Abstract:
Pulsed fluorescence imaging in a light deficient environment is disclosed. A system includes an emitter for emitting pulses of electromagnetic radiation and an image sensor comprising a pixel array for sensing reflected electromagnetic radiation. The system includes a controller configured to synchronize timing of the emitter and the image sensor. The system is such that at least a portion of the pulses of electromagnetic radiation emitted by the emitter comprises electromagnetic radiation having a wavelength from about 795 nm to about 815 nm.
Abstract:
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 (H2S) 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.
Abstract:
Frequency registration deviations occurring during a scan of a frequency or wavelength range by a spectroscopic analysis system can be corrected using passive and/or active approaches. A passive approach can include determining and applying mathematical conversions to a recorded field spectrum. An active approach can include modifying one or more operating parameters of the spectroscopic analysis system to reduce frequency registration deviation.
Abstract:
Devices, methods, and systems for cavity-enhanced spectroscopy are described herein. One system includes an optical frequency comb (OFC) coupled to a laser source, and a cavity coupled to the OFC comprising a number of mirrors, wherein at least one of the number of mirrors is coupled to a piezo-transducer configured to alter a position of the at least one of the number of mirrors.
Abstract:
A method and system for correcting the effect of intensity fluctuations of the transmitted light in an absorption spectroscopy system used for the detection or measurement of chemical species in a medium, whereby one or more modulation bursts are imposed onto a light beam that passes through the medium. This burst signal may be obtained by modulating the bias current of a tunable diode laser, and the modulation burst signal may be optimally at the second harmonic of the modulation frequency of a wavelength modulated beam to allow usage of the same signal path processing used for the spectroscopic detection of the measurand for a second harmonic detection system. The burst signal can be controlled using a smooth window function to minimise the effects of non-linear perturbations that are inherent in tunable diode laser wavelength modulation spectroscopy systems, of optical interference fringes (etalons) and of the residual light absorption by background chemical species or the measurand at the wavelength coinciding with the modulation burst.
Abstract:
A sample cell can be designed to minimize excess gas volume. Described features can be advantageous in reducing an amount of gas required to flow through the sample cell during spectroscopic measurements, and in reducing a time (e.g. a total volume of gas) required to flush the cell between sampling events. In some examples, contours of the inners surfaces of the sample cell that contact the contained gas can be shaped, dimensioned, etc. such that a maximum clearance distance is provided between the inner surfaces at one or more locations. Systems, methods, and articles, etc. are described.
Abstract:
A gas absorption spectroscopy system and method are provided. A sealed chamber is provided with a reference gas having a known moisture concentration. An illumination source is disposed in the sealed chamber and is configured to generate an illumination beam. A measurement cell is coupled to the sealed chamber and is configured for exposure to a gas sample such that illumination travelling through the measurement cell passes through the gas sample. A process window is disposed between the sealed chamber and the measurement cell. The process window is configured to receive the illumination beam from the illumination source and reflect a first portion of illumination while allowing a second portion of illumination to pass into the measurement cell. A reference detector is disposed to receive the first portion of illumination and provide a reference detector signal. A measurement detector is disposed to receive the second portion of illumination after the second portion of illumination has passed through the measurement cell and provide a measurement detector signal. A controller is coupled to the reference detector and the measurement detector and is configured to provide a compensated moisture output based on the reference detector signal and the measurement detector signal.
Abstract:
A broadband light source includes one or more laser diodes that are capable of generating a pump signal having a wavelength shorter than 2.5 microns, a pulse width of at least 100 picoseconds and a pump optical spectral width. The light source also includes one or more optical amplifiers that are coupled to the pump signal and are capable of amplifying the pump signal to a peak power of at least 500 W. The light source further includes a first fiber that is coupled to the one or more optical amplifiers. The first fiber including an anomalous group-velocity dispersion regime and a modulational instability mechanism that operates to modulate the pump signal. The light source also includes a nonlinear element that is coupled to the first fiber that is capable of broadening the pump optical spectral width to at least 100 nm through a nonlinear effect in the nonlinear element.
Abstract:
A broadband light source includes one or more laser diodes that are capable of generating a pump signal having a wavelength shorter than 2.5 microns, a pulse width of at least 100 picoseconds and a pump optical spectral width. The light source also includes one or more optical amplifiers that are coupled to the pump signal and are capable of amplifying the pump signal to a peak power of at least 500 W. The light source further includes a first fiber that is coupled to the one or more optical amplifiers. The first fiber including an anomalous group-velocity dispersion regime and a modulational instability mechanism that operates to modulate the pump signal. In one particular embodiment, the pump signal wavelength resides in the anomalous group-velocity dispersion regime of the first fiber and where different intensities in the pump signal can cause relative motion between different parts of the modulated pump signal produced through modulational instability in the first fiber. The light source also including a nonlinear element that is coupled to the first fiber that is capable of broadening the pump optical spectral width to at least 100 nm through a nonlinear effect in the nonlinear element.
Abstract:
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.