# US 2022/0045475 A1 · System and method for frequency matching a resonance cavity to a light source

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- Number: US 2022/0045475 A1
- Document ID: US20220045475A1
- Status: Published application
- Kind: A1
- Application number: 16/984,740
- Filed: 2020-08-04
- Published: 2022-02-10
- Earliest claimed: 2020-08-04
- Assignees: Picomole Inc.
- Applicants: Picomole Inc.
- Inventors: Sébastien NOËL; Jean-François BISSON; Alexis GAUVIN; Alexandre DOUCET; Gisia BEYDAGHYAN
- Web page: https://patentgrep.com/patent/US20220045475A1

## CPC

- G01N 21/0303: {Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment (G01N21/031 - G01N21/15 take precedence)}
- H01S 3/1303: {by using a passive reference, e.g. absorption cell (H01S3/139 takes precedence)}
- G01J 3/027: {Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation}
- G01J 3/0297: {Constructional arrangements for removing other types of optical noise or for performing calibration}
- G01J 3/108: {for measurement in the infrared range}
- G01J 3/42: Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry (beam switching arrangements G01J3/08)
- G01N 21/031: {Multipass arrangements}
- G01N 21/39: using tunable lasers
- G01N 21/61: Non-dispersive gas analysers {(G01N21/3504 takes precedence)}
- H01S 3/10: Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S 5/141: {using a wavelength selective device, e.g. a grating or etalon (H01S5/146 takes precedence)}
- G01J 2003/104: {Monochromatic plural sources}
- H01S 3/005: {Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping (shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B)}
- H01S 3/0071: {Beam steering, e.g. whereby a mirror outside the cavity is present to change the beam direction}
- H01S 3/2232: {Carbon dioxide (CO2) or monoxide [CO]}
- H01S 3/2391: {emitting at different wavelengths}
- H10N 30/20: with electrical input and mechanical output, e.g. functioning as actuators or vibrators
- H10N 30/802: {Circuitry or processes for operating piezoelectric or electrostrictive devices not otherwise provided for, e.g. drive circuits}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- 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
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A method and system for frequency matching a resonant cavity is disclosed. Light is received in a resonant cavity having at least a first mirror and a second mirror defining a path along which light is reflected. At least the second mirror is actuatable to vary the length of the path of the resonant cavity. An intensity of the light exiting or reflecting from the resonant cavity is monitored, and an error correction is determined. The second mirror is actuated towards a pose relative to the first mirror at which a frequency of the light is in resonance with the length of the path. In this manner, the resonant cavity is frequency matched to the light to maintain the resonant cavity in resonance.

## Claims

### Claim 1

A method for frequency matching a resonant cavity, comprising:
receiving light in a resonant cavity, the resonant cavity having at least a first mirror and a second mirror defining a path along which light is reflected, one or both of the first mirror and the second mirror at least partially permitting light from the resonant cavity to pass therethrough, at least the second mirror being actuatable to vary the length of the path of the resonant cavity;
monitoring an intensity of the light exiting or reflecting from the resonant cavity via the at least one of the first mirror and the second mirror;
determining an error correction from the monitored intensity of the light from the resonant cavity; and
actuating the second mirror towards a pose relative to the first mirror at which a frequency of the light is in resonance with the length of the path.

### Claim 2 (depends on 1)

The method of claim 1, wherein the first mirror is positioned at a first end of the resonant cavity, the second mirror is positioned at a second end of the resonant cavity, and the path is defined between the first mirror and the second mirror.

### Claim 3 (depends on 1)

The method of claim 1, wherein the light is infrared or near-infrared.

### Claim 4 (depends on 1)

The method of claim 1, wherein the second mirror is actuated to move at least one of towards or away from the first mirror to determine a directionality of an error correction to be applied to the second mirror.

### Claim 5 (depends on 4)

The method of claim 4, wherein the second mirror is constantly actuated to alternatingly move towards and away from the first mirror to determine the error correction.

### Claim 6 (depends on 4)

The method of claim 4, wherein the second mirror is intermittently actuated to move at least one of towards and away from the first mirror to determine the error correction.

### Claim 7 (depends on 4)

The method of claim 4, wherein the second mirror is alternatingly unactuated when a ring-down event is occurring and oscillated in between ring-down events.

### Claim 8 (depends on 4)

The method of claim 4, further comprising receiving the light in the resonant cavity via the first mirror.

### Claim 9 (depends on 8)

The method of claim 8, wherein the monitoring is performed by a photosensor positioned to monitor light exiting the resonant cavity via the second mirror.

### Claim 10 (depends on 8)

The method of claim 8, wherein the monitoring is performed by a photosensor positioned to monitor light reflected from the first mirror and/or exiting the resonant cavity via the first mirror.

### Claim 11

A system for frequency matching a resonant cavity, comprising:
a resonant cavity having at least a first mirror and a second mirror defining a path along which light is reflected, one or both of the first mirror and the second mirror at least partially permitting light from the resonant cavity to pass therethrough, at least the second mirror being actuatable to vary the length of the path of the resonant cavity;
a light intensity meter configured to monitor an intensity of the light exiting or reflecting from the resonant cavity via the at least one of the first mirror and the second mirror;
a logic unit configured to determine an error correction from the intensity of the light monitored by the light intensity meter; and
a mirror actuator system configured to actuate the second mirror, at least partially based on the error correction, towards a pose relative to the first mirror at which a frequency of the light is in resonance with the length of the path.

### Claim 12 (depends on 11)

The system of claim 11, wherein the mirror actuator system comprises at least one piezo-electric actuator connected to the logic unit.

### Claim 13 (depends on 11)

The system of claim 11, wherein the first mirror is positioned at a first end of the resonant cavity, the second mirror is positioned at a second end of the resonant cavity, and the path is defined between the first mirror and the second mirror.

### Claim 14 (depends on 11)

The system of claim 11, wherein the light is infrared or near-infrared.

### Claim 15 (depends on 11)

The system of claim 11, wherein the second mirror is actuated to move at least one of towards or away from the first mirror to determine a directionality of an error correction to be applied to the first mirror.

### Claim 16 (depends on 15)

The system of claim 15, wherein the second mirror is constantly actuated to alternatingly move towards and away from the first mirror to determine the error correction.

### Claim 17 (depends on 15)

The system of claim 15, wherein the second mirror is intermittently actuated to move at least one of towards and away from the first mirror to determine the error correction.

### Claim 18 (depends on 15)

The system of claim 15, wherein the second mirror is alternatingly unactuated when a ring-down event is occurring and oscillated in between ring-down events.

### Claim 19 (depends on 15)

The system of claim 15, further comprising a light system configured to deliver the light into the resonant cavity via the first mirror.

### Claim 20 (depends on 19)

The system of claim 19, further comprising a photosensor positioned to monitor light exiting the resonant cavity via the second mirror.

### Claim 21 (depends on 19)

The system of claim 19, further comprising a photosensor positioned to monitor light reflected from the first mirror and/or exiting the resonant cavity via the first mirror.