Mid-Infrared Generated Laser-Induced Grating Signals in Methane-Containing Gas Mixtures as Indicators of Composition, Pressure, and Temperature.

The present work is aimed at studying how spatially periodic modulations of the refractive index of the medium, i.e., laser-induced gratings (LIGs), generated in a gas mixture containing methane (CH) by nanosecond pulses of resonant mid-infrared laser radiation, can be used to measure various gas parameters.

Two-color four-wave mixing contribution to an electrostrictive laser-induced grating signal in CO-N mixtures and gas diagnostics.

Multiparameter determination in the gas phase using the versatile laser-induced grating (LIG) technique is a challenging task due to interdependence of observables on multiple thermodynamic parameters. In - mixtures, simultaneous determination of species concentration and gas temperature can be achieved by using an additional concentration-dependent contribution to the LIG signal, which appears if 1064 nm pump pulses are employed. This contribution can be attributed to a direct, quasi-resonant two-color four-wave mixing (TCFWM) of the pump and probe radiations in .

Two-color four-wave mixing contribution to an electrostrictive laser-induced grating signal in CO-N mixtures and gas diagnostics: publisher's note.

This publisher's note corrects content in Appl. Opt.62, 8115 (2023)APOPAI0003-693510.

Coherent Anti-Stokes Raman Scattering Measurements of Time and Length Scales of Temperature Fluctuations in a Turbulent Flame.

The ability to derive temporal and spatial scales of "instantaneous" local temperature variations in a turbulent flame by means of coherent anti-Stokes Raman scattering (CARS) spectroscopy is demonstrated, for the first time to our knowledge. The measurements employed two CARS spectrometers with synchronized nanosecond pulse-repetitive lasers. The system was enabling to record, with a high temporal resolution of about 10 ns, series of single laser shot CARS spectra of N molecules from two spatially overlapped or displaced probe volumes as small as 0.

Three-color vibrational CARS thermometry of fuel-rich ethylene/air flames using a potassium gadolinium tungstate Raman-active crystal as a source of narrowband probe radiation.

Three-color broadband vibrational coherent anti-Stokes Raman scattering (CARS) temperature measurements were carried out in laminar fuel-rich sooting ethylene/air flames. Stimulated Raman scattering (SRS) of a picosecond pump laser pulse in a Raman-active potassium gadolinium tungstate [KGd(WO)] crystal was employed as a source of narrowband probe radiation. In the three-color CARS experiment, this wavelength-shifted radiation enables N-based vibrational CARS temperature measurements in sooting flames free of the signal interference with the absorption/emission bands of the flame intermediate radicals C.

Simultaneous measurement of speed of sound, thermal diffusivity, and bulk viscosity of 1-ethyl-3-methylimidazolium-based ionic liquids using laser-induced gratings.

The technique of laser-induced gratings (LIGs) has been applied to the simultaneous determination of speed of sound and thermal diffusivity of four 1-ethyl-3-methylimidazolium ([EMIm])-based room temperature ionic liquids (RTILs)-[EMIm][N(CN)2], [EMIm][MeSO3], [EMIm][C(CN)3], and [EMIm][NTf2]-at ambient pressure (1 bar (0.1 MPa)) and temperature (28 °C (301 K)). Transient laser-induced gratings were created as a result of thermalization of a quasi-resonant excitation of highly lying combinational vibrational states of the RTIL molecules and electrostrictive compression of the liquid by radiation of a pulse-repetitive Q-switched Nd:YAG pump laser (1064 nm).

Determination of physicochemical parameters of ionic liquids and their mixtures with solvents using laser-induced gratings.

The laser-induced gratings (LIGs) technique has been applied for the simultaneous determination of sound speed and thermal diffusivity in the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethylsulfate, [EMIm][EtSO(4)], its mixture with 85.68 mol % acetone, C(3)H(6)O, and pure acetone. The measurements have been performed in a quartz glass cuvette at ambient pressure and temperature.

Broadband time-domain absorption spectroscopy with a ns-pulse supercontinuum source.

A Q-switched laser based system for broadband absorption spectroscopy in the range of 1390-1740 nm (7200-5750 cm(-1)) has been developed and tested. In the spectrometer the 1064 nm light of a 25 kHz repetition-rate micro-chip Nd:YAG laser is directed into a photonic crystal fiber to produce a short (about 2 ns) pulse of radiation in a wide spectral range. This radiation is passed through a 25 km long dispersive single-mode fiber in order to spread the respective wavelengths over a time interval of about 140 ns at the fiber output.

Two-photon stimulated Raman excitation of thermal laser-induced gratings in molecular gases using broadband radiation of a single laser.

For the first time to our knowledge, thermal laser-induced gratings (LIGs), generated via two-photon stimulated Raman excitation of pure rotational (and low-lying vibrational) transitions in molecules employing broadband radiation of a single pump laser, are observed. The efficiency of LIGs excitation using a few ns pulse duration dye laser with the spectral width of about 400 cm(-1), which covers the frequency range of the characteristic rotational transitions, is experimentally investigated in a number of molecular gases (N(2), CO(2), C(3)H(8)) at room temperature and pressures of 0.1-5 bar.

Time-resolved measurement of the local equivalence ratio in a gaseous propane injection process using laser-induced gratings.

For the first time laser-induced gratings (LIGs) have been used for the investigation of a non-stationary pulse-repetitive injection process of gaseous propane, C(3)H(8), into air. By recording and evaluating single-shot LIG signals it was possible to determine, on a cycle-averaged basis, the temporal evolution of the local (within a probe volume 300 microm in diameter and 10 mm in length) equivalence ratio and by this the fuel-air ratio. Two different data treatment strategies, subject to C(3)H(8) concentration range, were first tested at stationary conditions and then used to evaluate the LIG signals obtained during the injection process.