We demonstrate a technique of hyperspectral imaging in stimulated Raman scattering (SRS) microscopy using a tunable optical filter, whose transmission wavelength can be varied quickly by a galvanometer mirror. Experimentally, broadband Yb fiber laser pulses are synchronized with picosecond Ti:sapphire pulses, and then spectrally filtered out by the filter. After amplification by fiber amplifiers, we obtain narrowband pulses with a spectral width of <3.3 cm(-1) and a wavelength tunability of >225 cm(-1). By using these pulses, we accomplish SRS imaging of polymer beads with spectral information. 相似文献
We investigate the role of a spatially inhomogenous nonresonant background medium on several Raman-based imaging modalities. In particular, we consider a small resonant bead submerged in a spatially heterogeneous nonresonant χ(3) background. Using detailed 3D electrodynamic simulations, we compare coherent anti-Stokes Raman scattering (CARS), frequency-modulated CARS, amplitude-modulated stimulated Raman scattering (SRS), and frequency-modulated SRS. We find that only FM-SRS is background-free. 相似文献
Abstract Launch power is limited to the milliwatt level by stimulated Brillouin scattering (SBS) in a single-channel, coherent fiber-optic network. Increasing the number of frequency-division multiplexed channels causes the power limit to decrease quickly to submilliwatt levels due to three-wave intermodulation to keep the signal-to-noise ratio from deteriorating significantly. As the number of channels increases, stimulated Raman scattering (SRS) begins to dominate. If a maximum of 0.5–dB depletion in the highest-frequency channel is allowed, SRS dominates when the number of multiplexed channels reaches about 300. Generally, the launch-power-limiting phenomenon is dependent on the number of channels being multiplexed. 相似文献
A technique of spatial coherence control, based on the synchronous amplification of a radiation in LiF crystals with F2? color centers, is demonstrated. Spatial radiation distributions of stimulated Raman scattering (SRS) in oxide crystals were investigated under picosecond laser excitation. Low spatial radiation coherence was revealed for both the transient and quasi-stationary SRS. Spatially incoherent SRS was transformed to spatially coherent radiation as a result of phase—locked picosecond synchronous laser pumping of nonlinear Raman and LiF: F2? crystals and the Stokes radiation amplification in the color center crystal. 相似文献
In this paper, we study the existence conditions of the soliton solutions induced by considering the higher-order effects
such as the third-order dispersion (TOD), self-steepening (SS), and self-frequency shift arising from stimulated Raman scattering
(SRS) simultaneously in optical soliton communication. Based on the Jacobian expansion method, we successfully obtain bright
and dark solitons. The results shows that the resultant inclusion is in agreement with Mollenauer et al. [Physical Review Letters45 (1980) 1095] when the SRS is not considered; while when the SRS is considered, the existence conditions of the higher-order
effects induced bright and dark solitons are not only quite different from those of the group velocity dispersion (GVD)-induced
and self-phase modulation (SPM)-induced solitons, but also different from those of the TOD- and SS-induced solitons discussed
by Mollenauer et al. [Physical Review Letters45 (1980) 1095]. 相似文献
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-? 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-? 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. 相似文献
Abstract: The relation between Raman scattering, resonance Raman scattering, and absorption is reviewed to determine to what extent quantitative analysis can be applied in resonance Raman spectroscopy. In addition, it is demonstrated experimentally that normal Raman spectra can be dramatically inhibited by absorption and resonance Raman effects. Raman spectra of toluene and heptane mixtures—with progressively increasing concentrations of heptane—were measured using 229-nm laser excitation. The results show that the characteristic band intensities are not directly proportional to the relative concentrations of the compounds and deviate due to absorption resonance effects. An approximated mathematical model is developed to demonstrate that the intensities of the normal Raman scattering bands are suppressed. An inhibition coefficient Ki is introduced to describe the situation and determine the penetration depth. Most remarkably, it is shown that the intensity of the resonance Raman scattering bands can be constant even when the concentration ratios differ substantially in the sampled mixtures. 相似文献
In the paper we report on picosecond-laser bulk microstructuring and stimulated Raman scattering (SRS) in type IIa single-crystal diamond in the course of multipulse irradiation at λ=532 nm wavelength using an advanced ps-laser system equipped with additional setups for on-line video imaging and photoluminescence spectra measurements. The effect of crystal orientation (relative to the incident laser beam) on (i) optical breakdown thresholds, (ii) character of bulk modifications, and (iii) generation of stimulated Raman scattering in diamond during irradiation with picosecond pulses of different durations (τ1=10 ps and τ2=44 ps) is studied. It is shown that the processes of laser-induced breakdown in the bulk of diamond (at the backside of the crystals) and bulk microstructure growth are governed by the dielectric breakdown mechanism. It is found that generation of high-order stimulated Raman scattering in diamond crystals has a considerable effect on the threshold of laser-induced breakdown and bulk microstructuring. Conditions of the efficient SRS lasing are determined, depending on the pulse duration and the direction ([100] and [110]) of the laser beam incidence. A method of local temperature measurements in the bulk of diamond based on the Stokes-to-anti-Stokes intensity ratio in the recorded SRS spectra is proposed, its applicability to determine a “pre-breakdown” temperature of diamond during multipulse ps-laser irradiation is discussed. 相似文献
Stimulated Raman scattering (SRS) microscopy is a powerful tool for chemically sensitive non-invasive optical imaging. However, ultrafast laser sources, which are currently employed, are still expensive and require substantial maintenance to provide temporal overlap and spectral tuning. SRS imaging, which utilizes continuous-wave laser sources, has a major advantage, as it eliminates the cell damage due to exposure to the high-intensity light radiation, while substantially reducing the cost and complexity of the setup. As a proof-of-principle, we demonstrate microscopic imaging of dimethyl sulfoxide using two independent, commonly used lasers, a diode-pumped, intracavity doubled 532-nm laser and a He–Ne laser operating at 632.8-nm. 相似文献
Nonlinear optical microscopy (NLOM) relies on nonlinear light–matter interactions to provide images from larger depths within biological structures compared to conventional confocal fluorescence microscopy. These nonlinear light–matter interactions include multiphoton excitation fluorescence (MPEF), second‐harmonic generation (SHG), coherent anti‐Stokes Raman scattering (CARS), and stimulated Raman scattering (SRS). This review discusses the theories of and instrumentation for various NLOM techniques, with a particular focus on endogenous signals and exogenous probes. These signals and probes expand the breadth of information that optical imaging can provide. We also discuss the application of NLOM in biomedical research, including tissue engineering, drug delivery and clinical diagnostics. Current technological limitations are also discussed.
We demonstrate stimulated supercontinuum-radiation of carbon disulfide (CS2) influenced by biological molecules all-trans-β -carotene in liquid core optical fibre (LCOF). By virtue of the broad fluorescence characteristics and large third-order optical nonlinearities of all-{trans}-β-carotene,the high-order Stokes lines of stimulated Raman scattering (SRS) and the multi-order Stokes lines of stimulated Brillouin scattering (SBS) excitated by SRS are observed at low input-laser energies. The results indicate that the fluorescence not only enhances the SRS, but also the SBS. These Stokes lines generate the SRS--SBS supercontinuum radiation (RBSR). A flat-amplitude bandwidth of 110 nm from 515nm to 625nm is observed when a frequency-doubled Nd:YAG laser at 532nm with an energy of 0.86mJ is used. This result is expected to be useful for the multi-wavelength fibre laser. 相似文献
We describe the principle and experiment of stimulated Raman scattering (SRS) microscopy, which has various advantages such
as high-contrast and high sensitivity. To discuss how these advantages are realized in SRS microscopy, we introduce an intuitive
picture of SRS, where the SRS process is viewed as homodyne detection of a nonlinear-optical signal by the excitation pulse. 相似文献
Stimulated Raman scattering (SRS) spectra in several mixed liquids with a large optical Kerr constant are studied with nanosecond and picosecond light pulses. These spectra show a dependence of the SRS intensity on the relaxation times T2 of Raman active modes. 相似文献
In this study we report the first observation of spontaneous Raman solitons in stimulated Raman scattering (SRS) by the gas NH3. The scattered radiation is called Stokes radiation. Raman solitons are of considerable interest, because their existence can be explained by quantum-mechanical fluctuations of the electromagnetic field in vacuum. We have observed spontaneous Raman solitons in a forward SRS configuration for two different molecular transitions of NH3, the laser emissions at 58 μm and 72.6 μm wavelength. These are optically pumped by 10 μm CO2-laser pulses with a duration of 100 ns and an energy of 150 mJ. Spontaneous Raman solitons are short spikes in the pump pulse which occur during its depletion. Their origin is the rapid π phase change of the Stokes seed. In contrast to other laboratories we have used single-pass cells. Thus, we have succeeded in observing multiple spontaneous Raman solitons during one pump pulse. Previous experiments with multi-pass cells never showed multiple solitons. Since multiple spontaneous Raman solitons have already been reported in an earlier experiment with a single-pass cell filled with hydrogen at high pressure, we conclude that such multiple Raman solitons can be observed mainly in this type of gas cell. Subsequently, we have performed statistical measurements on the delay time and the height of the spontaneous Raman solitons in the depleted pump pulse for the 58 μm-NH3 emission. We have compared these statistics with theory and equivalent experimental results of other laboratories. They are in good agreement with the assumption that quantum-mechanical fluctuations are the origin of spontaneous Raman solitons. The most recent theories postulate that the origin of the formation of spontaneous Raman solitons can be explained by the rapid π phase change of the Stokes seed as well as that of the laser or polarization wave. Therefore, we have determined the phase of the spontaneous Raman solitons relative to the depleted pump pulse. Although, such changes of sign of the relative phase have already been observed in an earlier SRS experiment with hydrogen at high pressure, we did not detect any in our experiment. Therefore, we conclude that in this experiment the π phase change occurs in the Stokes or polarization wave. 相似文献
The discovery of a novel phase‐locked frequency comb generated from a monolithic laser with the concurrent processes of self‐mode locking (SML) and stimulated Raman scattering (SRS) is reported. It is experimentally shown that the width of the Raman gain can be exploited to considerably expand the frequency comb of a monolithic SML crystal laser via the SRS process. At a pump power of 6.5 W, an output power of 140 mW in the Stokes wave with a pulse width as narrow as 2.9 ps at a pulse repetition rate of 6.615 GHz is obtained. The present finding not only provides useful insights into the monolithic intracavity SRS process but also paves the way for generating mode‐locked pulses based on monolithic self‐Raman crystals. 相似文献