Raman-enhanced Nondegenerate Four-wave Mixing Research Articles

Analysis of Raman-enhanced nondegenerate four-wave mixing with factorized time correlator diagrams

The work of Fu et al. regarding temporal signal behavior in noisy light-induced, Raman-enhanced, nondegenerate four-wave mixing (I(2)RENFWM) is reassessed using factorized time correlation (FTC) analysis. Close correspondence is observed between the FTC predictions and the prior analysis. Strikingly, the observed experimental and theoretical behavior of the I(2)RENFWM signal is largely captured by a single FTC diagram, from which physical insight can be obtained.

Phase-Sensitive Detection of Raman-Enhanced NondegenerateFour-Wave Mixing by Polarization Interference

We demonstrated a phase-sensitive method for studying the Raman-enhancednondegenerate four-wave mixing (RENFWM). The reference beam is another four-wavemixing signal, which propagates along the same optical path as the RENFWM signal.This method is used for studying the phase dispersion of the third-ordersusceptibility χ(3) and for the optical heterodyne detection of the RENFWMsignal. PACS: 42. 65. Hw

Phase-sensitive detection of Raman-enhanced nondegenerate four-wave mixing

Based on the polarization interference between two four-wave mixing (FWM) processes, we demonstrate a phase-sensitive method for studying Raman-enhanced nondegenerate four-wave mixing (RENFWM). The reference beam is another FWM signal, which propagates along the same optical path as the RENFWM signal. We have employed this method to study the phase dispersion of the third-order susceptibility χ(3) and for optical heterodyne detection of the RENFWM signal.

Phase fluctuations on Raman-enhanced nondegenerate four-wave mixing

We have employed phase-diffusion model to study the effects of laser field correlation on the Raman-enhanced nondegenerate four-wave mixing (RENFWM). The different roles of the field fluctuations have been pointed out. A time-delayed method has been proposed to suppress the thermal background. An enhancement of the ratio between the resonant and nonresonant RENFWM signal intensities was found as the time delay is increased when the laser has broadband linewidth. When the lasers have Gaussian line shape, we also present a second-order coherence function theory to elucidate the temporal asymmetry behavior of the RENFWM.

Effects of Field-Correlation on Raman-Enhanced Nondegenerate Four-Wave Mixing Spectra

The effects of field correlation on Raman-enhanced nondegenerate four-wave mixing (RENFWM) have been investigated by examining the RENFWM spectra as a function of time delay between two beams. An enhancement of the ratio between the resonant and nonresonant RENFWM signal intensities was found as the time delay was increased when the laser had broadband linewidth.

Field-correlation effects on Raman-enhanced nondegenerate four-wave mixing

The effects of field correlation on Raman-enhanced nondegenerate four-wave mixing (RENFWM) have been investigated by examining the RENFWM spectra as a function of time delay between two beams. We present a theory in which the underlying physics is emphasized. The field correlation has little influence on the RENFWM spectra when the laser has narrow bandwidth. In contrast, the ratio between the resonant and nonresonant RENFWM signal intensities increases as time delay is increased when the laser has broadband linewidth. Experiments with ${\mathrm{CS}}_{2}$ as sample have been performed to demonstrate the field-correlation effects on the RENFWM spectra.

Time-delayed Raman-enhanced nondegenerate four-wave mixing with a broadband laser source.

We report an experiment of the time-delayed Raman-enhanced nondegenerate four-wave mixing (RENFWM) with a broadband laser in carbon disulfide (${\mathrm{CS}}_{2}$). We studied the RENFWM signal intensity as a function of the relative time delay \ensuremath{\tau} between two beams which originate from a single broadband laser source. Our results indicate that the temporal behavior of the RENFWM is asymmetric with the maximum of the signal shifted from \ensuremath{\tau}=0. Furthermore, unlike the corresponding coherent Stokes Raman scattering (CSRS) no coherent spike appears at \ensuremath{\tau}=0. From our experimental results the relaxation time of the Raman mode can be extracted directly. We present a second-order coherence function theory to elucidate the physics of the basic features of the time-delayed RENFWM. We also discuss the difference between the RENFWM and the CSRS from a physical viewpoint.

Time-Delayed Raman-Enhanced Nondegenerate Four-Wave-Mixing Experiments with Incoherence Light in Carbon Disulfide

We report for the first time an experiment of the time-delayed Raman-enhanced non-degenerate four-wave-mixing (RENFWM) with incoherence light in carbon disulfide. We studied the RENFWM signal intensity as a function of the relative time delay τ between two beams which originate from a single broadband laser source. Our results indicate that the temporal behavior of the RENFWM is asymmetric with the maximum of the signal shifted from τ = 0. From our experimental results the relaxation time of the Raman mode can be extracted directly.

Theoretical study of the suppression of thermal background in the Raman-enhanced nondegenerate four-wave-mixing spectrum by a time-delayed method.

We have studied theoretically the dependence of the Raman-enhanced nondegenerate four-wave-mixing (RENFWM) spectrum on the relative time delay between two pump beams-tau when a thermal effect exists in the sample. Using the chaotic model for the incident laser beams, we give the conditions that the thermal background can be eliminated completely when the relative time delay is much longer than the laser coherence time. In this limit, the theoretical RENFWM spectra show the normal asymmetry due to the interference between the Raman-resonant term and the nonresonant background originating solely from the molecular-reorientational grating. We then turn our attention to the dependence of the RENFWM signal intensity on the relative time delay when the laser frequencies are fixed. Our results indicate that RENFWM is asymmetric about tau = 0 and the maximum of the RENFWM signal does not occur at tau = 0. When the beating frequency between the pump beam and the probe beam is off resonant from the Raman mode, the RENFWM signal exhibits damping oscillation as the time delay increases. We also show that the temporal behavior of the RENFWM signal is drastically different if the laser sources are described by a phase-diffusion model. The different roles of the phase fluctuation and the amplitude fluctuation can be understood in the time domain.

Raman-enhanced nondegenerate four-wave mixing

It is well known that resonant four-wave mixing can be used for high-resolution laser spectroscopy. Here we report an extensive study of Raman- enhanced nondegenerate four-wave mixing (RENFWM) in benzene. Instead of using a broadband laser source and single-shot measurement, as in the first experiment by Saha and Hellwarth,1 we measured the spectrum by scanning the wavelength of a narrowband dye laser used as the probe beam. Our results demonstrate the feasibility of using RENFWM as a practical and powerful tool for coherent Raman spectroscopy.

THE TRANSVERSE RELAXATION TIME MEASUREMENT FOR RAMAN MODE BY NONDEGENERATE FOUR WAVE MIXING

The transverse relaxation time measurement for Raman mode by Raman enhanced nonde-generate four wave mixing (RENFWM) has been made in the frequency domain. We get spectra of RENFWM that the nonresonant background is suppressed. The transverse relaxation time of Raman mode in benzene and methlybenzene is obtained as 1.5 ps and 2 ps respectively.