Coherent anti-stokes raman scattering microscopy in the presence of electromagnetic confinement

The optical response used in studies of coherent anti-Stokes Raman scattering (CARS) microscopy can be enhanced or suppressed by means of electromagnetic confinement. In this paper, an approach based on planar mirrors is presented. Because of the classical origin of such a nonlinear optical effect, the theory is developed within a fully classical framework and it turns out that the CARS signal can be modified in a fashion similar to what has been extensively investigated for equivalent alterations of incoherent signals understood in terms of cavity quantum electrodynamics.     

Absolute determination of the nonlinear susceptibilityχ3 via two-beam nonlinear interferometry

A two-beam nonlinear interferometric technique is described whereby the amplitude and sign of both the real and imaginary parts of the nonlinear susceptibility _χ3 may be determined. Moreover, this technique permits an extremely precise determination of the electronic and molecular contributions to _χ3. Hence, we ascertain the electronic fraction of the Kerr constants of CS₂ and C₆H₆ to be 12.7 ± 1.1% and 19.8 ± 0.8%, respectively. These results provide a basis for the comparison of nonlinear refractivity and frequency-mixing measurements in these materials and an accurate means for the absolute calibration of a variety of measurements of _χ3.     

Experimental study of vibrational and pure rotational coherent anti-stokes Raman scattering (CARS) in molecular hydrogen

Using a specially designed excimer-laser-pumped dye laser of adjustable bandwidth high-lying pure rotational transitions of both, ortho-and para-hydrogen have been identified by coherent anti-Stokes Raman scattering (CARS). As an interesting application H₂-based CARS-thermometry is discussed.     

Temperature and concentration measurements of molecular hydrogen in a filamentary discharge by coherent anti-stokes raman spectroscopy (CARS)

Coherent anti-Stokes Raman Spectroscopy (CARS) is applied to a filamentary discharge in H₂. Temperature and density profiles of molecular hydrogen are determined. The maximum temperature observed on the discharge axis is 5685 K. Vibrational and rotational transitions are analyzed and a difference in the evaluated temperatures is found which increases with pressure. In addition, the reactive thermal conductivity associated with dissociation is determined and compared with earlier work.     

Coherent radiation generation in (7.9÷8.7) μm and (11÷14) μm regions by rotational raman scattering in deuterium

Summary Stimulated rotational Raman scattering of CO₂ laser radiation in ortho-D₂ provides a high-power coherent source in the infrared region from 11 to 14 μm. A peak output energy of ≃1 J has been obtained for a pump energy of 4.0 J. Threshold energies have been compared with those of para-H₂ measured in the same apparatus and experiment scaling factors are discussed.

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Riassunto Lo scattering Raman rotazionale stimolato della radiazione laser a CO₂ in orto-deuterio fornisce una sorgente coerente di alta potenza nella regione dell'infrarosso tra 11 e 14 μm. Con un'energia di pompa dell'ordine di 4 J si ottiene un'energia di 1 J. Le energie di soglia sono state confrontate con quelle del para-idrogeno, misurate nello stesso apparato, e i fattori di scala sperimentali sono discussi.

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Резюме Вынужденное вращательное Рамановское рассеяние излучения CO₂ лазера в орто-D₂ представляет когерентный источник высокой интенсивности в инфракрасной области от 11 до 14 мкм. Получается максимум энергии на выходе ≃1 Дж для энергии накачки 4.0 Дж. Пороговые энергии сравниваются с данными, измеренными той же аппаратурой, в случае пара-H₂. Обсуждаются экспериментальные масштабные факторы.

     

A raman scattering study of the phase transition in the ammonium oxyfluoride (NH4)3TiOF5

Raman spectra of a polycrystalline sample of the perovskite-like oxyfluoride (NH₄)₃TiOF₅ are measured in the frequency region 100–3600 cm^?1 at temperatures ranging from 91 to 370 K under hydrostatic pressures of up to 9 GPa, which include the range of the phase transition from the orientationally disordered cubic phase to the low-symmetry phase. Anomalies in the spectral parameters due to the phase transition are revealed in the range of vibrations of TiOF₅ octahedral groups.     

High resolution nonlinear spectroscopy. Dicke narrowing and dispersion of the third-order nonlinear susceptibility of H2 near the Q01 (1) vibrational resonance

The forward scattering process of motional narrowing in hydrogen gas has been investigated by an original method of nl spectroscopy of general application. The method has allowed a detailed study of the dispersion of the nl susceptibility χ⁽³⁾(ω) showing an unexpected behavior of χ⁽³⁾(ω)' near the Q₀₁ (1) molecular eigenfrequency.     

Applications of electronic speckle interferometry (ESI) techniques for spacecraft structural components

Laser-based electronic speckle interferometry (ESI) techniques, viz., electronic speckle pattern interferometry (ESPI) and electronic speckle shearographic interferometry (ESSI) are used for testing of spacecraft structural components. The combined ESPI and ESSI system developed in house was successfully used for the non-destructive evaluation (NDE) of honeycomb sandwich panels and propellant tanks of Indian Space Research Organization (ISRO). Debonds between face sheet and the honeycomb core were identified using (i) thermal and (ii) dual vacuum stressing methods. On-line NDE of the propellant tanks under internal pressure loading for identification of the minute cracks and thickness reduction areas were successfully implemented by ESI.     

Measurement of polarization dependence of nonlinear susceptibility responsible for Rayleigh-wing and Brillouin scattering

By using a simple optical geometry based on backward light scattering and employing a Sandercock-type tandem Fabry-Perot interferometer, we measure both the linear and the circular polarization dependences of Rayleigh-wing and Brillouin scattering in a sample of liquid-crystal 4-n-pentyl-4'-cyanobiphenyl. Observed polarization dependences are consistent with the third-order nonlinear susceptibilities, taking into account the traceless symmetric scattering tensor for Rayleigh-wing scattering and the isotropic scattering tensor for Brillouin scattering.     

Test of an optical parametric oscillator (OPO) as a compact and fast tunable stokes source in coherent anti-stokes raman spectroscopy (CARS)

An optical parametric oscillator (OPO), as a novel kind of broadband Stokes source, is employed for coherent anti-Stokes Raman spectroscopy (CARS). Compared to the conventional dye laser configuration OPO-CARS offers practical advantages. The tunable OPO allows a fast and comfortable frequency tuning. The excitation bandwidth of about 35 cm^–1 (FWHM) limits the spectral range of effective and stable single pulse CARS generation but can be used to enhance selected spectral structures.     

Ratios of the real to imaginary part of the p 4He and pn elastic scattering amplitudes at 0.7 GeV

The ratios ρ _p He and ρ _pn of the real to imaginary part of the forward proton-⁴He and proton-neutron elastic scattering amplitudes have been determined from the data on proton-helium elastic scattering cross sections at 0.7 GeV in the Coulomb-nuclear interference region to be ρ _p He =?0.06±0.06 and ρ _pn = ?0.28±0.12. The existing experimental values of ρ _p He are compared in a wide range of energies with the corresponding values calculated by means of the Glauber model using the ratios ρ _pp and ρ _pn evaluated with the help of the dispersion relations.     

Experimental investigation of the two-photon widths of the chi(c0) and the chi(c2) mesons

Using 12.7 fb(-1) of data collected with the CLEO detector at CESR, we observed two-photon production of the cc states chi(c0) and chi(c2) in their decay to pi(+)pi(-)pi(+)pi(-). We measured gamma(gammagamma)(chi(c))xB(chi(c)-->pi(+)pi(-)pi(+)pi(-)) to be 75+/-13(stat)+/-8(syst) eV for the chi(c0) and 6.4+/-1.8(stat)+/-0.8(syst) eV for the chi(c2), implying gamma(gammagamma)(chi(c0)) = 3.76+/-0.65(stat)+/-0.41(syst)+/-1.69(br) keV and gamma(gammagamma)(chi(c2)) = 0.53+/-0.15(stat)+/-0.06(syst)+/-0.22(br) keV. Also, cancellation of dominant experimental and theoretical uncertainties permits a precise comparison of gamma(gammagamma)(chi(c0))/gamma(gammagamma)(chi(c2)), evaluated to be 7.4+/-2.4(stat)+/-0.5(syst)+/-0.9(br), with QCD-based predictions.