A cavity ring-down spectroscopy system and a method of modulating a light beam therein are provided. The cavity ring-down spectroscopy system includes at least one laser that generates a light beam, a first optical modulator positioned to attenuate the light beam from the at least one laser, a second optical modulator positioned to attenuate the light beam from the first optical modulator, a ring-down cavity positioned to receive the light beam from the second optical modulator, and at least one light sensor to detect an intensity of light leaked from the ring-down cavity.

Improved optical absorption spectroscopy of species having broad spectral features is provided by choosing frequencies to cover the spectral feature(s) of interest, where the frequencies are slightly adjusted as needed to avoid narrow spectral features from interfering chemical species (i.e., clutter). The resulting clutter avoidance provides improved optical spectroscopy of species having broad spectral features.

There is provided a resonant cavity system. A first mirror is actuated at a first end of a resonant cavity to move in a direction between a first position relative to a second mirror at a second end of the resonant cavity, at which a cavity length between the first mirror and the second mirror is less than a resonance length for a laser beam, and a second position relative to the second mirror, at which the cavity length is greater than the resonance length. An event is triggered when the cavity length is proximal to the resonance length. The first mirror is continuously actuated to move in the direction between the first position and the second position during the event.

Apparatuses, methods, and systems for generating signatures based on sensing one or more gas concentration conditions are disclosed. One method includes sensing, by one or more sensors, levels of a gas over time for a plurality of gas concentration conditions, receiving, by a controller, the sensed levels of gas over time for the plurality of gas concentration conditions, and generating, by the controller, a plurality of signatures, wherein one or more signatures is generated for one or more gas concentration conditions based on the sensed levels of gas over time, and determining whether to take action or not to take action.

The present invention provides a self-aligned high finesse optical sensor cell for analyzing a gaseous sample using highly reflective optical minors with a light source and a detector coupled on either end of the cell, having flexibility and/or serviceability in self-aligning the highly reflective mirrors to the optical cell without any mechanical manipulations.

Apparatuses, methods, and systems for detecting a substance are disclosed. One system includes a light source, an optical cavity, a cavity detector, and a processor. The light source generates a beam of electro-magnetic radiation, wherein a wavelength of the beam of electro-magnetic radiation is tuned to operate at multiple wavelengths. The optical cavity receives the beam of electro-magnetic radiation, wherein the physical characteristics of the cavity define a plurality of allowed axial-plus-transverse electro-magnetic radiation modes, wherein only a subset of the allowed axial-plus-transverse electro-magnetic radiation modes are excited when the optical cavity receives the beam of electro-magnetic radiation. The cavity detector senses electro-magnetic radiation emanating from the optical cavity. The processor operates to receive information relating to the sensed electro-magnetic radiation, and detects the substance within the optical cavity based on amplitude and/or phase of the sensed electro-magnetic radiation emanating from the optical cavity.

There is provided a method of tuning a resonant cavity and a cavity ring-down spectroscopy system using the same. A first mirror is actuated at a first end of a resonant cavity to move in a direction between a first position relative to a second mirror at a second end of the resonant cavity, at which a cavity length between the first mirror and the second mirror is less than a resonance length for a laser beam, and a second position relative to the second mirror, at which the cavity length is greater than the resonance length. An event is triggered when the cavity length is proximal to the resonance length. The first mirror is continuously actuated in the direction between the first position and the second position during the event.

In some embodiments, data from a vehicle-borne gas leak detection survey are used to generate an aggregate leak indication search area (LISA) indicator for a plurality of leak indications (measurement peaks) characterizing a single leak or localized set of leaks. A clustering algorithm (e.g. Markov, DBScan) may be used to group a set of indications into a cluster characterizing the leak. Leak indications may be pre-filtered for quality control before assignment to a cluster according to a number of parameters including background gas level, inter-peak distance, peak shape, wind speed, wind direction and/or variability, vehicle speed and/or acceleration, and/or a lower detection threshold for leak flow rate.

A laser absorption spectrometry system for gas measurement is provided. The system includes an integrated cavity output spectroscopy (ICOS) assembly including a gas cell. The gas cell includes a cell body defining an optical cavity and an input mirror and an output mirror positioned in the optical cavity. The assembly further includes a tunable diode laser configured to emit laser light, a collimator positioned in an optical path between the tunable diode laser and the gas cell, and a detector arranged to measure laser light exiting the optical cavity. The collimator includes at least one of a reflective collimation mirror or a gradient index (GRN) lens.

The present invention is relative to a method of ring-down spectroscopy in saturated-absorption condition, for measuring a first concentration of a gas through a measurement of the spectrum of a molecular transition of said gas.