output from the plurality of outputs of the second MMI coupler, the plurality of outputs of the second MMI coupler comprising at least three outputs; and
select a pair of the plurality of outputs of the second MMI coupler based on power levels of individual ones of the plurality of outputs and a predetermined frequency of a telecommunications frequency grid.

### Claim 2 (depends on 1)

The wavelength locker according to claim 1, wherein the interference pattern selector is configured to select the pair of the plurality of outputs based on the predetermined frequency of the telecommunications frequency grid and a predetermined phase shift.

### Claim 3 (depends on 2)

The wavelength locker according to claim 2, wherein the predetermined phase shift is about 180 degrees.

### Claim 4 (depends on 1)

The wavelength locker according to claim 1, wherein the first waveguide comprises a rib waveguide having a first length and the second waveguide comprises a wire waveguide having a second length.

### Claim 5 (depends on 4)

The wavelength locker according to claim 4, wherein the first length is greater than the second length.

### Claim 6 (depends on 1)

The wavelength locker according to claim 1, wherein the first waveguide, the second waveguide, and the second MMI coupler operate as an interferometer at a free spectral range based on the telecommunications frequency grid.

### Claim 7 (depends on 1)

The wavelength locker according to claim 1, further comprising a plurality of photodetectors configured to convert the light output from the plurality of outputs of the second MMI coupler to the plurality of signals for the interference pattern selector.

### Claim 8 (depends on 1)

The wavelength locker according to claim 1, further comprising:
a third waveguide having an input coupled to a third output of the first MMI coupler;
a fourth waveguide having an input coupled to a fourth output of the first MMI coupler; and
a third MMI coupler having a plurality of inputs and a plurality of outputs, a first of the plurality of inputs of the third MMI coupler being coupled to an output of the third waveguide, and a second of the plurality of inputs of the third MMI coupler being coupled to an output of the fourth waveguide.

### Claim 9 (depends on 8)

The wavelength locker according to claim 8, wherein the interference pattern selector is further configured to:
receive a plurality of signals corresponding, respectively, to light output from a plurality of outputs of the third MMI coupler; and
select a pair of the plurality of outputs of the third MMI coupler based on another predetermined frequency of a telecommunications frequency grid.

### Claim 10

A method of wavelength locking, comprising:
guiding light along a first waveguide;
guiding light along a second waveguide, at least one of the first waveguide or the second waveguide introducing a propagation delay;
merging the light from the first waveguide with the light from the second waveguide in a multimode interference (MMI) coupler to generate an interference pattern of light;
outputting, from a plurality of outputs of the MMI coupler, a plurality of phase shifted versions of the interference pattern, the plurality of outputs of the MMI coupler comprising at least three outputs;
converting the plurality of phase shifted versions of the interference pattern into a plurality of signals; and
selecting, by a processing circuit, a pair of the plurality of outputs of the MMI coupler based on power levels of individual ones of the plurality of outputs of the MMI coupler and a predetermined frequency of a telecommunications frequency grid.

### Claim 11 (depends on 10)

The method of wavelength locking according to claim 10, wherein the first waveguide comprises a rib waveguide having a first length and the second waveguide comprises a wire waveguide having a second length.

### Claim 12 (depends on 11)

The method of wavelength locking according to claim 11, wherein the first waveguide, the second waveguide, and the MMI coupler operate as an interferometer at a free spectral range based on the telecommunications frequency grid.

### Claim 13

A wavelength locker, comprising:
a first waveguide to guide light;
a second waveguide to guide light, at least one of the first waveguide or the second waveguide introducing a propagation delay;
a multimode interference (MMI) coupler having a plurality of inputs and a plurality of outputs, a first of the plurality of inputs being coupled to an output of the first waveguide, and a second of the plurality of inputs being coupled to an output of the second waveguide, the plurality of outputs of the MMI coupler comprising at least three outputs; and
an interference pattern selector configured to:
receive a plurality of signals corresponding, respectively, to light output from a plurality of outputs of the MMI coupler; and
select a pair of the plurality of outputs of the MMI coupler based on power levels of individual ones of the plurality of outputs and a predetermined frequency of a telecommunications frequency grid.

### Claim 14 (depends on 13)

The wavelength locker according to claim 13, wherein the first waveguide comprises a rib waveguide having a first length, the second waveguide comprises a wire waveguide having a second length, and the first length is greater than the second length.

### Claim 15 (depends on 13)

The wavelength locker according to claim 13, wherein the first waveguide, the second waveguide, and the MMI coupler operate as an interferometer at a free spectral range based on the telecommunications frequency grid.

### Claim 16 (depends on 13)

The wavelength locker according to claim 13, further comprising a plurality of photodetectors configured to convert the light output from the plurality of outputs of the second MMI coupler to the plurality of signals for the interference pattern selector.