102 results about "Cavity ring-down spectroscopy" patented technology

The present invention relates to optical heterodyne detection cavity ringdown spectroscopy. In one aspect the invention relates to an optical system (1) comprising a ring-down cavity cell (3) defining a resonant optical cavity, means for directing coherent light selected from the group consisting of continuous or quasi-continuous light into said optical cavity (8, 9, 10, 11, and 12), means for altering the resonant optical cavity so as to generate a frequency shift of the coherent light in the optical cavity (6, 7), means for coupling said coherent light into the optical cavity and means for decoupling the frequency shifted coherent light out of said optical cavity (5, 6, 7), means for optically combining (10, 11, 12) said decoupled frequency shifted coherent light with another portion of coherent light not in optical communication with the optical cavity and means for optical heterodyne detection (13) of the intensity of said combined light. A method for optical detection is also described as well as methods and apparatus for detecting a parameter of a sample.

The invention discloses an infrared cavity ring-down spectroscopy trace gas detection method based on quantum cascade laser; comprising the following steps: using a tunable quantum cascade laser as alight source, and selecting measuring waveband and wavelength scan step length aiming at spectrum line characteristic of the gas to be detected; respectively measuring the cavity ring-down time of each wavelength in the cavity with absorption or without absorption by cavity ring-down technique, and calculating the gas absorption coefficient of corresponding wavelength so as to obtain a relation curve that is an absorption spectrogram of the measured gas absorption coefficient and toned laser wavelength. The spectrogram is contrasted with spectrum line characteristic of corresponding gas in HITRAN database, thereby being capable of analyzing and determining weather the measured gas contains the predetermined gas component; the absolute concentration of the gas to be measured can be calculated and obtained and the absolute concentration of the gas to be measured can be measured through scaling measurement by using absorption peak wavelength of the absorption spectrum as the best detection wavelength and the relation among the gas absorption coefficient of the wavelength, the absorption cross section and concentration. The method has high measuring sensitivity and high property of resisting interference so that the fast and exact on-line analysis and detection of multiple trace gases are easily realized.

The invention discloses a method for simultaneously measuring multicomponent gas based on cavity ring-down spectroscopy. A broadly tunable light source outputs a light beam, and the light beam enters a gas cell with two ends provided with plano-concave high-reflectance endoscopes. The gas cell is filled with a multicomponent gas mixture having absorption spectrum within laser tuning range. Output wavelengths of the laser undergo tuning, ring-down signals are detected under different wavelengths, ring-down time under different wavelengths is obtained through single exponential fitting, and a relation curve of absorption coefficient and wavelength is further obtained. A spectral line of the measured gas mixture and a standard absorption line of each single gas in the database undergo fitting treatment, and concentrations of different gases in the gas mixture can be simultaneously calculated. By the utilization of the broadly tunable laser light source, a gas absorption spectrum with richer contents can be obtained, and multiple gases can be measured at real time. Macromolecules with wide spectrum absorption undergo concentration detection, and the detection result is not influenced by light source fluctuation.

This invention relates to a compact cavity ring down spectrometer for detection and measurement of trace species in a sample gas using a tunable solid-state continuous-wave mid-infrared PPLN OPO laser or a tunable low-power solid-state continuous wave near-infrared diode laser with an algorithm for reducing the periodic noise in the voltage decay signal which subjects the data to cluster analysis or by averaging of the interquartile range of the data.

A time-resolved spectroscopy system employing a time-division multiplexing optical device with no dispersive optical elements to perform lifetime and concentration measurements in multi-species samples, is disclosed. Some examples include fluorescence and cavity ring-down spectroscopy. The system is unique in its compactness and simplicity of operation. In one embodiment, the system makes use of only one photo-detector and an efficient linear regression algorithm. The system offers a measurement time for multiple species measurements of less than 1 s. The system can also be used to perform fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy. Four methods to de-convolve a multi-component, exponentially decaying optical signal such as obtained with the system disclosed here, are presented. These methods may be applied to the measurement of fluorescence decay lifetimes and cavity ring-down times, the latter used extensively for the measurement of gas and trace-gas concentrations in complex mixtures, via absorption spectroscopy.

The present invention provides a gas sensor and a method for detecting the hydrogen fluoride gas concentration change by using the gas sensor. The gas sensor comprises a first laser device, a second laser device, a polarizer, an electro-optical modulator, a first isolator, a first EDFA, a second isolator, a first wave filter, an F-P cavity, a circulator, a first coupler, a second coupler, a second EDFA, a second wave filter, a third coupler and a detector, wherein the first coupler, the second coupler, the circulator, the F-P cavity, the second EDFA, the second wave filter and the third coupler form an annular cavity, the hollow optical fiber core of the F-P cavity is filled with hydrogen fluoride gas to be detected, and the hydrogen fluoride gas concentration change can be obtained by measuring the ring-down time change of the pulse signal light. According to the present invention, the hollow optical fiber photo-thermal technology, the F-P cavity interference technology and the annular cavity ring-down spectroscopy technology are combined so as to improve the detection sensitivity of the measured gas and reduce the influence of the light source fluctuation on the measurement result.

The invention provides a double-channel light cavity ring-down atmospheric aerosol extinction instrument and an extinction factor measuring method. According to the extinction instrument, utilizes a double-channel light cavity ring-down spectrum technology is applied to carry out in-situ real-time measurement on an extinction factor of atmospheric aerosol. The instrument comprises a light path system, a circuit system and a gas path system, wherein the light path system is internally provided with a first light cavity and a second light cavity, and the first light cavity and the second light cavity are utilized as double channels; and the gas path system respectively provides atmospheric gas and background atmospheric gas containing the aerosol for the first light cavity and the second light cavity, the circuit system can eliminate the transformation of the extinction factor of the aerosol caused by gas change in real time, and the extinction factor value of the atmospheric aerosol is accurately measured in a real time.

This invention relates to a compact cavity ring down spectrometer for detection and measurement of trace species in a sample gas using a tunable solid-state continuous-wave mid-infrared PPLN OPO laser or a tunable low-power solid-state continuous wave near-infrared diode laser with an algorithm for reducing the periodic noise in the voltage decay signal which subjects the data to cluster analysis or by averaging of the interquartile range of the data.

An apparatus for detection and measurement of trace species in a gas or liquid sample. A ring down cell formed from a fiber optic ring is exposed to the sample gas or liquid. A coherent source emits radiation into the fiber optic ring, which in turn is received at an output thereof. The fiber optic ring has a portion thereof, between the input and output, exposed to the sample gas or sample liquid. A processor is coupled to the receiver and determines the level of trace species in the gas or liquid sample based on the rate of decay of the radiation within the fiber optic ring.

An apparatus and method for analyzing an impurity on a gas is provided. The apparatus includes a first cell containing a first gas with the impurity and a second cell containing a second gas absent the impurity. A first light beam is coupled into the first cell and a second light beam is coupled into the second cell. A first detector is coupled to an output of the first cell and generates a first signal based on a decay rate of the first light beam within the first cell. A second detector is coupled to an output of the second cell and generates a second signal based on a second decay rate of the second light beam within the second cell. The concentration of the impurity is determined based on a difference between the first decay rate and the second decay rate.

The invention relates to a laser cavity ring-down spectrometer for simultaneous detection of aerosol extinction and scattering coefficients. The spectrometer comprises a gas path system, a light cavity, a first photomultiplier and a second photomultiplier, wherein the first photomultiplier is used for detecting transmission light of the light cavity; the second photomultiplier is used for integral measurement of scattered light and stretches into the light cavity from the side surface of the light cavity; the gas path system is used for providing sample gas or background gas for the light cavity periodically. Because the gas path system feeds the background gas and the sample gas with aerosol into the light cavity periodically, the spectrometer disclosed by the invention can detect the transmission light and the scattered light of the light cavity respectively through the first photomultiplier and the second photomultiplier, and can calculate ring-down time of the background gas and ring-down time of the sample gas through fitting respectively, thus calculating extinction coefficient of the aerosol; simultaneously, the spectrometer can calculate ratio of transmission light intensity to scattered light intensity to obtain scattering coefficient of the aerosol, and the spectrometer is low in detection error and high in precision. The ring-down spectrometer disclosed by the invention is applicable to online analysis and detection of optical properties of atmosphere aerosol.

The invention provides an optical fiber current sensor based on the ring cavity ring-down spectroscopy technology, and belongs to the field of optical fiber sensing and magnetic fluid materials. The sensor comprises a tunable laser, an electro-optical modulator, a waveform generator, an optical isolator No.1, a 2*2 coupler No.1, a current sensing unit, an optical isolator No.2, a time-delay single mode fiber, a 2*2 coupler No.2, a high-speed photoelectric detector and a spectrograph, wherein the 2*2 coupler No.1, the current sensing unit, the optical isolator No.2, the time-delay single mode fiber and the 2*2 coupler No.2 are combined to form a ring cavity. The sensor has the advantages of being practical, reliable, ingenious in design, high in measurement precision and convenient for tuning.

The invention discloses a system for detecting water-vapor content in a high-purity gas based on a cavity ring down spectroscopy technology. The system comprises a DFB laser control power source, a DFB laser, an optical collimator, an optical isolator, an acoustic optical modulator, a reflector, a matching lens, an optical resonator, piezoelectric ceramics, a piezoelectric ceramics control power source, a focusing lens, a detector, a trigger, a data acquisition card, and a computer. The laser emitted by the DFB laser successively passes through the optical collimator, the optical isolator, the acoustic optical modulator, the reflector, the matching lens, the optical resonator, the piezoelectric ceramics, and the focusing lens, and arrives to the detector. The piezoelectric ceramics control power source is connected with the piezoelectric ceramics. The detector is connected with the trigger and the data acquisition card. The trigger is connected with the acoustic optical modulator. The collected data of the data acquisition card is transmitted to the computer. Based on the system, the detection precision of the water-vapor content in the high-purity gas is about 100 pptv. In addition, the system does not need to calibrate instruments frequently, and the requirement for the environment humidity is high.

A highly sensitive trace gas sensor based on Cavity Ring-down Spectroscopy (CRDS) makes use of a high power, multi-mode Fabry-Perot (FP) semiconductor laser with a broad wavelength range to excite a large number of cavity modes and multiple molecular transitions, thereby reducing the detector's susceptibility to vibration and making it well suited for field deployment. The laser beam is aligned on-axis to the cavity, improving the signal-noise-ratio while maintaining its vibration insensitivity. The use of a FP semiconductor laser has the added advantages of being inexpensive, compact and insensitive to vibration. The technique is demonstrated using a laser with an output power of at least 200 mW, preferably over 1.0 Watt, (λ=400 nm) to measure low concentrations of Nitrogen Dioxide (NO₂) in zero air. For single-shot detection, 530 ppt sensitivity is demonstrated with a measurement time of 60 μs which allows for sensitive measurements with high temporal resolution.

The invention discloses a device for measuring the water vapor content in a gas by using an optical cavity ring-down spectroscopy to self-calibrate a measurement unit. The device comprises a laser, an optical ring-down cavity, an photoelectric detector and a data collector, wherein the laser is used for outputting laser to the optical ring-down cavity; the optical ring-down cavity is an optical resonant cavity and is used for receiving the gas to be measured and allows the incoming laser to reflect back and forth repeatedly and outputs laser that gradually rings down; the photoelectric detector is receiving the laser emitted by the optical ring-down cavity, and generates an electrical signal according to the light intensity of the emitted laser, the ring-down time can be calculated by using the electrical signal, and the ring-down time can be used for calculating the water vapor content of the gas to be measured; and the trigger data collector is used for receiving and recording the electrical signal output by the photoelectric detector. According to the invention, the self-calibration of the measurement unit is realized based on the optical cavity ring-down spectroscopy by using the fixed optical cavity length, and the requirement of accurate quantitative measurement is achieved.

Combining the approaches of cavity ring down spectroscopy with surface plasmon resonance spectroscopy allows creation of an ultra-high sensitivity apparatus to detect extremely low concentrations of chemicals and biomolecules.

An apparatus and method for analyzing an impurity in a liquid. The apparatus comprises a cell coupled to a light source and a detector. The cell includes a first mirror at a first end of the cell to receive and pass the light into the cell along a longitudinal axis of the cell, and a second mirror at a second end of the cell to at least partially reflect the light. A liquid supply device projects a stream of the liquid between the first mirror and the second mirror and across the longitudinal axis of the cell. The detector is coupled to the second end of the cell and determines a decay rate of the light within the cell based on the light passing through the liquid.

An apparatus and method for controlling a light source used in Cavity Ring-Down Spectroscopy. The apparatus comprises a controller that generates a control signal to activate and deactivate the light source based on a comparison of an energy signal from a resonant cavity and a threshold. The light source is activated for a time period based on the stabilization time of the light source and the time necessary to provide sufficient energy to the resonant cavity. Thereafter the controller deactivates the light source for a predetermined time period by interrupting its current source so that the light energy in the cavity rings down and so that the presence of analyte can be measured. The light energy from the light source is directly coupled to the resonant cavity from the light source.

The invention discloses a cavity ring down spectroscopy (CRDS) technique based blood component recognizing and analyzing instrument. The instrument comprises an optical platform, a blood volatile gas collecting device, an analog-digital converter and a computer, wherein the optical platform comprises a laser light source module, an optical oscillating cavity, a thin film pressure sensor and a photomultiplier. According to the instrument disclosed by the invention, the concentration of volatile organic compounds (VOCs) in blood volatile gas is detected by utilizing low-cost ultra-sensitivity and high-accuracy CRDS technique and a background deduction method, so that different blood components can be detected.

The invention provides an atmosphere visibility measurement device based on an optical cavity ring down spectroscopy technology and relates to a meteorological observation device. The atmosphere visibility measurement device comprises a saddle-shaped shell; a pair of high-reflectivity cavity mirrors are located at the two sides of a concave opening of the shell to form a ring down cavity; after laser transmitted by a laser transmitter penetrates through a polaroid, a 1/4 wave plate and a coupling lens in sequence and then is mitted into a first high-reflectivity cavity mirror, one path is reflected by the first high-reflectivity cavity mirror and is emitted into the polaroid through the 1/4 wave plate to be reflected and output; and the other path is vibrated in the ring down cavity, penetrates through the second high-reflectivity cavity mirror to be transmitted to a photomultiplier, and then is transmitted to a computer by a data acquisition card. By virtue of the atmosphere visibility measurement device, the technical problems that a measurement error is caused by the fact that the deviation is caused between the sampling of a sample to be detected for measuring the atmosphere visibility and the actual measurement in the prior art are solved. The atmosphere visibility measurement device has the beneficial effects that the open type ring down cavity can be in direct contact with atmosphere, and atmosphere extinction coefficient changes caused by gas molecules, aerosol and rainwater can be comprehensively measured, so that the accurate measurement of the atmosphere visibility is realized.