# US 9,753,224 B2 · Field-programmable optical component

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

- Number: US 9,753,224 B2
- Document ID: US9753224B2
- Status: Granted
- Kind: B2
- Application number: 15/080,170
- Filed: 2016-03-24
- Published: 2017-02-02
- Granted: 2017-09-05
- Earliest claimed: 2015-03-25
- Assignees: The Board of Trustees of the Leland Stanford Junior University
- Applicants: The Board of Trustees of the Leland Stanford Junior University
- Inventors: David A. B. Miller
- Web page: https://patentgrep.com/patent/US9753224B2

## CPC

- G02B 6/29395: {configurable, e.g. tunable or reconfigurable (switching G02B6/35)}
- G01B 9/02015: characterised by the beam path configuration
- G01B 9/02075: {of particular errors}
- G02B 6/2935: {Mach-Zehnder configuration, i.e. comprising separate splitting and combining means}
- G02B 6/29355: {Cascade arrangement of interferometers}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS

## Abstract

Methods are known for implementing general optical functions using wave splitters. However, these methods rely on these wave splitters having maximal extinction ratio, which is difficult to achieve in practice. The present invention provides methods for automatically adjusting wave splitters to provide maximal extinction ratio.

## Claims

### Claim 1

A method for adjusting an interferometer to have maximum extinction ratio, the method comprising:
providing an interferometer comprising a first wave splitter having an input I1-1 and having outputs O1-1 and O1-2, a phase adjuster, and a second wave splitter having inputs I2-1 and I2-2 and having outputs O2-1 and O2-2;
wherein O1-1 is connected to I2-1 and O1-2 is connected to I2-2, wherein the phase adjuster provides a relative phase θ between these two connections;
wherein the first wave splitter has an adjustable first split error E1=R1−½, wherein R1 is a power transmittance from I1-1 to O1-1;
wherein the second wave splitter has an adjustable second split error E2=R2−½, wherein R2 is a power transmittance from I2-1 to O2-1;
wherein the interferometer has a bar state where θ is selected to maximize transmission from I1-1 to O2-1 relative to transmission from I1-1 to O2-2;
wherein the interferometer has a cross state where θ is selected to maximize transmission from I1-1 to O2-2 relative to transmission from I1-1 to O2-1;
performing an automatic adjustment that includes an alternating sequence of the following steps:
i) adjusting E1 and E2 to optimize cross state performance, wherein changes to E1 and E2 are linked such that their values change by substantially equal amounts;
ii) adjusting E1 and E2 to optimize bar state performance, wherein changes to E1 and E2 are linked such that their values change by substantially equal and opposite amounts.

### Claim 2

Optical apparatus comprising:
an interferometer comprising a first wave splitter having an input I1-1 and having outputs O1-1 and O1-2, a phase adjuster, and a second wave splitter having inputs I2-1 and I2-2 and having outputs O2-1 and O2-2;
wherein O1-1 is connected to I2-1 and O1-2 is connected to I2-2, wherein the phase adjuster provides a relative phase θ between these two connections;
wherein the first wave splitter has an adjustable first split error E1=R1−½, wherein R1 is a power transmittance from I1-1 to O1-1;
wherein the second wave splitter has an adjustable second split error E2=R2−½, wherein R2 is a power transmittance from I2-1 to O2-1;
wherein the interferometer has a bar state where θ is selected to maximize transmission from I1-1 to O2-1 relative to transmission from I1-1 to O2-2;
wherein the interferometer has a cross state where θ is selected to maximize transmission from I1-1 to O2-2 relative to transmission from I1-1 to O2-1;
wherein the apparatus is configured to perform an automatic adjustment that includes an alternating sequence of the following steps:
i) adjusting E1 and E2 to optimize cross state performance, wherein changes to E1 and E2 are linked such that their values change by substantially equal amounts;
ii) adjusting E1 and E2 to optimize bar state performance, wherein changes to E1 and E2 are linked such that their values change by substantially equal and opposite amounts.

### Claim 3 (depends on 2)

The apparatus of claim 2, wherein the first wave splitter comprises a waveguide Mach-Zehnder interferometer having a fabricated split ratio in a range from 15:85 to 85:15.

### Claim 4 (depends on 2)

The apparatus of claim 2, wherein the second wave splitter comprises a waveguide Mach-Zehnder interferometer having a fabricated split ratio in a range from 15:85 to 85:15.

### Claim 5 (depends on 2)

The apparatus of claim 2, further comprising a tap detector configured to monitor power emitted from O2-1.

### Claim 6 (depends on 2)

The apparatus of claim 2, further comprising a tap detector configured to monitor power emitted from O2-2.

### Claim 7 (depends on 2)

The apparatus of claim 2, wherein the apparatus is configured to automatically halt the alternating sequence of the steps (i) and (ii) when a stopping condition is satisfied.

### Claim 8 (depends on 7)

The apparatus of claim 7, wherein the stopping condition is reaching a predetermined maximum number of iterations.

### Claim 9 (depends on 7)

The apparatus of claim 7, wherein the stopping condition is measure power going below a predetermined minimum power threshold during power minimization.

### Claim 10 (depends on 7)

The apparatus of claim 7, wherein the stopping condition is having a change in measured power between two successive iterations be below a predetermined threshold during power maximization.

### Claim 11 (depends on 2)

The apparatus of claim 2, wherein the first wave splitter has an input I1-2.