# US 11,658,462 B2 · Integrated filter remote gas correlation sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,658,462 B2 - Document ID: US11658462B2 - Status: Granted - Kind: B2 - Application number: 16/879,658 - Filed: 2020-05-20 - Published: 2021-11-25 - Granted: 2023-05-23 - Earliest claimed: 2020-05-20 - Assignees: National Research Council of Canada - Applicants: National Research Council of Canada - Inventors: Ross Cheriton; Siegfried Janz; Adam Densmore - Web page: https://patentgrep.com/patent/US11658462B2 ## CPC - G01N 21/3504: for analysing gases, e.g. multi-gas analysis - H01S 5/142: {which comprises an additional resonator} - H01S 5/026: Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers (stabilisation of output H01S5/06) - H01S 5/0612: {controlled by temperature} - G01N 2021/3509: {Correlation method, e.g. one beam alternating in correlator/sample field} - G01N 2021/3531: {without instrumental source, i.e. radiometric} - 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 ## Abstract An integrated optical sensor enables the detection and identification of one or more remote gases using a transmission filter that matches specific absorption features of a remote gas and is detected using a single photodetection element. The sensor comprises an integrated optical component that is characterized by its transmission spectrum which corresponds to absorption or emission features of a target gas over a defined spectral bandpass, and the ability to have a reversibly tunable transmission spectrum. The change in the optical power output from the sensor as the transmission spectrum is tuned is proportional to the optical depth of the target gas absorption lines when viewed with a background light source. The optical power output from the integrated optical component is therefore related to the absorption spectrum of the input light Physical properties of the sensor are tailored to produce a quasi-periodic transmission spectrum that results in a stronger signal contrast for a specific gas. The sensor is preferably a waveguide ring resonator with a free spectral range that matches the absorption spectrum of a gas over a finite spectral bandpass. ## Claims ### Claim 1 An apparatus, comprising: an optical waveguide ring resonator having a waveguide width and height; a well-defined round-trip length that results in a free spectral range matching spacing of spectral features of a remote target over a defined bandpass; a bandpass filter; a background light source; a singular or plurality of optical bus waveguides evanescently coupled to the ring resonator; input and output optical channels; an active element which can reversibly tune the effective index of the ring resonator; and a photodetector. ### Claim 2 (depends on 1) The apparatus as in claim 1, wherein the input and output channels comprise at least one of single mode waveguides, single mode optical fibers, focusing and/or collimating objectives, or surface grating couplers or optical antennae. ### Claim 3 (depends on 1) The apparatus as in claim 1, wherein the spectral features are absorption features, emission features, molecular in nature or atomic in nature. ### Claim 4 (depends on 1) The apparatus as in claim 1, wherein the input light into the ring resonator is polarized to the TE polarization or to the TM polarization. ### Claim 5 (depends on 1) The apparatus as in claim 1, wherein the input light is divided by polarization and input into two ring separate ring resonators. ### Claim 6 (depends on 1) The apparatus as in claim 1, wherein the ring resonator transmission spectrum matches one of more spectral features of a single gas or multiple gases. ### Claim 7 (depends on 1) The apparatus as in claim 1, wherein the ring resonator is in an add-drop configuration. ### Claim 8 (depends on 1) The apparatus as in claim 1, wherein the output light is measured from a drop port of a ring resonator or a through-port of a ring resonator. ### Claim 9 (depends on 1) The apparatus as in claim 1, wherein the ring resonator is in a racetrack geometry, a spiral geometry, a circular geometry, or an arbitrary closed loop geometry. ### Claim 10 (depends on 1) The apparatus as in claim 1, wherein the ring resonator is a multitude of ring resonators in series or parallel. ### Claim 11 (depends on 1) The apparatus as in claim 1, wherein the waveguide of the ring resonator is a slot waveguide, subwavelength grating waveguide, a strip loaded waveguide, a photonic crystal waveguide, a buried waveguide, an arrow waveguide, a ridge waveguide. ### Claim 12 (depends on 1) The apparatus as in claim 1, wherein the output signal is measured using a lock-in amplifier. ### Claim 13 (depends on 1) The apparatus as in claim 1, wherein the photodetector comprises a single channel element or an array of detection elements. ### Claim 14 (depends on 1) The apparatus as in claim 1, wherein the evanescently coupled optical bus and ring waveguides are directional couplers or multimode interference couplers. ### Claim 15 (depends on 1) The apparatus as in claim 1, wherein the active element comprises: a patterned microheater with a current source or a voltage source; a temperature-controlled package in thermal contact with the chip; a semiconductor junction for charge injection or an electric field modulator. ### Claim 16 (depends on 1) The apparatus as in claim 1, wherein the bandpass filter has a tunable bandwidth or a tunable center bandwidth. ### Claim 17 (depends on 1) The apparatus as in claim 1, wherein the bandpass filter is integrated on-chip or is a bulk optical element. ### Claim 18 (depends on 1) A method, comprising providing the ring resonator of the apparatus of claim 1 with a free spectral range that matches a spectral feature spacing of a remote gas target over a defined bandpass. ### Claim 19 A gas sensor for the detection of a target gas located remotely from the gas sensor and between a light source and the gas sensor, the target gas having a target gas absorption spectrum, comprising: a loop resonator comprising an input for receiving an input signal and an output for outputting an output signal having an output signal transmission spectrum, wherein a transmission spectrum of the input signal includes the gas absorption spectrum, the loop resonator having at least one length dependent on a characteristic of the target gas absorption spectrum; and a heating element providing an adjustable range of current to the loop resonator, wherein temperature modulation of the loop resonator causes a spectral shift of resonances in the output signal transmission spectrum permitting tuning of the loop resonator to match at least one spectral feature of the target gas absorption spectrum.