Stimulated Raman Scattering Lines Research Articles

Spectral and temporal properties of 5-phenyl-2-[4-(5-phenyl-1,3-oxazol-2-yl)phenyl]-1,3-oxazole (POPOP) multiphoton-excited luminescence

The results of a study of multiphoton-excited luminescence and Stimulated Raman scattering (SRS) of POPOP in a form of crystalline powder and toluene solution are presented. Two-photon and three-photon-excited luminescence in POPOP crystalline powder and toluene solution was registered under excitation by pico- and nanosecond laser pulses. Samples cooling to the temperature of liquid nitrogen leads to the appearance of an additional line in the luminescence spectrum at a wavelength of 447 nm, SRS lines intensity increasing accompanying two-photon luminescence process and changing temporal dynamics, a decrease in the contribution of the fast component in the decay time curve.

Generation of dual-supercontinuum coherent radiation in acetone mixed with carbon disulfide by stimulated Raman scattering.

Stimulated Raman scattering (SRS) in a liquid has been a major focus of nonlinear optics. Traditional SRS generates single or cascaded Stokes components arising from spontaneous Raman noise. Herein, we report the formation mechanism of a specific spectrum-continuous spectroscopy technique based on SRS of mixed liquids. SRS of a mixed acetone and carbon disulfide solution is investigated by a pulsed Nd:YAG laser with a wavelength of 532 nm. Two remarkably asymmetric broadened SRS lines are obtained. When the volume ratio is 7:3, the broadened spectral bands are optimized. The supercontinuum spectroscopy phenomenon is explained by hydrogen bond formation, adjacent vibrational modes coupling, and laser-induced plasma generation. This technique has the potential to contribute to the development of a supercontinuum Raman laser.

Nanoshock wave resonance enhancement on stimulated Raman scattering of H(2)O(2) in liquid water.

This study investigates the stimulated Raman scattering (SRS) of H(2)O(2)-H(2)O mixtures. The laser-induced plasma nanoshock wave is formed by focusing an intense pulsed 532 nm laser beam on the mixtures. An enhancement at the low-frequency 1715 cm(-1) SRS line of the bending mode of H(2)O(2) is observed. The mechanism of enhancement was attributed to nanoshock wave resonance with the bending mode, which would preferentially excite phonon and lower energy molecular vibrations.

Estimating the pressure of laser-induced plasma shockwave by stimulated Raman shift of lattice translational modes

The current paper investigates stimulated Raman scattering (SRS) when laser-induced plasma is formed in heavy water by focusing an intense pulsed 532 nm Nd:YAG laser beam at room temperature. An unexpected low-frequency SRS line attributed to the lattice translational modes of ice-VII (D2O) is observed. The pressure of the plasma shockwave is estimated using low-frequency SRS line shift.

Stimulated Raman scattering of lattice translational modes in liquid heavy water

A study was conducted on stimulated Raman scattering (SRS) when laser-induced plasma is formed in heavy water by focusing an intense picosecond pulsed Nd:YAG laser beam with wavelength 532 nm at room temperature. An unexpected 280 cm(-1) low frequency SRS line attributed to the lattice translational modes is observed. This SRS line and the internal-mode SRS lines indicate that the ice VII structure is formed in heavy water under the condition of laser-induced shockwave production.

Investigation of amplification process on the third Stokes line of H_2 under ultraviolet laser irradiation

An amplification process was investigated in the third stimulated Raman scattering (SRS) line of H2 excited with a 266 nm laser beam generated from the fourth harmonic of a Nd:YAG laser. The unexpected intensity enhancement observed at the third Stokes SRS line around 397.8 nm is attributed to the seeding of the self-generated H-epsilon Balmer line at 397 nm of atomic hydrogen by pumping the H2 molecule with a high-energy laser pulse at 266 nm. It is worth mentioning that in our case the SRS spectrum of H2 showed a quite different intensity pattern from the usual SRS spectra of hydrogen. The pulse energy and pressure dependence of all the SRS lines in general and the third Stokes SRS line in particular were investigated, and in all respects the amplified SRS line at 397.8 nm manifested completely different characteristics that have not been reported in previous publications. The conversion efficiency (CE) of all the SRS lines in the hydrogen 266 nm SRS spectrum was also estimated, and 36% CE was achieved at the 397.78 nm line. To support our claim for amplification at the third Stokes line by seeding of the H-epsilon Balmer line of atomic hydrogen, a comparative study was also carried out by pumping hydrogen gas with 355 nm (less energy per photon) and 266 nm laser beams. It is worth noting that amplification of the third Stokes SRS line was observed only with the 266 nm pump laser, where dissociation of H2 and excitation of atomic hydrogen take place, and not with the 355 nm pump laser.

Enhanced stimulated Raman scattering in H2 by seeding an SRS line into an H-ɛ Balmer line: Amplification-coupled laser wavelength shifter

The stimulated Raman scattering (SRS) in H2 gas above the dissociation energy limit was recorded using a 266-nm UV laser. All of the observed Stokes and anti-Stokes SRS lines showed a normal behavior except the third Stokes SRS lines at 397.8 nm, which showed a substantial intensity enhancement of about a 36%-conversion efficiency of the pump energy. This enhancement in the SRS line is attributed to the seeding of the SRS line into the Balmer H-ɛ line at 397 nm in molecular hydrogen. To the best of our knowledge, there is no report of any work on enhanced stimulated Raman scattering in H2 by the seeding of the H-ɛ Balmer line into the SRS line and attaining a very high intensity at the third Stokes SRS lines at 397.8 nm. The cell pressure and the laser pulse energy dependence of these SRS lines substantiate our explanation.

Stimulated Raman scattering from individual single-wall carbon nanotubes

Individual single-wall carbon nanotubes (SWNTs) exhibited continuous-wave stimulated Raman scattering (SRS). The Raman gain is a few orders higher, and the threshold power is a few orders lower, than values ever reported for other bulk materials and is explained as the result of both the large nonlinear property and efficient electron-phonon interaction in the SWNT. The laser-induced variation of the peak position of the SRS line was likely to depend on the linewidth or tube quality. The results demonstrate the high potential of SWNTs in applications of nanoscale nonlinear optical devices such as wide-range tuneable Raman lasers.

Investigation of stimulated Raman scattering of ν1 and ν2 modes in CH 4

Using 355 nm excitation laser radiation, the stimulated Raman scattering (SRS) lines of methane between 14 000 and 26 000 cm −1 at different experimental conditions were recorded. Two sets of successive SRS lines manifesting the Raman shift in the ν 1 and ν 2 modes of vibration in the 1A 1 electronic state of CH 4 have been assigned. The evolution of SRS lines at different pressures has been investigated. The energy dependence of SRS lines has revealed that SRS line due to higher order components become stronger than the fundamental at higher laser pump energy.

Non-linear optical investigations of glass structure

Non-linear spectroscopy, including stimulated Raman scattering (SRS), has been proposed for the experimental verification of modern color center models in silica glasses. The selection rules in spontaneous and stimulated Raman processes were identical; however, the shape and enormous intensity of SRS lines in silica optical fibers (OFs) are determined by the threshold nature of SRS. The observed SRS spectra in OFs consisted of a number of narrow lines, due to silica network vibrations, to dopant and ‘microdefects’ also and more than 20 overtones and combination vibrations. The anharmonicity constant, χ, and frequencies of harmonic vibrations are calculated using the multiwavelength SRS in OFs for the first time. It is shown that the minimal anharmonicity is characteristic for deformation vibrations of silica tetrahedrons with Δv = 440 cm −1. The χ values for the ‘microdefect’ vibrations in silicate and doped phosphate groups were greater by ∼ 2 and ∼ 8 times, respectively, than the χ values for 440 cm −1 silica vibrations. The different interactions between ‘silica’ or ‘phosphate’ microdefects and the bath of silica vibrations are established. It is emphasized that the SRS possesses the simple and universal character for express-analytical investigations of type, concentrations and spatial distributions of dopant and microdefects in any transparent glass media, which could be manufactured as OFs with optical losses no greater than ∼ 100 dB/km. The future application of SRS in OFs as an experimental tool for investigation of the changes in glass structure under mechanical stresses, irradiation and thermal annealing are indicated.

Stimulated Raman scattering conversion of radiation from an electric-discharge XeCl laser

An investigation was made of the conversion of XeCl laser radiation (λ~3O8 nm) by stimulated Raman scattering (STRS) in compressed gases. Eleven Raman scattering lines in the ultraviolet and visible parts of the spectrum were obtained in hydrogen, methane, and a mixture of these. It was found that by altering the experimental conditions (gas pressure, pump power, focusing) the energy distribution of the converted radiation over the STRS lines could be controlled. Calculations are made of STRS cross sections of various gases.