Abstract: Methods and apparatus for analyzing optical measurements to determine whether a liquid includes dissolved oxygen, to determine a predicted concentration of the dissolved oxygen in the liquid, and/or to determine additional or alternative feature(s) related to dissolved oxygen in the liquid. An optical source can be controlled to emit optical radiation into a container that contains the liquid. The optical source can be located outside of the container, and the optical radiation includes (e.g., is restricted to) radiation that conforms to a dissolved oxygen absorption band. The optical radiation can be pulsed or can be periodically intensity modulated. A photodetector, located outside of the container but in optical communication with the interior of the container, can generate the optical measurements used in the analysis.

Abstract: Implementations are described herein for isolating mirrors and/or other potentially-vulnerable components of multi-pass optical systems from samples being analyzed, while mitigating interference and/or reduction in optical power. In one implementation, an apparatus may include: an optical cell with one or more passages, the one or more passages provided for introducing a sample into an interior of the optical cell for analysis and for removing the sample from the interior; a first mirror with a first reflective surface that faces the interior of the optical cell; one or more additional mirrors with one or more corresponding additional reflective surfaces that face the first reflective surface of the first mirror; and a wedge-shaped optical element positioned between the first mirror and the interior of the optical cell.

Abstract: Methods and apparatus for analyzing optical measurements to determine whether a liquid includes dissolved oxygen, to determine a predicted concentration of the dissolved oxygen in the liquid, and/or to determine additional or alternative feature(s) related to dissolved oxygen in the liquid. An optical source can be controlled to emit optical radiation into a container that contains the liquid. The optical source can be located outside of the container, and the optical radiation includes (e.g., is restricted to) radiation that conforms to a dissolved oxygen absorption band. The optical radiation can be pulsed or can be periodically intensity modulated. A photodetector, located outside of the container but in optical communication with the interior of the container, can generate the optical measurements used in the analysis.

Abstract: Implementations are described herein for isolating mirrors and/or other potentially-vulnerable components of multi-pass optical systems from samples being analyzed, while mitigating interference and/or reduction in optical power. In one implementation, an apparatus may include: an optical cell with one or more passages, the one or more passages provided for introducing a sample into an interior of the optical cell for analysis and for removing the sample from the interior; a first mirror with a first reflective surface that faces the interior of the optical cell; one or more additional mirrors with one or more corresponding additional reflective surfaces that face the first reflective surface of the first mirror; and a wedge-shaped optical element positioned between the first mirror and the interior of the optical cell.

Abstract: Aspects of the disclosure include suppression of optical interference fringes in optical spectra via a modification to the refractive index of media that forms or is contained in one or more components of equipment utilized for optical spectroscopy. Such a modification can yield changes in the optical path of light propagating through at least one of the media, with the ensuing changes in the spectral structure of interference between light propagating through different optical paths. In certain embodiments, the refractive index of the media that forms or is contained in one or more components can be modified via application of a time-dependent stimulus to at least one of the one or more components. The applied stimulus can include pressure, mechanical strain or stress, temperature, a combination thereof, or the like.

Abstract: Aspects of the disclosure include suppression of optical interference fringes in optical spectra via a modification to the refractive index of media that forms or is contained in one or more components of equipment utilized for optical spectroscopy. Such a modification can yield changes in the optical path of light propagating through at least one of the media, with the ensuing changes in the spectral structure of interference between light propagating through different optical paths. In certain embodiments, the refractive index of the media that forms or is contained in one or more components can be modified via application of a time-dependent stimulus to at least one of the one or more components. The applied stimulus can include pressure, mechanical strain or stress, temperature, a combination thereof, or the like.

Abstract: Aspects of the disclosure include pressure modulation of a fluid contained in a compartment and/or controlled release of an amount of such a fluid. In one aspect, an apparatus having a magnetic locking mechanism can passively control the cyclical injection and release of fluid from the apparatus, whereby pressure of the fluid in the compartment can switch between first and second pressures.

Abstract: A device comprising an acoustic detector, one or more thermal sensing elements coupled to the acoustic detector, and a light source. A method comprising directing a beam of light at a wavelength at or near one or more thermal sensing elements, wherein the thermal sensing elements are coupled to an acoustic detector, determining a resonance frequency of the acoustic detector, wherein the acoustic detector is coupled to one or more of the thermal sensing elements, and measuring the response of the acoustic detector to detect optical radiation absorption proximate to or at the surface of one or more thermal sensing elements.

Abstract: Novel methods and laser spectroscopic systems for accurately measuring the concentration of compounds are disclosed herein. The disclosed methods utilize a modulation cancellation technique resulting in a significantly increase in the sensitivity and accuracy of laser spectroscopic measurements. In general, the methods and systems utilize modulation phase-shifting and amplitude attenuation to cancel the signals detected from at least two modulated light beams. Thus, any signal detected will be directly proportional to the concentration measurement.

Abstract: A method for detecting a target fluid in a fluid sample comprising a first fluid and the target fluid using photoacoustic spectroscopy (PAS), comprises a) providing a light source configured to introduce an optical signal having at least one wavelength into the fluid sample; b) modulating the optical signal at a desired modulation frequency such that the optical signal generates an acoustic signal in the fluid sample; c) measuring the acoustic signal in a resonant acoustic detector; and d) using the phase of the acoustic signal to detect the presence of the target fluid.

Abstract: Novel methods and laser spectroscopic systems for accurately measuring the concentration of compounds are disclosed herein. The disclosed methods utilize a modulation cancellation technique resulting in a significantly increase in the sensitivity and accuracy of laser spectroscopic measurements. In general, the methods and systems utilize modulation phase-shifting and amplitude attenuation to cancel the signals detected from at least two modulated light beams. Thus, any signal detected will be directly proportional to the concentration measurement.

Abstract: A device comprising an acoustic detector, one or more thermal sensing elements coupled to the acoustic detector, and a light source. A method comprising directing a beam of light at a wavelength at or near one or more thermal sensing elements, wherein the thermal sensing elements are coupled to an acoustic detector, determining a resonance frequency of the acoustic detector, wherein the acoustic detector is coupled to one or more of the thermal sensing elements, and measuring the response of the acoustic detector to detect optical radiation absorption proximate to or at the surface of one or more thermal sensing elements.

Abstract: A method for detecting a target fluid in a fluid sample comprising a first fluid and the target fluid using photoacoustic spectroscopy (PAS), comprises a) providing a light source configured to introduce an optical signal having at least one wavelength into the fluid sample; b) modulating the optical signal at a desired modulation frequency such that the optical signal generates an acoustic signal in the fluid sample; c) measuring the acoustic signal in a resonant acoustic detector; and d) using the phase of the acoustic signal to detect the presence of the target fluid.

Abstract: The present invention provides methods and apparatus for flexible and reproducible control of quantum cascade laser frequency scans having short (nanosecond) pulse excitations. In accordance with a preferred embodiment of the invention, a method of digital frequency control for pulsed quantum cascade lasers includes digitally synthesizing a sub-threshold current, converting the sub-threshold current to analog form, and generating laser pulses. Preferably, the sub-threshold current is synchronized to the laser pulses.

Abstract: Methods and apparatus for detecting photoacoustic signals in fluid media are described. The present invention differs from conventional photoacoustic spectroscopy in that rather than accumulating the absorbed energy in the fluid of a sample cell, the absorbed energy is accumulated in an acoustic detector or sensitive element. In a preferred embodiment, the acoustic detector comprises piezoelectric crystal quartz. The quartz is preferably in the shape of a tuning fork.

Abstract: Methods and apparatus for detecting photoacoustic signals in fluid media are described. The present invention differs from conventional photoacoustic spectroscopy in that rather than accumulating the absorbed energy in the fluid of a sample cell, the absorbed energy is accumulated in an acoustic detector or sensitive element. In a preferred embodiment, the acoustic detector comprises piezoelectric crystal quartz. The quartz is preferably in the shape of a tuning fork.

Abstract: The present invention provides methods and apparatus for flexible and reproducible control ofquantum cascade laser frequency scans having short (nanosecond) pulse excitations. In accordance with a preferred embodiment of the invention, a method of digital frequency control for pulsed quantum cascade lasers includes digitally synthesizing a sub-threshold current, converting the sub-threshold current to analog form, and generating laser pulses. Preferably, the sub-threshold current is synchronized to the laser pulses.