Abstract: A method and apparatus for the photo-acoustic identification and quantification of one or more analyte species present in a gaseous or liquid medium in low concentration utilizing a laser and a resonant optical cavity containing the medium and having within the cavity at least two partially transparent mirrors, one of which is a cavity coupling mirror and one of which is moveably mounted on an assembly responsive to an input signal.

Abstract: A method and apparatus for the photo-acoustic identification and quantification of one or more analyte species present in a gaseous or liquid medium in low concentration utilizing a laser and a resonant optical cavity containing the medium and having within the cavity at least two partially transparent mirrors, one of which is a cavity coupling mirror and one of which is moveably mounted on an assembly responsive to an input signal.

Abstract: A method and apparatus for the photo-acoustic identification and quantification of one or more analyte species present in a gaseous or liquid medium in low concentration utilizing a laser and a resonant optical cavity containing the medium and having within the cavity at least two partially transparent mirrors, one of which is a cavity coupling mirror and one of which is moveably mounted on an assembly responsive to an input signal.

Abstract: A method and apparatus for the photo-acoustic identification and quantification of one or more analyte species present in a gaseous or liquid medium in low concentration utilizing a laser and a resonant optical cavity containing the medium and having within the cavity at least two partially transparent mirrors, one of which is a cavity coupling mirror and one of which is moveably mounted on an assembly responsive to an input signal.

Abstract: Improved ease of mode matching to a passive optical cavity is provided by selecting a cavity design that has a predetermined deviation from a reference cavity design having high transverse mode degeneracy. This predetermined deviation tends to be small, so that the first overlap of high-order transverse modes with the lowest order transverse mode in frequency occurs at relatively high transverse mode numbers. Coupling to high-order transverse modes is thereby reduced, since high-order transverse modes having relatively high transverse mode numbers tend to be more difficult to couple to, and tend to have high loss. During assembly of such a cavity, it can be useful to apply a perturbation to the cavity to further optimize mode matching. For example, the length of an enclosed cavity can be adjusted by altering the number and/or length of spacers in the cavity housing.

Abstract: A thermal lens detection apparatus comprising: i) an optical cell for containing at least one target analyte present in a carrier liquid, ii) a probe beam having a pre-determined wavelength, iii) an excitation beam having a pre-determined wavelength shorter than that of the probe beam and a Rayleigh length approximately equal to the radius of said optical cell, the beam axis of said probe beam and the beam axis of said excitation beam being at an angle to each other but both the probe beam and excitation beam being focusable so that their beams overlap in the interior portion of the optical cell, iv) a signal photo-detector for receiving at least a portion of said probe beam signal after its passage through said optical cell, and iv) an optical cutoff filter which blocks the excitation beam from impinging on said signal photo-detector.

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 ease of mode matching to a passive optical cavity is provided by selecting a cavity design that has a predetermined deviation from a reference cavity design having high transverse mode degeneracy. This predetermined deviation tends to be small, so that the first overlap of high-order transverse modes with the lowest order transverse mode in frequency occurs at relatively high transverse mode numbers. Coupling to high-order transverse modes is thereby reduced, since high-order transverse modes having relatively high transverse mode numbers tend to be more difficult to couple to, and tend to have high loss. During assembly of such a cavity, it can be useful to apply a perturbation to the cavity to further optimize mode matching. For example, the length of an enclosed cavity can be adjusted by altering the number and/or length of spacers in the cavity housing.

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 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, 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 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 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 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 method and apparatus for adjusting the path of an optical beam and in particular, a method and apparatus for improving the coupling efficiency (power input) of free-space radiation into an optical waveguide using, as part of an optical train, a weak lens positioned along the path of the optical beam (the Z axis) and adapted to adjust the path of the beam. The weak lens is translatable along the Z axis and also along at least one axis perpendicular to the Z axis (the X or Y axes). In a preferred embodiment, the weak lens possesses all three positional degrees of freedom (i.e., it is adjustable along all of the X, Y, and Z axes). In certain preferred embodiments, the weak lens is also capable of one or even two orientational degrees of freedom (i.e., pitch and/or yaw).

Abstract: A method and apparatus for adjusting the path of an optical beam and in particular, a method and apparatus for improving the coupling efficiency (power input) of free-space radiation into an optical waveguide using, as part of an optical train, a weak lens positioned along the path of the optical beam (the Z axis) and adapted to adjust the path of the beam. The weak lens is translatable along the Z axis and also along at least one axis perpendicular to the Z axis (the X or Y axes). In a preferred embodiment, the weak lens possesses all three positional degrees of freedom (i.e., it is adjustable along all of the X, Y, and Z axes). In certain preferred embodiments, the weak lens is also capable of one or even two orientational degrees of freedom (i.e., pitch and/or yaw).

Abstract: A wavelength meter for measuring the wavelength of laser light includes a diffraction element for diffracting the light and a glass plate interferometer in light communication with the diffraction element for generating a sinusoidally-shaped interference fringe pattern. The interference fringe pattern is detected by a CCD array which sends a signal representative of the fringe pattern to a computer. The computer filters and analyzes the signal, and corrects the signal for temperature-induced changes in the optical path of the laser light beam. The computer compares the signal with a prestored signal representing a predetermined fringe pattern using a least-squares fit analysis, and from this analysis determines the wavelength of the laser light. An alignment assembly is provided for facilitating directing laser light through the aperture of the diffraction element.

Abstract: A wavelength meter for measuring the wavelength of laser light includes a diffraction element for diffracting the light and a glass plate interferometer in light communication with the diffraction element for generating a sinusoidally-shaped interference fringe pattern. The interference fringe pattern is detected by a CCD array which sends a signal representative of the fringe pattern to a computer. The computer filters and analyzes the signal, and corrects the signal for temperature-induced changes in the optical path of the laser light beam. The computer compares the signal with a prestored signal representing a predetermined fringe pattern using a least-squares fit analysis, and from this analysis determines the wavelength of the laser light.