Abstract: T-sensor devices that include a main conduit that defines a diffusion space, at least a first and second supply conduit for conveying fluids into the main conduit, and at least one sensor having a sensing zone that extends into the diffusion space in a fixed location relative to the main conduit. The first and second supply conduits are separated by divider from which a diffusion interface extends into the diffusion space. In order to capture sensing information without employing moving the physical location of sensors or employing more sensors, devices according to the invention alter a location of a diffusion interface extending into the diffusion space from a diffusion start point on the divider relative to the sensing zone of the at least one sensor, without altering the fixed location of the sensor relative to the main conduit. Methods of sensing properties of fluids and analytes are also disclosed.

Abstract: An optical traveling-wave resonator that includes a magneto-optically active member through which an optical beam propagates on a non-planar optical propagation path circuit. The resonator further includes at least one mirror in the optical propagation path circuit and a magnetic field generator for applying a magnetic field to the magneto-optically active member such that resonant optical frequencies of normal modes corresponding to traveling waves in opposite directions are substantially different.

Abstract: In cavity ring-down spectroscopy (CRDS), scattering into the backward mode of a traveling wave ring-down cavity can degrade conventional CRDS performance. We have found that this performance degradation can be alleviated by measuring the backward mode signal emitted from the ring-down cavity, and using this signal to improve the processing for extracting ring-down times from the measured data. For example, fitting an exponential to the sum of the intensities of the forward and backward signals often provides substantially better results for the ring-down time than fitting an exponential to the forward signal alone. Other possibilities include extracting cavity eigenmode signals from the forward and backward signals and performing separate exponential fits to the eigenmode signals.

Abstract: An optical traveling-wave resonator that includes a magneto-optically active member through which an optical beam propagates on a non-planar optical propagation path circuit. The resonator further includes at least one mirror in the optical propagation path circuit and a magnetic field generator for applying a magnetic field to the magneto-optically active member such that resonant optical frequencies of normal modes corresponding to traveling waves in opposite directions are substantially different.

Abstract: In cavity ring-down spectroscopy (CRDS), scattering into the backward mode of a traveling wave ring-down cavity can degrade conventional CRDS performance. We have found that this performance degradation can be alleviated by measuring the backward mode signal emitted from the ring-down cavity, and using this signal to improve the processing for extracting ring-down times from the measured data. For example, fitting an exponential to the sum of the intensities of the forward and backward signals often provides substantially better results for the ring-down time than fitting an exponential to the forward signal alone. Other possibilities include extracting cavity eigenmode signals from the forward and backward signals and performing separate exponential fits to the eigenmode signals.

Abstract: Efficiency of fluid analysis can be improved by utilizing a rotary valve capable of sequentially coupling 3 or more buffer chambers to 3 or more tasks. Such a rotary valve can be provided using a rotor having connections that geometrically form parallel chords of a circle. During analysis, such a valve can provide for parallel processing of several tasks and buffers. For example, one buffer chamber can be connected to a cleaning/evacuation port, another buffer chamber can be connected to a sample input port, and a third buffer chamber can be connected to an analytical instrument. Stepping the valve through its various positions can simultaneously move each of the buffer chambers to the next step in an analysis process.

Abstract: Preparation methods for introducing liquid samples to gas analysis instruments include 1) complete evaporation of a liquid sample in a sample chamber, and 2) allowing the sample vapor in the sample chamber to equilibrate for a predetermined time. An inert carrier gas (e.g., dry nitrogen or zero air) is also admitted to the sample chamber. After equilibration, the sample vapor is admitted as a conditioned sample to an analysis instrument. Preferably, the predetermined equilibration time is sufficiently long that the sample vapor in the sample chamber becomes substantially homogeneous with respect to both concentration and isotopic ratio. Vapor derived from a liquid calibration standard in this manner can be employed as an accurate gas-phase calibration reference.

Abstract: Improved optical alignment precision to a passive optical cavity is provided by including a combination of a weak focusing element and a translation plate in the input coupling optics. Adjustment of positions and angles of these optical elements, preferably after all other input optical elements are fixed in place, advantageously provides for high-precision optical alignment to the cavity, without requiring excessively tight fabrication tolerances. Fabrication tolerances are relaxed by making the optical power of the weak focusing element significantly less than the optical power of a strong focusing element in the input optics. The position and angles of the beam with respect to the cavity can be adjusted, as can the size of the beam at the cavity. Differential adjustment of the beam size in two orthogonal directions (e.g., tangential plane and sagittal plane) at the cavity can also be provided.

Abstract: Preparation methods for introducing liquid samples to gas analysis instruments include 1) complete evaporation of a liquid sample in a sample chamber, and 2) allowing the sample vapor in the sample chamber to equilibrate for a predetermined time. An inert carrier gas (e.g., dry nitrogen or zero air) is also admitted to the sample chamber. After equilibration, the sample vapor is admitted as a conditioned sample to an analysis instrument. Preferably, the predetermined equilibration time is sufficiently long that the sample vapor in the sample chamber becomes substantially homogeneous with respect to both concentration and isotopic ratio. Vapor derived from a liquid calibration standard in this manner can be employed as an accurate gas-phase calibration reference.

Abstract: The present invention relates to the separation, quantitative measurement, and analysis of trace species using a combination of three steps in succession. First, trace species are separated from other species that are present. Second, the trace species are chemically modified to convert them into specific species that are advantageous for the third and final step. In this last step, cavity enhanced optical detection of the converted species is performed to detect and measure the concentrations of the species of interest. Because the last step has spectroscopic resolution, the concentration of isotopologues in each converted species can be determined. Further processing can provide the ratios between pairs of isotopologues, in particular the ratio of the rare isotopologues to the most abundant isotopologue.

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 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 optical alignment precision to a passive optical cavity is provided by including a combination of a weak focusing element and a translation plate in the input coupling optics. Adjustment of positions and angles of these optical elements, preferably after all other input optical elements are fixed in place, advantageously provides for high-precision optical alignment to the cavity, without requiring excessively tight fabrication tolerances. Fabrication tolerances are relaxed by making the optical power of the weak focusing element significantly less than the optical power of a strong focusing element in the input optics. The position and angles of the beam with respect to the cavity can be adjusted, as can the size of the beam at the cavity. Differential adjustment of the beam size in two orthogonal directions (e.g., tangential plane and sagittal plane) at the cavity can also be provided.

Abstract: A phasor can be employed within the resonator of an optical parametric oscillator (OPO) to adjust the absolute and relative phase of OPO beams. An embodiment of the invention comprises an OPO having at least one phasor for receiving and adjusting the phase of one or more beams resonating within the optical cavity which forms part of the OPO. Smooth alteration of the phases of the OPO beams using the at least one phasor facilitates continuous tuning of the wavelength of at least one of the beams. In another embodiment, the at least one phasor may be a translatable wedge or have adjustable refractive index to alter the phases of the OPO beams. In an additional embodiment, each at least one phasor may be comprised of more than one material, held fixedly together.

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: A cavity-enhanced spectrometer light source comprises: i) an electrically pumped SCDL having first and second facets at least said first facet being anti-reflection coated, ii) a diffraction grating facing said first facet, iii) a collimating lens interposed between said facet and said diffraction grating, iv) means for translating said lens substantially perpendicular to the path of the light beam transmitted from said SCDL to said diffraction grating to provide coarse tuning of the emission wavelength of said SCDL, and v) means for altering at least one of the temperature of and current to said SCDL to provide fine tuning of the emission wavelength of said SCDL.

Abstract: Improved multipass second harmonic generation (SHG) is provided by the use of an inverting, self-imaging telescope which ensures parallelism of all passes of all beams within the nonlinear medium. Improved multipass SHG is also provided by the use of a wedged phasor which provides a simple adjustment of the relative phase of the pump beam and second harmonic beam between passes. Improved multipass SHG is provided by the use of an inverting self-imaging telescope in combination with a wedged phasor which provides a simple adjustment of the relative phase of the pump beam and second harmonic beam between passes, ensures parallelism of all passes of all beams within the nonlinear medium. A further embodiment includes an OPO and at least one phasor and preferably first and second telescope assemblies.

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: 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).