# US 7,123,800 B2 · Integrated loop resonator with adjustable couplings and methods of using the same

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- Number: US 7,123,800 B2
- Document ID: US7123800B2
- Status: Granted
- Kind: B2
- Application number: 11/069,917
- Filed: 2005-02-28
- Published: 2005-09-08
- Granted: 2006-10-17
- Earliest claimed: 2004-03-02
- Assignees: CeLight, Inc.
- Inventors: Arkady Kaplan
- Web page: https://patentgrep.com/patent/US7123800B2

## CPC

- H01S 3/0632: {Thin film lasers in which light propagates in the plane of the thin film}
- G02B 6/12007: {forming wavelength selective elements, e.g. multiplexer, demultiplexer}
- G02F 1/3132: {of directional coupler type}
- G02F 2203/15: involving resonance effects, e.g. resonantly enhanced interaction
- H01S 3/083: Ring lasers {(fibre ring lasers H01S3/06791)}
- 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
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

An integrated optical device with a loop resonator is provided, having at least one closed waveguiding loop which has losses. A coupler and at least one input waveguide is coupled to the loop resonator, An adjustment unit controls a coupling coefficient K1 of the coupler, and a second coupler is coupled to the loop resonator. At least one output waveguide is coupled with the second coupler to the loop resonator. Another adjustment unit is configured to control coupling coefficient K2 of the second coupler, being related to the value of K1, accordingly to the following equation K2=f{K1,ξ}, providing Q{K2}=Max {Q}, where (1−ξ) are the total optical losses within the loop resonator and Q is a resonator characteristic.

## Claims

### Claim 1

An integrated optical device, comprising:
a loop resonator with at least one closed waveguiding loop, the loop resonator having losses;
a coupler coupled to the loop resonator;
at least one input waveguide coupled with a first coupler to the loop resonator;
a first adjustment unit to control a coupling coefficient K1 of the first coupler;
a second coupler coupled to the loop resonator; and
at least one output waveguide coupled with the second coupler to the loop resonator,
the second adjustment unit configured to control a coupling coefficient K2 of the second coupler, being related to the value of K1, accordingly to the following equation
K2=f{K1,ξ}, providing Q{K2}=Max {Q},
where (1−ξ) are the total optical losses within the loop resonator and Q is a resonator characteristic.

### Claim 2 (depends on 1)

The integrated optical device of claim 1, wherein the resonator characteristic Q is selected from at least one of, a resonator contrast, a resonator quality-factor, a resonator finesse, and a spectral line-width.

### Claim 3 (depends on 1)

The integrated optical device of claim 1, wherein the first and the second couplers are of different types, and selected from at least one of, electro-optical, thermo-optical, acousto-optical, and opto-mechanical couplers.

### Claim 4 (depends on 1)

The integrated optical device of claim 1, wherein the first and the second couplers have different operating characteristics.

### Claim 5 (depends on 1)

The integrated optical device of claim 1, further comprising:
a phase shifter incorporated in the loop resonator, the phase shifter configured to introduce a variable optical phase change ΔΦ into a wave, propagating within the loop resonator.

### Claim 6 (depends on 5)

The integrated optical device of claim 5, wherein the variable phase change ΔΦ is related to the to the values of K1 and K2 accordingly to the following equation
ΔΦ=f{K2,K2,ξ} for Q{ΔΦ}=Max{Q}.

### Claim 7 (depends on 4)

The integrated optical device of claim 4, wherein the phase shifter is one or more than one separate units located at different positions of the loop resonator.

### Claim 8 (depends on 7)

The integrated optical device of claim 7, wherein the separate units of the phase shifter are the same.

### Claim 9 (depends on 7)

The integrated optical device of claim 7, wherein the separate units of the phase shifter are different.

### Claim 10 (depends on 7)

The integrated optical device of claim 7, wherein at least one phase shifter is a modulator with operating frequency from 0 Hz to 1 GHz.

### Claim 11 (depends on 7)

The integrated optical device of claim 7, wherein at least one phase shifter is a modulator with operating frequency from 1 GHz to 150 GHz.

### Claim 12 (depends on 7)

The integrated optical device of claim 7, wherein at least one phase shifter is a traveling-wave type of electro-optical modulator.

### Claim 13 (depends on 7)

The integrated optical device of claim 7, wherein at least one phase shifter is a resonator type of electro-optical modulator.

### Claim 14 (depends on 4)

The integrated optical device of claim 4, wherein the phase shifter is at least one modulator selected from, electro-optical, thermo-optical, acousto-optical and opto-mechanical.

### Claim 15 (depends on 1)

The integrated optical device of claim 1, wherein the loop resonator includes two rings coupled to each other with a third coupler.

### Claim 16 (depends on 15)

The integrated optical device of claim 15, further comprising a third adjustment unit to control the coupling parameter of the third coupler and having a value K3 according to following equation:
K3=f{K1,K2,ξ} for Q{K3}=Max{Q}.

### Claim 17 (depends on 1)

The integrated optical device of claim 1, wherein the loop resonator includes N rings coupled to each other with (N−1) couplers and N is an integer number larger than 3.

### Claim 18 (depends on 1)

The integrated optical device of claim 1, wherein the loop resonator includes at least one reflection element.

### Claim 19 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is integrated in a lithium niobate electro-optical crystal.

### Claim 20 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is integrated in a lithium tantalite electro-optical crystal.

### Claim 21 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is integrated in a material with optical gain.

### Claim 22 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is integrated in a semiconductor material selected from GaAs, InP, and Si.

### Claim 23 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is integrated on silica.

### Claim 24 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is configured to produce an output wave with a set of frequencies equidistantly apart from each other.

### Claim 25 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is configured to produce a laser output.

### Claim 26 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is configured to produce a modulated output light.

### Claim 27 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is configured to produce a tunable filtering of light.

### Claim 28 (depends on 1)

The integrated optical device of claim 1, wherein the integrated optical device is configured to produce a sensing of at least one external parameter.

### Claim 29 (depends on 28)

The integrated optical device of claim 28, wherein the external parameters include at least one of, temperature, material concentration and angle velocity of an interrogated object.

### Claim 30

A method for creating an integrated optical device, comprising:
providing a loop resonator that has losses;
coupling the loop resonator to an input and output waveguides with a first and a second couplers;
incorporating a first and second adjustment units to the first and the second couplers;
driving the first and the second adjustment units independently;
driving the second adjustment unit to control a coupling coefficient K2 of the second coupler, being related to the value of a coupling coefficient K1 of the first coupler, accordingly to the following equation
K2=f{K1,ξ}, providing Q{K2}=Max{Q},
where (1−ξ) are the total optical losses within the loop resonator and Q is a resonator characteristic.

### Claim 31 (depends on 30)

The method of claim 30, wherein the resonator characteristic Q is selected from at least one of, a resonator contrast, a resonator quality-factor, a resonator finesse, and a spectral line-width.

### Claim 32 (depends on 30)

The method of claim 30, further comprising:
integrating the gain element in the loop resonator; and
maximizing the characteristic Q for the laser beam generation output.

### Claim 33 (depends on 30)

The method of claim 30, wherein characteristic Q is maximized for the filtering of the optical beam with a predetermined spectral selectivity.

### Claim 34 (depends on 30)

The method of claim 30, further comprising: integrating at least one phase shifter in the loop resonator.

### Claim 35 (depends on 34)

The method of claim 34, wherein the characteristic Q is maximized for generation of modulated light beam output.

### Claim 36 (depends on 34)

The method of claim 34, wherein characteristic Q is maximized for generation of an output with a set of optical frequencies equidistantly apart from each other.

### Claim 37 (depends on 34)

The method of claim 34, wherein characteristic Q is maximized for generation of an optical output with an optical phase encoded with the information on at least one external parameter.

### Claim 38 (depends on 30)

The method of claim 30, wherein the external parameters include at least one of, temperature, material concentration and angle velocity of an interrogated object.