D. Lancaster

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High-sensitivity detection of formaldehyde (CH2O) at 3.5315 micrometers (2831.64 cm-1) is reported with a diode-laser-pumped, fiber-coupled, periodically poled LiNbO3 spectroscopic source. This source replaced the Pb-salt diode laser Dewar assembly of an existing tunable diode-laser absorption spectrometer designed for ultrasensitive detection of CH2O.(More)
The development and characterization of a compact mid-infrared source for high-resolution spectroscopic detection of trace gases such as methane and water vapor at 3.3 µm in ambient air is reported. This source utilizes difference frequency generation (DFG) in a periodically poled LiNbO 3 (PPLN) crystal pumped by two single-frequency diode lasers. A maximum(More)
Real-time detection and measurement of sub-ppm levels of formaldehyde in ambient air using diode-pumped 3.5 µm difference-frequency generation (DFG) in periodically poled LiNbO 3 (PPLN) is reported. Minimum detectable concentration of 30 ppb was achieved with a compact , portable room-temperature gas sensor configured for formaldehyde (H 2 CO) detection.(More)
Carbon monoxide (CO) has been implicated as a biological messenger molecule analogous to nitric oxide. A compact gas sensor based on a midinfrared laser absorption spectroscopy was developed for direct and real-time measurement of trace levels (in approximate pmol) of CO release by vascular cells. The midinfrared light is generated by difference frequency(More)
The implementation and application of a portable fiber-coupled trace-gas sensor for the detection of several trace gases, including CO2, CH4, and H2CO, are reported. This particular sensor is based on a cw fiber-amplified near-infrared (distributed Bragg reflector) diode laser and an external cavity diode laser that are frequency converted in a periodically(More)
Amongst its many features, MPI-2 offers the first standard high-performance I/O interface. While this enables a parallel and I/O intensive code to run on multiple platforms, achieving consistent performance levels will be more difficult than many users imagine. To better understand the I/O performance issues in MPI-2, fecit and Southampton have developed a(More)
Continuous-wave mid-infrared radiation near 3.5 mm is generated by difference-frequency mixing of the output of a compact 1.1 1.5-mm dual-wavelength f iber amplif ier in periodically poled LiNbO 3. The diode side-pumped amplif ier is constructed with double-cladding Yb-doped f iber followed by single-mode Er/Yb codoped f iber. Output powers of as much as 11(More)
Tunable narrowband mid-infrared radiation from 3.25 to 4.4 micrometers is generated by a compact fiber-coupled, difference-frequency-based spectroscopic source. A 20-mW external cavity diode laser (with a tuning range from 814 to 870 nm) and a 50-mW distributed-Bragg-reflector diode-laser-seeded ytterbium-doped fiber amplifier operating at 1083 nm are(More)
  • L Adhianto, B Chapman, D Lancaster, I Wolton, M Leuschel, A Kneer
  • 2001
In recent y ears, methods for analyzing and parallelizing sequential code using dependence analysis and loop transformations have b e e n d e v eloped. These techniques have p r o ved successful, and have been used either to move from sequential to parallel codes, or to improve the eeciency of existing parallel codes. Our research focuses on Fortran code(More)
The photosensitivity of highly Er/Yb doped and undoped phosphate glass fibers is characterized under irradiation with intense pulsed 193 nm light from an ArF excimer laser through a phase mask. The ultraviolet photosensitivity of the active fibers is shown to be roughly half that of the passive fibers. We also demonstrate that the strong growth of the fiber(More)