A dual-comb spectrometer comprising two lasers outputting respective frequency combs having a frequency offset between their intermode beat frequencies. One laser acts as a master and the other as a follower. Although the master laser is driven nominally with a DC drive signal, the current on its drive input line nevertheless oscillates with an AC component that follows the beating of the intermode comb lines lasing in the driven master laser. This effect is exploited by tapping off this AC component and mixing it with a reference frequency to provide the required frequency offset, the mixed signal then being supplied to the follower laser as the AC component of its drive signal. The respective frequency combs in the optical domain are thus phase-locked relative to each other in one degree of freedom, so that the electrical signals obtained by multi-heterodyning the two optical signals are frequency stabilized.

A dual-comb spectrometer comprising two lasers outputting respective frequency combs having a frequency offset between their intermode beat frequencies. One laser acts as a master and the other as a follower. Although the master laser is driven nominally with a DC drive signal, the current on its drive input line nevertheless oscillates with an AC component that follows the beating of the intermode comb lines lasing in the driven master laser. This effect is exploited by tapping off this AC component and mixing it with a reference frequency to provide the required frequency offset, the mixed signal then being supplied to the follower laser as the AC component of its drive signal. The respective frequency combs in the optical domain are thus phase-locked relative to each other in one degree of freedom, so that the electrical signals obtained by multi-heterodyning the two optical signals are frequency stabilized.

A method for retrieving a corrected spectrum from a measured spectrum (e.g., retrieving a top-of-water spectrum from a measured top-of-atmosphere spectrum) includes creating a scene-specific model of a region of interest and performing a ray-tracing simulation to simulate rays of light that would reach an airborne (or spaceborne) sensor. The region of interest can be an optically complex area such as an inland or coastal body of water. Based on the ray-tracing simulation, a scene-specific correction for unwanted effects (e.g., adjacency effects, variable atmospheric conditions, and/or other suitable effects) is obtained. A corrected spectrum is obtained by correcting the measured spectrum using the scene-specific correction. The ray-tracing simulation may be performed using a graphical processing unit, allowing the scene-specific correction to be performed in real time or near real time.

Provided is a system for measuring gas temperature and component concentrations in a combustion field based on optical comb. The system includes two pulse laser devices, two continuous laser devices, a beam splitting device, a measurement path, an interference signal detecting device, an optical processing and electrical processing device and a signal acquisition and analysis device. The measurement path refers to the combustion field to be measured. The interference signal detecting device outputs an interference signal. The optical processing and electrical processing device includes several optic elements and electrical elements, and outputs an adaptive compensation signal and an asynchronous sampling clock signal after a series of processing on output of the two pulse laser devices and two continuous laser devices. The signal acquisition and analysis device outputs the measurement result based on the adaptive compensation signal, the asynchronous sampling clock signal and a stable interference signal.

A gas analysis system, includes: a light-emitting element that emits a laser light modulated by a predetermined modulation frequency; and a light-receiving element that: receives the laser light that has passed through a measurement target gas; and upon receiving the laser light, outputs a received signal having an N-frequency that is n times the predetermined modulation frequency, wherein n is an integer no less than 2; and a signal processing device that: calculates a third component by removing, from a first component having the N-frequency, a second component, wherein the second component is a component of optical interference noise arising on an optical path of the laser light from the light-emitting element to the light-receiving element and has the same frequency as the first component; and calculates, based on a magnitude of the third component, a concentration of the measurement target gas.

This relates to systems and methods for measuring a concentration and type of substance in a sample at a sampling interface. The systems can include a light source, optics, one or more modulators, a reference, a detector, and a controller. The systems and methods disclosed can be capable of accounting for drift originating from the light source, one or more optics, and the detector by sharing one or more components between different measurement light paths. Additionally, the systems can be capable of differentiating between different types of drift and eliminating erroneous measurements due to stray light with the placement of one or more modulators between the light source and the sample or reference. Furthermore, the systems can be capable of detecting the substance along various locations and depths within the sample by mapping a detector pixel and a microoptics to the location and depth in the sample.

This relates to systems and methods for measuring a concentration and type of substance in a sample at a sampling interface. The systems can include a light source, optics, one or more modulators, a reference, a detector, and a controller. The systems and methods disclosed can be capable of accounting for drift originating from the light source, one or more optics, and the detector by sharing one or more components between different measurement light paths. Additionally, the systems can be capable of differentiating between different types of drift and eliminating erroneous measurements due to stray light with the placement of one or more modulators between the light source and the sample or reference. Furthermore, the systems can be capable of detecting the substance along various locations and depths within the sample by mapping a detector pixel and a microoptics to the location and depth in the sample.

A method of spectroscopy, comprises: transmitting output radiation to a sample; collecting from the sample input radiation being indicative of interaction between the output radiation and the sample; modulating at least one of the output radiation and the input radiation, wherein at least one of the output radiation and the modulation is characterized by a scanned parameter; combining the input radiation, following the modulation, with a reference signal to provide a combined signal; processing the combined signal to construct a vector describing a dependence of a radiation property of the input radiation on the parameter; and at least partially identifying the sample or a change in comprises sample based on at least the vector.

Detector data representative of an intensity of light that impinges on a detector after being emitted from a light source and passing through a gas over a path length can be analyzed using a first analysis method to obtain a first calculation of an analyte concentration in the volume of gas and a second analysis method to obtain a second calculation of the analyte concentration. The second calculation can be promoted as the analyte concentration upon determining that the analyte concentration is out of a first target range for the first analysis method.

Detector data representative of an intensity of light that impinges on a detector after being emitted from a light source and passing through a gas over a path length can be analyzed using a first analysis method to obtain a first calculation of an analyte concentration in the volume of gas and a second analysis method to obtain a second calculation of the analyte concentration. The second calculation can be promoted as the analyte concentration upon determining that the analyte concentration is out of a first target range for the first analysis method.