A novel quartz enhanced photoacoustic spectroscopy (QEPAS) trace gas detection scheme is reported in this paper. A cylindrical lens was employed for near-infrared laser focusing. The laser beam was shaped as a planar line laser between the gap of the quartz tuning fork (QTF) prongs. Compared with a spherical lens-based QEPAS sensor, the cylindrical lens-based QEPAS sensor has the advantages of ...

The properties of semiconductor laser diodes for trace gas measurements are reviewed. First, the modulation characteristics of these lasers are discussed. Then, two sensitive spectroscopic methods using a frequency-modulated near-IR laser are presented and their performance compared. In the λ = 2 μm range, second-harmonic optical detection has shown a 20 times better detection limit than photoa...

CASE REPORT A twenty three year old woman was diagnosed of a morning glory papillary anomaly, then with normal visual acuity (VA). Nine years later, the VA decreased to 0.4, secondary to a serous macular detachment, confirmed by optical coherence tomography (OCT). After treatment with C2F6 gas injection, positioning, and peripapillary laser, the VA improved to 0.7 and the foveolar area reattach...

The use of lasers during surgery in the airway of the horse bears various hazards of which airway combustion is the most severe. This risk is of particular concern in anesthetized animals breathing an oxygen-rich gas mixture. Though total intravenous anesthesia has been commonly advocated for laser procedures, laser surgery in the airway of the horse can be performed more safely under inhalatio...

We demonstrate a minimally invasive nuclear magnetic resonance (NMR) technique that enables determination of the surface-area-to-volume ratio (S/V ) of soft porous materials from measurements of the diffusive exchange of laser-polarized Xe between gas in the pore space and Xe dissolved in the solid phase. We apply this NMR technique to porous polymer samples and find approximate agreement with ...

Gas-phase laser Raman spectroscopy has recently been adopted to determine the concentrations of relevant gaseous species within the anode flow channel with high spatial and temporal resolution during operation at technically relevant operating conditions. The paper describes the configuration of an optically accessible SOFC, the laser system and optical setup for 1 D Raman spectroscopy as well ...

Simultaneous imaging of laser-induced fluorescence of toluene and 3-pentanone was used to determine the local absolute oxygen and residual gas concentrations present within an engine. The technique utilizes the different sensitivities of the laser-excited molecules to quenching by molecular oxygen as a means to determine quantitative images of in-cylinder oxygen concentrations. The difference i...

We investigate beam pointing dynamics in filamentation in gases driven by high repetition rate femtosecond laser pulses. Upon sudden exposure of a gas to a kilohertz train of filamenting pulses, successive filaments are steered from their original direction to a new stable direction whose equilibrium is determined by a balance among buoyant, viscous, and diffusive processes in the gas. The beam...

When performing laser-induced plasma spectroscopy for elemental analysis, the analyte signal-to-noise ratio increased from four to over fifty if the plume was reheated by a dye laser pulse tuned to resonant absorption. Time-resolved studies showed that the enhancement was not due to resonance photoionization. Rather, efficient and controlled rekindling of a larger plume volume was the key mecha...

Any book on classical optics has an important chapter on the characteristics of polarized light and its propagation in physical media. Experiments with polarizedlight have also greatly contributed to the understanding of the structure of atoms, molecules and matter. The advent of the laser has brought about a revival of optics,· mainly because it made available light sources of extremely high i...