Multimodal Raman

Farrow R. L., Rahn L. A. Interpreting coherent anti-Stokes Raman spectra measured with multimode Nd YAG pump lasers, J. Opt. Soc. Am. B2, 903-7 (1985). 

Written by an international panel of experts, this volume begins with a comparison of nonlinear optical spectroscopy and x-ray crystallography. The text examines the use of multiphoton fluorescence to study chemical phenomena in the skin, the use of nonlinear optics to enhance traditional optical spectroscopy, and the multimodal approach, which incorporates several spectroscopic techniques in one instrument. Later chapters explore Raman microscopy, third-harmonic generation microscopy, and nonlinear Raman microspectroscopy. The text explores the promise of beam shaping and the use of a broadband laser pulse generated through continuum generation and an optical pulse shaper. 

Theoretical IR intensities of the fundamental, overtone, and combination transitions in furan (as well as pyrrole and thiophene), obtained by MULTIMODE and second-order perturbation calculations, have been compared with experimental data <2004PCP340>. IR and FT-Raman spectra, combined with BPW9I/6-3II4-G calculations, show that the a -forms of 5-(4-bromophenyI)furan-2-carbaIdehyde <2003MI2I3> and 5-(4-fluorophenyl)furan-2-carbaldehyde <2002MI235> are preferred over the respective ry -forms. 

To determine the unconditional probability distribution for the spin-wave excitations Psw(n), we must find the effective number of transverse modes which contribute to the Raman processes. We identify two extreme regimes which permit analytic treatment a single mode regime where the number of excitations in the 87Rb cell follows Bose-Einstein (thermal) statistics and a multimode regime where it follows Poisson statistics. We find in both cases that the quantities F and Q depend on two experimental parameters 0 ( number of lost Stokes photons) and v ( noise to signal ratio), which are defined in Tab. 1. 

Kroll, S., Alden, M., Berglind, T., and Hall, R. J. "Noise Characteristics of Single Shot Broadband Raman-Resonant CARS with Single- and Multimode Lasers." Applied Optics 26, no. 6 (1987). 

The analysis of MDA-MB-231 cells incubated with 53 was also carried out on a synchrotron-based multiple beam FT-IR imaging (IRENI) set up at the Synchrotron Radiation Center, Stroughton, Wisconsin, equipped with a FPA detector of 96 X 96 pixels, where each pixel corresponds to a 0.54 x 0.54 pm area of the sample. With the better resolution afforded by this technique, the complex appears heterogeneously distributed in the cell, but with a higher perinuclear concentration [79]. In addition, 53 was mapped in cell by SR-UV-SM (synchrotron radiation UV spectromicroscopy), confocal Raman microscopy, and AFM-IR (see Sections 11.3.3 and 11.3.4). Thus, this innovative family of complexes appeared to be a valuable multimodal (and not only bimodal) tool for cell imaging. 

Pages O, Tite T, Chafi A et al (2006) Raman study of the random ZnTe-BeTe mixed crysttil percolation model plus multimode decomposition. J Appl Phys 99 063-507 Ohtomo A, Kawasaki M, Koida T et al (1998) MgxZni xO as a 11-VI widegap senuconductor alloy. Appl Phys Lett 72 2466-2468... 

Fig. 2. Structural characterization of SWNT multilayers, (a) Sequential UV-vis spectra of a glass substrate in the course of the LBL deposition of SWNT. The spectra were taken for a total number of (PEFSWNT) bilayers indicated in the graph, (b) Raman scattering spectra of SWNT dispersion (1), LBL film on a glass substrate (2) and free-standing film (3). (c) Tapping mode AFM image (DI, multimode IIIA) of a Si wafer bearing (PEI/PAAXPEI/SWNTls. See Refs. 74,75.

Self-focusing has not been a problem in aprotic lasers, but stimulated Brillouin and Raman scattering have been observed (Alfano et al., 1971). The thresholds for these scatterings are 35 and 100MW/cm respectively, which limits the usable flux densities in these lasers. In multimode operation, the energy converted to Raman-shifted wavelengths was reported to be <10% (Green et al., 1975). 

The composition dependence of the optical mode frequency can be calculated with the modified random-element isodisplacement (MREI) model [93-96] and similar models [97-99] or determined by measuring the Raman spectra of materials with well-defined compositions. Composition-dependence schemes can be also established from the Raman spectra of quaternary alloys like Cd ,Zn gi- yTe. The room-temperature Raman spectrum of the quaternary alloy Cdo.4Zno.3Mgo.3Te (Fig. 4) shows pairs of the LO-TO modes identified as CdTe-like, ZnTe-like, and MgTe-like modes [100]. Caused by the high degree of disorders in this system, additional features of the disorder-allowed LA and TA can be seen. The multimode behavior of this alloy can be constructed on the basis of the MREI model [100]. 

The dispersion of v and with CL has been the subject of extensive studies by several groups for the understanding of the CL heterogeneity of real samples of trans-PA [81-83]. The derivation of the distribution of CL (multimodal distributions) from the Raman line shapes as functions of the excitation wavelength has been a matter of numerous studies. Unfortunately the multimodal distributions proposed have always been... 

The resolution obtainable in laser spectroscopy experiments is limited ultimately by the bandwidth of the multimode laser output. This is not usually important in laser-induced fluorescence or Raman scattering experiments. However, for Brillouin scattering, for saturated absorption, and for two-photon absorption experiments, single-frequency lasers are essential. These are also necessary in interferometry and holography whenever the optical path difference exceeds 30 cm. Many different schemes for obtaining singlefrequency output from lasers have been reported. We shall consider only a few of the most commonly used techniques. We assume throughout that the laser has been constrained to... 

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