Coupled wave equations theory of surface-enhanced femtosecond stimulated Raman scattering

Stimulated Raman scattering (SRS) describes a family of techniques first discovered and developed in the 1960s. Whereas the nascent history of the technique is parallel to that of laser light sources, recent advances have spurred a resurgence in its use and development that has spanned across scientific fields and spatial scales. SRS is a nonlinear technique that probes the same vibrational modes of molecules that are seen in spontaneous Raman scattering. While spontaneous Raman scattering is an incoherent technique, SRS is a coherent process, and this fact provides several advantages over conventional Raman techniques, among which are much stronger signals and the ability to time-resolve the vibrational motions. Technological improvements in pulse generation and detection strategies have allowed SRS to probe increasingly smaller volumes and shorter time scales. This has enabled SRS research to move from its original domain, of probing bulk media, to imaging biological tissues and single cells at the micro scale, and, ultimately, to characterizing samples with subdiffraction resolution at the nanoscale. In this Review, we give an overview of the history of the technique, outline its basic properties, and present historical and current uses at multiple length scales to underline the utility of SRS to the molecular sciences.

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“…The exact nature of the mechanism that underpins the lineshapes in SE-SRS is currently a topic of study. 108,204–206 …”

Section: Bulk Ensembles To Single Moleculesmentioning

confidence: 99%

Stimulated Raman Scattering: From Bulk to Nano

2016

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“…In Ziegler's theory, the interference between Raman susceptibility and a stimulated surface plasmon emission results in asymmetric line shapes, and the increasing enhancement factors result in increasing dispersive line shapes [16]. In Schatz's theory, the Fano parameter depends on the ratio between the real part and the imaginary part of the square of the plasmonic field enhancement factor [17]. Different from Schatz's and Ziegler's work, our model makes an important prediction about the plasmonic enhancement factor which is given by F S | 2 F P and F P | 2 F S for PESRL and PESRG, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Ziegler et al indicated that the cross term between the heterodyned SE-FSRS signal and the plasmon light emission resulted in the dispersive-like line shape [16]. Schatz et al proposed that the asymmetric line shape resulted from the combination of two Fano contributions arising from the interference between both the real and imaginary components of the Raman local electromagnetic field and the plasmon field [17]. Both theoretical descriptions were based on reported SE-FSRS results and only discussed the SRG process.…”

Section: Introductionmentioning

confidence: 99%

Origin of dispersive line shapes in plasmon-enhanced stimulated Raman scattering microscopy

Zong

Cheng

2020

Nanophotonics

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Plasmon-enhanced stimulated Raman scattering (PESRS) microscopy has been recently developed to reach single-molecule detection limit. Unlike conventional stimulated Raman spectra, dispersive-like vibrational line shapes were observed in PESRS. Here, we propose a theoretical model together with a phasor diagram to explain the observed dispersive-like line shapes reported in our previous study. We show that the local enhanced electromagnetic field induced by the plasmonic nanostructure interferes with the molecular dipole-induced field, resulting in the dispersive profiles of PESRS. The exact shape of the profile depends on the phase difference between the plasmonic field and the molecular dipole field. We compared plasmon-enhanced stimulated Raman loss (PESRL) and plasmon-enhanced stimulated Raman gain (PESRG) signals under the same pump and Stokes laser wavelength. The PESRL and PESRG signals exhibit similar signal magnitudes, whereas their spectral line shapes show reversed dispersive profiles, which is in an excellent agreement with our theoretical prediction. Meanwhile, we verify that the nonresonant background in PESRS mainly originates from the photothermal effect. These new insights help the proper use of PESRS for nanoscale bio-imaging and ultrasensitive detection.

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“…An alternative stimulated Raman technique is SE-FSRS, which was first introduced in 2011 by Frontiera et al [142]. The SE-FSRS signals have Fano line shapes, which result from coupling between the broadband plasmonic response from colloidal nanoparticles and the narrowband vibrational coherences in the molecular adsorbates ( Figure 9D) [140,143,144]. Interestingly, the vibrational coherence's dephasing time was independent of the coupling between the plasmon and the molecule [140].…”

Section: Ultrafast Sersmentioning

confidence: 99%

Toward a mechanistic understanding of plasmon-mediated photocatalysis

et al. 2018

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One of the most exciting new developments in the plasmonic nanomaterials field is the discovery of their ability to mediate a number of photocatalytic reactions. Since the initial prediction of driving chemical reactions with plasmons in the 1980s, the field has rapidly expanded in recent years, demonstrating the ability of plasmons to drive chemical reactions, such as water splitting, ammonia generation, and CO2 reduction, among many other examples. Unfortunately, the efficiencies of these processes are currently suboptimal for practical widespread applications. The limitations in recorded outputs can be linked to the current lack of a knowledge pertaining to mechanisms of the partitioning of plasmonic energy after photoexcitation. Providing a descriptive and quantitative mechanism of the processes involved in driving plasmon-induced photochemical reactions, starting at the initial plasmon excitation, followed by hot carrier generation, energy transfer, and thermal effects, is critical for the advancement of the field as a whole. Here, we provide a mechanistic perspective on plasmonic photocatalysis by reviewing select experimental approaches. We focus on spectroscopic and electrochemical techniques that provide molecular-scale information on the processes that occur in the coupled molecular-plasmonic system after photoexcitation. To conclude, we evaluate several promising techniques for future applications in elucidating the mechanism of plasmon-mediated photocatalysis.

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Coupled wave equations theory of surface-enhanced femtosecond stimulated Raman scattering

Cited by 22 publications

References 37 publications

Stimulated Raman Scattering: From Bulk to Nano

Stimulated Raman Scattering: From Bulk to Nano

Origin of dispersive line shapes in plasmon-enhanced stimulated Raman scattering microscopy

Toward a mechanistic understanding of plasmon-mediated photocatalysis

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