Some new aspects in stimulated raman scattering from hydrogen gas.
Stimulated Raman scattering from hydrogen gas, discussing simultaneous SRS of harmonic ruby radiation and vibrational rotational lines
Duardo, J. A.↗
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Surface-enhanced stimulated Raman spectroscopy with squeezed photonic states
Recent advances in generating light in specific quantum states facilitate new sensing applications and enhance or revitalize established measurement and sensing techniques. Stimulated Raman spectroscopy (SRS), a measurement modality based on Raman scattering, could benefit from tuning the quantum properties of the pump and the Stokes lights or the properties of quantum states of the stimulating and excitation fields. Additionally, this modality could also benefit from field enhancement accompanied by plasmon excitation in the surface regions of metal nanoparticles. We present a theoretical investigation of stimulated Raman scattering involving squeezed states of light. The concept of surface- and quantum-enhanced stimulated Raman scattering is introduced. Furthermore, expressions for the respective SRS transition rates are derived, and their dependence on the quantum states of the optical field is discussed, with particular emphasis on the squeezing parameters characterizing these states. For cases involving surface enhancements, we also employ classical computational electrodynamics to guide our exploration of atomically large systems that support plasmon excitation.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Analysis of the stimulated Raman effects in an anisotropic crystal KDP.
Stimulated Raman effects in anisotropic crystal potassium dihydrogen phosphate with Stokes generations
ANISOTROPIC MATERIAL↗
Squeezed Light Stimulated Raman Scattering (SRS) Microscopy for Bioenergy Applications
Stimulated Raman scattering (SRS) microscopy using picosecond near-IR pulses have provided a great penetration depth with reduced fluorescence interference when imaging biological samples for bioenergy applications. These tools have provided insight into 1) tracking the degradation of chemical composites in biomass feedstocks to investigate the recalcitrant factors during the deconstruction processes, 2) monitoring the production of chemicals in photosynthetic plants and wood-digesting microorganisms, and 3) probing plant-bacteria interactions. However, the above processes are usually slow and require continuous imaging for an extended period. This is challenging for classic SRS because the laser power needed to achieve enough sensitivity causes photodamage in the samples during such long experiments. Quantum-squeezed light with reduced noise in the intensity quadrature can improve the sensitivity of classic SRS microscopy beyond the shot noise limit. The successful squeezing of one of the picosecond pulses in the above SRS will improve sensitivity and reduce photodamage, greatly expanding the range of studies available to SRS microscopy.
BIOMASS FUELS↗
Optical Stark effect in the four-wave mixing and stimulated Raman spectra of N2
The influence of the optical Stark effect on spectral line shapes in four-wave-mixing Raman spectroscopy (FWMRS) and stimulated Raman spectroscopy (SRS) is investigated experimentally and theoretically. Using an experimental setup capable of rapid alternation between the simultaneous measurement of coherent Stokes Raman spectroscopy and inverse Raman spectroscopy at low and high intensities, together with a sophisticated frequency reference scheme, it was possible to perform a rather direct comparison between Stark-broadened and non-Stark-broadened spectra of both classes of Raman spectroscopies. The results demonstrate that SRS spectra show more Stark shift and broadening than their FWMRS counterparts. A discrepancy with theoretical results is pointed out, and an attempt is made to explain it.
Moosmuller, H.↗
A study of transient stimulated Raman scattering and self-focusing in the picosecond time regime
Two third order processes, stimulated Raman scattering and self-focusing, with picosecond pulses are studied. In the case of transient stimulated scattering, the gain is reduced from the steady state value, and qualitatively new features, such as shortening and delay of the Stokes pulse relative to the laser pulse, appear. These predictions are extended to realistic laser pulses, and experiments confirm all of the theoretical predictions. The self-focusing and frequency broadening of picosecond pulses is studied in the absence of stimulated Raman scattering in several materials with large orientational Kerr constants. Measurements of the relaxation time indicate that the orientational Kerr effect is important in the self-focusing of picosecond pulses. Self-focused filaments are observed to propagate with constant diameters over a distance greater than 10 cm, but disappear before the end of a 20 cm cell. The filaments radiate light continuously along their path and the spectrum of the light shows that the frequency content extends symmetrically for several hundred wave numbers on either side of the laser frequency.
Reintjes, J. F.↗
Stimulated Raman emission in liquids.
Angular emission properties of stimulated Raman radiation from liquids, noting two classes of radiation
RAMAN SCATTERING↗
Development and applications of tunable, narrow band lasers and stimulated Raman scattering devices for atmospheric lidar
The main thrust of the program was the study of stimulated Raman processes for application to atmospheric lidar measurements. This has involved the development of tunable lasers, the detailed study of stimulated Raman scattering, and the use of the Raman-shifted light for new measurements of molecular line strengths and line widths. The principal spectral region explored in this work was the visible and near-IR wavelengths between 500 nm and 1.5 microns. Recent alexandrite ring laser experiments are reported. The experiments involved diode injection-locking, Raman shifting, and frequency-doubling. The experiments succeeded in producing tunable light at 577 and 937 nm with line widths in the range 80-160 MHz.
Wilkerson, Thomas D.↗
Stimulated Raman shifting of the Nd:YAG fourth harmonic (266 nm) in H2, HD, and D2
The dependence of the first Stokes stimulated Raman conversion efficiency of fourth-harmonic radiation from a Nd:YAG laser at 266 nm has been studied for the isotopic species H2, HD, and D2 as a function of gas pressure and laser energy using a low numerical aperture (about 0.0045) pumping geometry. While the laser energy threshold for first Stokes conversion varies significantly among the species, photon conversion efficiencies of at least 50 percent can be achieved for all of them for laser pump energies at 266 nm of 50 mJ/pulse or less. This study provides a new measurement of the differential cross section for stimulated Raman scattering in HD of 8.1 + or - 2.4 x 10 to the -29th sq cm/sr at 266 nm and at high pressures, and agreement is found with previous measurements of the cross sections for H2 and D2. The results have been used to optimize the laser transmitter system for a differential-absorption lidar to measure tropospheric ozone concentration profiles.
Haner, David A.↗
Stimulated Raman Scattering Microscopy: Real-Time In-Situ Physical and Chemical Characterization of Reverse Osmosis Desalination Membrane Scaling
We introduce a stimulated Raman scattering (SRS) methodology designed for rapid, real-time, and in situ monitoring of RO membrane scaling adapted for bench-scale desalination flow cells. The methodology can provide new insights into membrane scaling dynamics by offering time-resolved reflection imaging of inorganic crystal growth, coupled with chemical identification from Raman spectral data. These capabilities allow for direct local measurement of the membrane surface area covered by different scalants as well as an approximation of the scalant volume using three-dimensional, integrated Raman intensity. The 2D and 3D SRS results obtained from CaSO 4 scaling experiments are compared to and are in reasonable agreement with those provided by confocal microscopy. The real-time physical and chemical characterization capabilities presented here could be extended to study combinations of inorganic, organic, and biological fouling. Overall, the SRS methodology represents an advancement in real-time sensing of membrane fouling that offers the potential for improved operation, lower cost, and more resilient RO membrane systems for sustainable water management.
42 ENGINEERING↗
Ultrashort pulse formation in a short-pulse- stimulated Raman oscillator
Ultrashort pulse formation in short pulse stimulated Raman oscillator, achieving partial group velocity matching
Colles, M. J.↗
Reassessment of the theory of stimulated Raman scattering
A modification of the standard theory of stimulated Raman scattering (SRS) first proposed by Sparks (1974, 1975) is analyzed and shown to incorporate a possibly important physical effect; however, its original formulation is incorrect. The analysis is based on an exact numerical integration of the coupled equations of the modified theory, the results of which are compared with both the conventional theory of SRS and with one set of experimental data. A reformulation of the modified theory is suggested that leads to a gain which is in somewhat better agreement with the data than is the conventional theory.
Fralick, G. C.↗
Modeling of transverse stimulated Raman scattering in KDP/DKDP in large-aperture plates suitable for polarization control
Transverse stimulated Raman scattering (TSRS) in potassium dihydrogen phosphate (KDP) and deuterated potassium dihydrogen phosphate (DKDP) plates for large-aperture, inertial confinement fusion (ICF)-class laser systems is a well-recognized limitation giving rise to parasitic energy conversion and laser-induced damage. The onset of TSRS is manifested in plates exposed to the ultraviolet section of the beam. TSRS amplification is a coherent process that grows exponentially and is distributed nonuniformly in the crystal and at the crystal surfaces. To understand the growth and spatial distribution of TSRS energy in various configurations, a modeling approach has been developed to simulate the operational conditions relevant to ICF-class laser systems. Specific aspects explored in this work include (i) the behavior of TSRS in large-aperture crystal plates suitable for third-harmonic generation and use as wave plates for polarization control in current-generation ICF-class laser system configurations; (ii) methods, and their limitations, of TSRS suppression and (iii) optimal geometries to guide future designs.
47 OTHER INSTRUMENTATION↗
Measuring molecular flows with high-resolution stimulated Raman spectroscopy
It is proposed to use high-resolution stimulated Raman spectroscopy to directly measure high-speed molecular flow velocities in wind tunnels and in combustive chambers. A feasibility study indicates that flow speeds from Mach 0.04 up may be measured with the proposed method using available laser systems. It is pointed out that the success of the proposed technique will make it possible to measure all interesting flow parameters, i.e., species concentration, temperature, and velocity, in a time of less than 1 microsecond at a repetition rate of 10,000/s using a single experimental arrangement.
She, C. Y.↗
Stimulated Raman scattering in an infrared active, nontotally symmetric vibration of alpha-quartz.
Stimulated Raman scattering in IR active nontotally symmetric vibration of alpha quartz crystal, noting parametric oscillation
RAMAN SCATTERING↗
Observation and measurement of molecular flow using stimulated Raman gain spectroscopy
The observation and measurement of frequency shifts in stimulated Raman gain spectroscopy resulting from subsonic molecular nitrogen flows emerging from a simple nozzle are reported. The flow velocity in the region of the measurement was determined to be 145 m/s with an accuracy of plus or minus 30 m/s. It is expected that significantly better flow-velocity resolution will be obtained in future experiments using inverse Raman scattering.
Herring, G. C.↗
Mastering Femtosecond Stimulated Raman Spectroscopy: A Practical Guide
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Stimulated Raman scattering and the extreme high-velocity H2O maser features in W49
Stimulated Raman scattering of the intense 22.2-GHz water-vapor maser radiation within W49 is examined as a possible explanation of the extremely broad spectrum of W49 extending to + or - 200 km/sec apparent Doppler velocity. Under the most favorable conditions, Raman scattering from ammonia molecules is calculated to be observable. It is unlikely that the Raman process contributes appreciably in the case of W49, as it fails to predict the observed spatial and spectral distribution of the radiation.
Boyd, R. W.↗