A cavity enhanced absorption spectroscopy (CEAS) system is provided that utilizes collimators the incorporate gradient index (GRIN) lenses in lieu of conventional spherical or aspheric refractive lenses. The use of smaller diameter GRIN lenses facilitates a reduced initial beam size entering the sample cavity, which reduces self-interference noise and increases a signal to noise ratio of the measurements. Further, a reduced size and mass of the GRIN lens can reduce a size of the mounting hardware utilized to mount the optical components, which enables more laser beams to be coupled to a single gas cell compared to a similar gas cell integrated with conventional refractive collimators. A larger number of lasers enables more gas peaks to be measured substantially simultaneously using the CEAS system.

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.

A spectroscopy system is disclosed, and includes a resonant cavity, a first conduit configured to couple at a first end thereof to a gas source, and at a second end thereof to a first end of a sorbent tube containing a sample for analysis, and a second conduit configured to couple at a first end thereof to a second end of the sorbent tube, and at a second end thereof to the resonant cavity.

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.

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.

Methods and systems for analyzing a sample and generating a predictive model using cavity ring-down spectroscopy are disclosed. At least part of a sample is loaded in a ring-down cavity. For each of a set of wavelengths, a laser beam is generated and directed into the ring-down cavity. The laser beam entering the ring-down cavity is extinguished. Light intensity decay data for light exiting the ring-down cavity is registered via a light intensity sensor system. A probability is determined from the light intensity decay data for the set of wavelengths that a subject from which the sample was received has a physiological condition or a degree of the physiological condition at least indirectly using a dataset of light intensity decay data for previously analyzed samples for which the presence or the absence of the physiological condition or the degree of the physiological condition have been identified.

A laser system with optical feedback, includes an optical-feedback-sensitive laser which emits, via an output optical fibre, a continuous, frequency-adjustable, propagating, source optical wave, known as the source wave; a resonant optical cavity coupled by means of optical feedback to the laser and configured to generate an intra-cavity wave, one fraction of which returns to the laser in the form of a counter-propagating optical wave; an electro-optic fibre modulator placed on the optical path between the laser and the resonant optical cavity, the electro-optic modulator being configured to generate a phase-shifted source wave by phase-shifting the source wave and, by phase-shifting the counter-propagating optical wave, to generate a phase-shifted counter-propagating wave, known as the feedback wave, which reaches the laser; a phase-control device for generating a control signal for the electro-optic modulator from an error signal representative of the relative phase between the source wave and the feedback wave, such as to cancel the relative phase between the source wave and the feedback wave.

Spectroscopic apparatus and methods incorporating a gas sensor configured to detect low concentration gases, including gases that are hazardous volatiles are provided. Low concentration gases can comprise gases where detection of concentrations on the order of parts-per-million (ppm), and in many embodiments part-per-billion (ppb) is required. The gas may be a species, such as, for example hydrogen sulfide (H.sub.2S) that may be produced in drilling and/or volcanic eruptions. The spectroscopic apparatus and methods are configured to operate in particular atmospheres where gas detection can be challenging, such as in ambient air and/or in space where various contaminants may be present. The spectroscopic apparatus and methods may incorporate a long path length detector, such as, for example, a cavity-enhanced absorption spectrometer. The methods and apparatus further incorporate a wavelength modulation technique to improve the signal-to-noise ratio.

Methods, devices, and systems for elongating a beam path of a light beam, in particular of a laser beam, are provided. An example method includes coupling the light beam into an interspace between a plurality of first reflective surfaces and a plurality of second reflective surfaces facing the first reflective surfaces, multiply reflecting the light beam between the first reflective surfaces and the second reflective surfaces to elongate the beam path of the light beam, and coupling out the light beam from the interspace. The light beam undergoes the steps of coupling in, repeated reflecting and coupling out at least a first time with a first pass and a second time with a second pass, and the light beam traverses a different beam path in the interspace during the first pass in comparison with during the second pass.

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.