Abstract: A gaseous target analyte present as a minor constituent in an admixture with at least one other gaseous species can be detected using a cavity enhanced optical spectrometer by a process comprising the steps of: i) identifying a plurality of strong spectral absorption peaks of the target analyte which are present within the scanning range of the spectrometer, ii) determining for the identified peaks the pressure region above which the peak width increases substantially with increasing pressure and below which the peak width is substantially independent of pressure, iii) determining which of the peaks identified in step i) are, within the pressure region determined in step ii), free from spectral interference by any of the other components of the admixture. iv) measuring the spectrum of the admixture at the pressure region identified in step ii).

Abstract: Improved cavity ring down spectroscopy is provided by binning decay time vs. wavelength data into wavelength bins defined by discontinuities in a wavelength monitor signal. Average decay times and average wavelengths are computed for each bin. The optical loss of a target analyte at the average wavelengths is determined from the corresponding average decay times.

Abstract: A cavity enhanced optical detector comprising: i) a source of continuous wave laser light; ii) a high finesse resonant cavity comprising at least three spaced apart, high-reflectivity mirrors positioned to receive light from the laser light source; iii) at least one photo-detector for measuring the extinction coefficient of an analyte that is positioned in the resonant cavity; and iv) one or more additional photo-detectors for measuring the intensity of fluorescence emission and/or Raman scattering from the analyte.

Abstract: A periodically poled second harmonic generating crystal having a long axis, said crystal comprising Magnesium Oxide doped Congruent Lithium Niobate, Magnesium Oxide doped Stoichiometric Lithium Niobate, Stoichiometric Lithium Tantalate or Potassium Titanyl Phosphate wherein the poling planes of said periodically poled crystal are canted relative to said axis and a doubled, external cavity laser utilizing said crystal, comprising an external cavity pump laser section and an extra-cavity frequency doubling section.

Abstract: An apparatus for cavity enhanced optical detection having an improved flow cell is provided. Sensitivity of the cavity resonance condition to changes in refractive index of an analyte flowing through the flow cell is reduced. More specifically, the round trip optical path defined by the resonant cavity intersects a curved cavity input mirror at a point. This point has a location on the input mirror that is substantially independent of the refractive index of the analyte. In this manner, changes in sample refractive index do not lead to misalignment of the resonant optical cavity.

Abstract: A cavity ring-down spectrometer includes: a) multiple detectors for monitoring the intensity of the radiation emitted from the cavity and the wavelength of the radiation injected into the cavity; b) controllers which turn off the radiation into the cavity and precisely adjust the temperature of, and current to, the laser gain medium; and c) means for adjusting the beam path length of the optical cavit to bring the cavity into resonance with the injected radiation. Additionally, disclosed is a method for using the spectrometer to detect a target analyte.

Abstract: A process for measuring the absorption spectrum of a target analyte using a cavity ring down spectrometer, comprising the steps of: i) tuning the spectrometer laser so that the light transmitted from the laser into the spectrometer optical cavity is varied over a wavelength interval which encompasses both the absorption wavelength of a spectral feature of the target analyte and a plurality of the free spectral ranges of the optical cavity; ii) triggering a plurality of ringdown events; iii) for each ringdown event, recording the decay time constant and the trigger time at which the light into the cavity is shut off; iv) organizing the decay time constants, light wavelengths and trigger times as a function of trigger time; v) ordering said light wavelengths by increasing value and placing groups of wavelengths into individual bins; vi) computing the average wavelength of each bin group; vii) grouping the decay time constants and trigger times into bins that parallel said wavelength bins, with the decay time co

Abstract: A novel control system for a simple and compact all-solid-state laser generating 300 nm to 600 nm nm light with continuously variable output power in the range from 1 mW to at least 120 mW. Single frequency radiation from an external cavity semiconductor laser is frequency doubled in a periodically poled MgO:LiNbO3 waveguide. The laser maintains a high quality TEM00 circular beam with M2<1.1 and very low noise of less than 0.06% over the entire range of output power. Less than 0.1% peak-to-peak output power variation is measured during prolonged operation. In one example, no degradation of the conversion efficiency is observed for operation at an output power of 70 mW and the laser has a small footprint of only 5×8 cm.

Abstract: A novel control system for a simple and compact all-solid-state laser generating 300 nm to 600 nm nm light with continuously variable output power in the range from 1 mW to at least 120 mW. Single frequency radiation from an external cavity semiconductor laser is frequency doubled in, for example, a periodically poled MgO:LiNbO3 ridge waveguide. Our laser maintains a high quality TEM00 circular beam with M2<1.1 and a very low. noise of less than 0.06% over its range of output power. Less than 0.1% peak-to-peak output power variation is seen even during prolonged operation. In one example, no degradation of the conversion efficiency is observed for operation at an output power of 70 mW, and the laser has a small footprint of 5 cm.×8 cm.

Abstract: A method for analyzing gas concentration using doubly resonant photoacoustic spectroscopy, and a doubly resonant photaoacoustic gas detector comprising: i) a continuous wave light beam whose wavelength coincides with an absorption wavelength of a gaseous analyte; ii) a closed path optical cavity having at least two reflective surfaces; iii) an acoustic resonator chamber contained within said optical cavity, and comprising an acoustic sensor for detecting sound waves generated by a gaseous analyte present within said chamber, the light beam passing sequentially into, through and out of said chamber, and being repeatedly reflected back and forth through said chamber, and being modulated at a frequency which is equal to or equal to one-half of an acoustic resonance frequency of said acoustic resonator chamber.

Abstract: Stable single mode operation of an external cavity semiconductor laser is obtained by a laser control method that monitors at least one optical beam which is generated by reflection from a wavelength selective element within the laser cavity. The method of the present invention provides stable single mode operation and significantly decreases the mode hop rate, because the signal obtained by reflection from a wavelength selective element within the laser cavity provides a clear indication of an impending mode hop.

Abstract: A gaseous target analyte present as a minor constituent in an admixture with at least one other gaseous species can be detected using a cavity enhanced optical spectrometer by a process comprising the steps of: i) identifying a plurality of strong spectral absorption peaks of the target analyte which are present within the scanning range of the spectrometer, ii) determining for the identified peaks the pressure region above which the peak width increases substantially with increasing pressure and below which the peak width is substantially independent of pressure, iii) determining which of the peaks identified in step i) are, within the pressure region determined in step ii), free from spectral interference by any of the other components of the admixture. iv) measuring the spectrum of the admixture at the pressure region identified in step ii).

Abstract: Target analytes present in low concentration as components in a gaseous admixture can be detected using a cavity enhanced optical spectrometer by a process comprising: i) identifying from the spectrum of the pure target analyte a series of absorption peaks free from spectral interference by peaks of any additional gaseous species which are present, the first member of the series being the strongest spectral absorption peak of said target analyte ii) identifying one or more successive peaks of the series which have an absorption that is weaker than the immediately previously identified peak of the series, iii) performing a spectral scan at the wavelengths of the peaks identified in steps i) and ii), and iv) calculating the concentration of the target analyte from the spectral scan of the admixture performed at the wavelength determined in step iii).

Abstract: A doubled, external cavity laser comprises an external cavity pump laser section and an extra-cavity frequency doubling section. The pump laser section comprises an edge-emitting, semiconductor chip having: i) an anti-reflection coating on the chip facet facing the cavity ii) a low reflectivity coating on the output facet of the cavity, iii) a wavelength selective element on the anti-reflection side of the chip for producing a single-mode output beam, iv) at least one lens on the output side of the chip which operates to collimate the chip output beam and direct it to the frequency doubling section.

Abstract: A tunable laser and laser tuning method based on the use of a tunable etalon in reflection as a mirror within a laser cavity. The laser emission wavelength is not necessarily at a wavelength of peak etalon reflectivity. A preferred embodiment makes use of a microelectromechanical etalon to tune an external cavity semiconductor laser.

Abstract: A tunable laser and laser tuning method, based on the interaction of a spectrally dependent beam distortion and a spatial filter within a laser cavity. One embodiment of this laser is an external cavity semiconductor laser in which broad tunability is obtained by the insertion of an acousto-optic tunable filter (AOTF) into the laser cavity such that the intra-cavity laser beam passes through the AOTF in zeroth order.

Abstract: A tunable laser and laser tuning method based on the use of a tunable etalon in reflection as a mirror within a laser cavity and forming an end reflective surface thereof. The laser emission wavelength is not necessarily at a wavelength of peak etalon reflectivity. A preferred embodiment makes use of a microelectromechanical etalon to tune an external cavity semiconductor.

Abstract: A system and method for controlling the light source of a cavity ring-down spectrometer (CRDS). The system comprises a resonant optical cavity having at least two high reflectivity mirrors; a source for providing a continuous wave optical signal into the optical cavity, the source comprising an electrically pumped semiconductor gain medium; and a SOA interposed between the optical signal source and the optical cavity. The SOA receives the optical signal and transmits it to the resonant optical cavity.

Abstract: A laser tuning mechanism which embodies “spectrally dependent spatial filtering” (SDSF) and contemplates two key elements of the tuning mechanism. The first element of the SDSF tuning mechanism is a spectrally dependent beam distortion (i.e. alteration of the amplitude and/or phase profile of the beam) provided by an SDSF tuning element in a laser cavity. The second element of the SDSF tuning mechanism is an intracavity spatial filter which makes the round trip cavity loss a sensitive function of both beam distortion and cavity alignment. Such a laser can be aligned so that a specific beam distortion, which is provided by the SDSF tuning element at a tunable wavelength, is required to obtain minimum round trip cavity loss, thereby providing tunable laser emission. A preferred embodiment of the SDSF tuning mechanism is an external cavity semiconductor laser having a zeroth order acousto-optic tuning element.

Abstract: A laser tuning mechanism which embodies “spectrally dependent spatial filtering” (SDSF) and contemplates two key elements of the tuning mechanism. The first element of the SDSF tuning mechanism is a spectrally dependent beam distortion (i.e. alteration of the amplitude and/or phase profile of the beam) provided by an SDSF tuning element in a laser cavity. The second element of the SDSF tuning mechanism is an intracavity spatial filter which makes the round trip cavity loss a sensitive function of both beam distortion and cavity alignment. Such a laser can be aligned so that a specific beam distortion, which is provided by the SDSF tuning element at a tunable wavelength, is required to obtain minimum round trip cavity loss, thereby providing tunable laser emission. A preferred embodiment of the SDSF tuning mechanism is an external cavity semiconductor laser having a zeroth order acousto-optic tuning element.