# US 10,483,717 B2 · Laser power adjustment during tuning to compensate for detector response and varying background absorption

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- Number: US 10,483,717 B2
- Document ID: US10483717B2
- Status: Granted
- Kind: B2
- Application number: 16/160,822
- Filed: 2018-10-15
- Published: 2019-05-02
- Granted: 2019-11-19
- Earliest claimed: 2017-11-01
- Assignees: Daylight Solutions, Inc.
- Applicants: Daylight Solutions, Inc.
- Inventors: Miles James Weida; William Chapman; Bruce Coy
- Web page: https://patentgrep.com/patent/US10483717B2

## CPC

- H01S 5/0683: by monitoring the optical output parameters
- G01J 3/10: Arrangements of light sources specially adapted for spectrometry or colorimetry
- G01J 3/108: {for measurement in the infrared range}
- G01J 3/433: Modulation spectrometry; Derivative spectrometry
- G01N 21/00: Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light (G01N3/00 - G01N19/00 take precedence)
- G01N 21/39: using tunable lasers
- H01S 5/02407: {Active cooling, e.g. the laser temperature is controlled by a thermo-electric cooler or water cooling}
- H01S 5/02453: {Heating, e.g. the laser is heated for stabilisation against temperature fluctuations of the environment (H01S5/0612 takes precedence, for monolithically integrated heaters see also H01S5/0261)}
- H01S 5/02469: {Passive cooling, e.g. where heat is removed by the housing as a whole or by a heat pipe without any active cooling element like a TEC}
- H01S 5/0261: {Non-optical elements, e.g. laser driver components, heaters (H01S5/0265 takes precedence)}
- H01S 5/0264: {for monitoring the laser-output}
- H01S 5/0612: {controlled by temperature}
- H01S 5/06804: {by monitoring an external parameter, e.g. temperature}
- H01S 5/06808: {by monitoring the electrical laser parameters, e.g. voltage or current}
- H01S 5/06817: {Noise reduction}
- H01S 5/06837: {Stabilising otherwise than by an applied electric field or current, e.g. by controlling the temperature}
- H01S 5/1092: {Multi-wavelength lasing}
- G01J 2003/4332: {frequency-modulated}
- G01J 2003/4334: {by modulation of source, e.g. current modulation}
- H01S 5/02415: {by using a thermo-electric cooler [TEC], e.g. Peltier element}
- H01S 5/028: Coatings {; Treatment of the laser facets, e.g. etching, passivation layers or reflecting layers}
- H01S 5/0287: {Facet reflectivity}
- H01S 5/14: External cavity lasers (H01S5/18 takes precedence; mode locking H01S5/065)
- H01S 5/141: {using a wavelength selective device, e.g. a grating or etalon (H01S5/146 takes precedence)}
- H01S 5/3401: {having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers}
- H01S 2301/02: ASE (amplified spontaneous emission), noise; Reduction thereof
- 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)
- 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)

## Abstract

An assembly (14) for analyzing a sample (15) includes a detector assembly (18); a tunable laser assembly (10); and (iii) a laser controller (10F). The detector assembly (18) has a linear response range (232) with an upper bound (232A) and a lower bound (232B). The tunable laser assembly (10) is tunable over a tunable range, and includes a gain medium (10B) that generates an illumination beam (12) that is directed at the detector assembly (18). The laser controller (10F) dynamically adjusts a laser drive to the gain medium (10B) so that the illumination beam (12) has a substantially constant optical power at the detector assembly (18) while the tunable laser assembly (10) is tuned over at least a portion of the tunable range.

## Claims

### Claim 1

An assembly for analyzing a sample, the assembly comprising:
a detector assembly having a linear response range with an upper bound and a lower bound;
a tunable laser assembly that is tunable over a tunable range, the tunable laser assembly including a gain medium that generates an illumination beam that is directed at the detector assembly; and
a laser controller that dynamically adjusts a laser drive to the gain medium so that the illumination beam has a substantially constant optical power at the detector assembly while the tunable laser assembly is tuned over at least a portion of the tunable range.

### Claim 2 (depends on 1)

The assembly of claim 1 wherein the laser controller dynamically adjusts the laser drive to the gain medium so that the illumination beam has a substantially constant optical power at the detector assembly while the tunable laser assembly is tuned over at least seventy percent of the tunable range.

### Claim 3 (depends on 1)

The assembly of claim 1 wherein the laser controller dynamically adjusts the laser drive to the gain medium so that the illumination beam has a substantially constant optical power at the detector assembly while the tunable laser assembly is tuned over at least eighty percent of the tunable range.

### Claim 4 (depends on 1)

The assembly of claim 1 wherein the laser controller dynamically adjusts the laser drive to the gain medium so that the illumination beam has a substantially constant optical power at the detector assembly while the tunable laser assembly is tuned over at least ninety percent of the tunable range.

### Claim 5 (depends on 1)

The assembly of claim 1 wherein the laser controller dynamically adjusts the laser drive to the gain medium so that optical power of the illumination beam at the detector assembly is within approximately seventy percent of the upper bound of the linear response range for at least a seventy percent of the tunable range.

### Claim 6 (depends on 1)

The assembly of claim 1 wherein the laser controller dynamically adjusts the laser drive to the gain medium so that optical power of the illumination beam at the detector assembly is within approximately eighty percent of the upper bound of the linear response range for at least eighty percent of the tunable range.

### Claim 7 (depends on 1)

The assembly of claim 1 wherein the laser controller dynamically adjusts the laser drive to the gain medium as a function of wavelength so that optical power of the illumination beam at the detector assembly is within approximately ninety percent of the upper bound of the linear response range for at least ninety percent of the tunable range.

### Claim 8 (depends on 1)

The assembly of claim 1 wherein the laser controller dynamically adjusts the laser drive to the gain medium so that optical power of the illumination beam at the detector assembly is optimized for maximum linear response and minimum noise contribution as the laser assembly is tuned over a portion of the tunable range.

### Claim 9 (depends on 1)

The assembly of claim 1 wherein the laser controller dynamically adjusts the laser drive to the gain medium as a function of wavelength to compensate for at least one of sample absorption and background absorption around the sample.

### Claim 10 (depends on 1)

The assembly of claim 1 further comprising a temperature management system that is in thermal communication with the gain medium, and a thermal compensator positioned near the gain medium, wherein the laser controller dynamically adjusts a compensator drive to the thermal compensator to maintain a substantially constant thermal load on the temperature management system as the laser assembly is tuned over the tunable range.

### Claim 11 (depends on 10)

The assembly of claim 10 wherein the laser controller dynamically adjusts the compensator drive command to the thermal compensator to dynamically maintain the medium temperature so that the medium temperature varies less than one degree Celsius during the tuning of the laser assembly.

### Claim 12 (depends on 10)

The assembly of claim 10 further comprising a heat sink that thermally connects the gain medium and the thermal compensator to the thermal management system, wherein the laser controller dynamically adjusts the compensator drive command to the thermal compensator to dynamically maintain a sink temperature of the heat sink so that the sink temperature varies less than one degree Celsius during the tuning of the laser assembly.

### Claim 13 (depends on 1)

The assembly of claim 1 further comprising a thermal compensator positioned near the gain medium, wherein the laser controller dynamically adjusts a compensator drive to the thermal compensator to ensure a substantially constant net thermal load during the tuning of the laser assembly.

### Claim 14 (depends on 13)

The assembly of claim 13 wherein the laser controller dynamically adjusts the compensator drive to the thermal compensator in a wavelength varying manner to compensate for the changes in thermal load from the gain medium that result from matching the optical power to the detectors or compensating for an absorbing sample or optical material background absorption.

### Claim 15

A method for analyzing a sample comprising:
providing a detector assembly having a linear response range with an upper bound and a lower bound;
generating an illumination beam that is directed at the detector assembly with a gain medium of a tunable laser assembly that is tunable over a tunable range; and
dynamically adjusting a laser drive to the gain medium with a laser controller so that the illumination beam has a substantially constant optical power at the detector assembly while the tunable laser assembly is tuned over at least a portion of the tunable range.

### Claim 16

An assembly comprising:
a temperature management system;
a tunable laser assembly that is tunable over a tunable range, the tunable laser assembly including a gain medium that generates an illumination beam that is directed at the detector assembly, and a thermal compensator positioned near the gain medium, wherein the gain medium and the thermal compensator are in thermal communication with the temperature management system; and
a laser controller that dynamically adjusts a laser drive to the gain medium as a function of wavelength, and that dynamically adjusts a compensator drive to the thermal compensator to dynamically control a thermal load on the temperature management system as the laser assembly is tuned over the tunable range.

### Claim 17 (depends on 16)

The assembly of claim 16 further comprising a detector assembly and wherein the laser controller dynamically adjusts the laser drive to the gain medium so that the illumination beam has a substantially constant optical power at the detector assembly while the tunable laser assembly is tuned over at least a portion of the tunable range.

### Claim 18 (depends on 16)

The assembly of claim 16 wherein the thermal compensator includes a heat generating element.

### Claim 19 (depends on 16)

The assembly of claim 16 wherein the thermal compensator has a compensator thermal time constant that is approximately equal to a medium thermal time constant of the gain medium.

### Claim 20 (depends on 16)

The assembly of claim 16 wherein the laser controller dynamically adjusts the laser drive to the gain medium as a function of wavelength to compensate for at least one of sample absorption and background absorption around the sample.

### Claim 21 (depends on 16)

The assembly of claim 16 wherein the laser controller dynamically adjusts the compensator drive to the thermal compensator to dynamically maintain the medium temperature so that the medium temperature varies less than one degree Celsius during the tuning of the laser assembly.

### Claim 22

A method for analyzing a sample comprising:
generating an illumination beam that is directed at the sample with a gain medium of a tunable laser assembly that is tunable over a tunable range;
positioning a thermal compensator near the gain medium;
thermally connecting the gain medium and the thermal compensator to a temperature management system;
dynamically adjusting a laser drive to the gain medium with a laser controller as a function of wavelength; and
dynamically adjusting a compensator drive to the thermal compensator to dynamically control a thermal load on the temperature management system as the laser assembly is tuned over the tunable range.