High-energy normal-dispersion fiber optical parametric chirped-pulse oscillator.

We demonstrate a fiber optical parametric chirped-pulse oscillator (FOPCPO) pumped in the normal-dispersion regime by chirped pulses at 1.036 µm. Highly chirped idler pulses tunable from 1210 nm to 1270 nm with energies higher than 250 nJ are generated from our system, along with signal pulses tunable from 870 nm to 910 nm.

Coupling a Rapid-Scan FT-IR Spectrometer with Quantum Cascade Lasers within a Single Setup: An Easy Way to Reach Microsecond Time Resolution without Losing Spectral Information.

For the first time, a standard rapid-scan Fourier-transform infrared (FT-IR) spectrometer was coupled with quantum cascade lasers (QCLs) tunable within the 1876-905 cm spectral range, within one single setup, by keeping one single sample compartment. The aim was to extend the time resolution of absorption measurements by several orders of magnitude thanks to the fast pulsed QCL technology without losing the spectral information provided by standard FT-IR spectroscopy, both probing the same sample. By slightly modifying the optical bench arrangement, the spectrometer now enables a fast and easy switch between the standard FT-IR mode, used for classical broadband scans from 6000 to 650 cm, and the new QCL-irradiation mode, used for ultrafast recording at specific wavenumbers (the two diagnostics have superimposed beam paths).

Measurements and modeling of acetone laser-induced fluorescence with implications for temperature-imaging diagnostics.

Recent determinations of the temperature dependence of acetone fluorescence have permitted the application of acetone planar laser-induced fluorescence imaging, which was already popular for mapping concentration, to the measurement of temperature. With a view toward developing temperature-imaging diagnostics, we present atmospheric-pressure fluorescence and absorption results acquired with excitation at eight wavelengths across the absorption feature of acetone and at temperatures from 300 to 1000 K. Modeling of the fluorescence yield of acetone is shown to be useful in explaining both these results and the variation of acetone fluorescence with pressure and composition that was observed in several studies.

Temperature imaging with single- and dual-wavelength acetone planar laser-induced fluorescence.

Two sensitive techniques for temperature imaging by use of acetone planar laser-induced fluorescence, applicable at temperatures up to 1000 K, are introduced and demonstrated. Photophysics data on the wavelength-dependent temperature variation of acetone fluorescence permit the implementation of a single-wavelength technique in environments with constant pressure and constant acetone mole fraction, and a dual-wavelength method can be applied in flows with mixing and (or) chemical reaction. Preliminary imaging results are presented for acetone-air flow over a heated cylinder (single-wavelength strategy) and for a heated laminar jet (dual-wavelength strategy).