Marangoni, M. et al. Synthesis of picosecond pulses by spectral compression and shaping of femtosecond pulses in engineered quadratic nonlinear media. Opt. Lett. 34, 241–243 (2009).

Ellis, S. R., Hoffman, D. P., Park, M. & Mathies, R. A. Difference bands in time-resolved femtosecond stimulated Raman spectra of photoexcited intermolecular electron transfer from chloronaphthalene to tetracyanoethylene. J. Phys. Chem. A 122, 3594–3605 (2018).

The optical fibers used in fiber optics are sometimes made of plastic but most often are made of glass. A typical glass optical fiber has a diameter of 125 micrometers (μm) or 0.125 mm (0.005 inches). Plastic fibers are made of polymethylmethacrylate, polystyrene, or polycarbonate. These are cheaper to produce and more flexible than glass fibers, but their attenuation of light restricts their use to shorter links.

Savitzky, A. & Golay, M. J. E. Smoothing and differentiation of data by simplified least squares procedures. Anal. Chem. 36, 1627 (1964).

Kruglik, S. G. et al. Subpicosecond oxygen trapping in the heme pocket of the oxygen sensor FixL observed by time-resolved resonance Raman spectroscopy. Proc. Natl Acad. Sci. USA 104, 7408–7413 (2007).

Frostig, H., Katz, O., Natan, A. & Silberberg, Y. Single-pulse stimulated Raman scattering spectroscopy. Opt. Lett. 36, 1248 (2011).

McCamant, D. W., Kukura, P. & Mathies, R. A. Femtosecond stimulated Raman study of excited-state evolution in bacteriorhodopsin. J. Phys. Chem. B 109, 10449–10457 (2005).

Sandoval, J. S. & McCamant, D. W. The best models of Bodipy’s electronic excited state: comparing predictions from various DFT functionals with measurements from femtosecond stimulated Raman spectroscopy. J. Phys. Chem. A 127, 8238–8251 (2023).

Tauber, M. J., Mathies, R. A., Chen, X. & Bradforth, S. E. Flowing liquid sample jet for resonance Raman and ultrafast optical spectroscopy. Rev. Sci. Instrum. 74, 4958–4960 (2003).

Wang, Z., Jiang, J., Huang, Y. & Liu, W. Tracking twisted intramolecular charge transfer and isomerization dynamics in 9-(2,2-dicyanovinyl) julolidine using femtosecond stimulated Raman spectroscopy. Chin. J. Chem. Phys. 36, 397–403 (2023).

Fiber optics telecommunication uses infrared light in the wavelength ranges of 0.8–0.9 μm or 1.3–1.6 μm - wavelengths, efficiently generated by light-emitting diodes or semiconductor lasers and that suffer minimum attenuation in glass fibers.

Chen, C. et al. Structural characterization of fluorescent proteins using tunable femtosecond stimulated Raman spectroscopy. Int. J. Mol. Sci. 24, 11991 (2023).

Zhu, L., Liu, W. & Fang, C. A versatile femtosecond stimulated Raman spectroscopy setup with tunable pulses in the visible to near infrared. Appl. Phys. Lett. 105, 041106 (2014).

Kuramochi, H., Takeuchi, S. & Tahara, T. Femtosecond time-resolved impulsive stimulated Raman spectroscopy using sub-7-fs pulses: apparatus and applications. Rev. Sci. Instrum. 87, 43107 (2016).

Lafuente, B., Downs, R. T., Yang, H. & Stone, N. in Highlights in Mineralogical Crystallography (eds Armbruster, T. & Danisi, R. M.) (De Gruyter, 2015).

Bera, K., Douglas, C. J. & Frontiera, R. R. Femtosecond Raman microscopy reveals structural dynamics leading to triplet separation in rubrene singlet fission. J. Phys. Chem. Lett. 8, 5929–5934 (2017).

Yoshizawa, M. & Kurosawa, M. Femtosecond time-resolved Raman spectroscopy using stimulated Raman scattering. Phys. Rev. A 61, 013808 (1999).

Batignani, G. et al. Temperature dependence of Coherent versus spontaneous Raman Scattering. Preprint at https://arxiv.org/abs/2405.00521 (2024).

Batignani, G. et al. Visualizing excited-state dynamics of a diaryl thiophene: femtosecond stimulated Raman scattering as a probe of conjugated molecules. J. Phys. Chem. Lett. 7, 2981–2988 (2016).

Amplification of a desired, weak, optical signal (ES) by its mixing with a strong field (EL), leading to the measured intensity \(I={{\rm{| }}{E}_{{\rm{L}}}{\rm{| }}}^{2}+{{\rm{| }}{E}_{{\rm{S}}}{\rm{| }}}^{2}+{E}_{{\rm{L}}}{E}_{{\rm{S}}}^{* }+{E}_{{\rm{S}}}{E}_{{\rm{L}}}^{* }\).

Frostig, H., Bayer, T., Dudovich, N., Eldar, Y. C. & Silberberg, Y. Single-beam spectrally controlled two-dimensional Raman spectroscopy. Nat. Photon. 9, 339–343 (2015).

Kovalenko, S. A., Dobryakov, A. L. & Ernsting, N. P. An efficient setup for femtosecond stimulated Raman spectroscopy. Rev. Sci. Instrum. 82, 063102 (2011).

Gebrekidan, M. T., Knipfer, C. & Braeuer, A. S. Refinement of spectra using a deep neural network: fully automated removal of noise and background. J. Raman Spectrosc. 52, 723–736 (2021).

Ruchira Silva, W. & Frontiera, R. R. Excited state structural evolution during charge-transfer reactions in betaine-30. Phys. Chem. Chem. Phys. 18, 20290–20297 (2016).

Batignani, G., Mai, E., Fumero, G., Mukamel, S. & Scopigno, T. Absolute excited state molecular geometries revealed by resonance Raman signals. Nat. Commun. 13, 7770 (2022).

Fumero, G. et al. Two-dimensional impulsively stimulated resonant Raman spectroscopy of molecular excited states. Phys. Rev. X 10, 11051 (2020).

Würthwein, T., Lüpken, N. M., Irwin, N. & Fallnich, C. Mitigating cross-phase modulation artifacts in femtosecond stimulated Raman scattering. J. Raman Spectrosc. 51, 2265–2271 (2020).

McCamant, D. W., Kukura, P., Yoon, S. & Mathies, R. A. Femtosecond broadband stimulated Raman spectroscopy: apparatus and methods. Rev. Sci. Instrum. 75, 4971–4980 (2004). This article presents a pioneering description of a basic FSRS setup.

Pastorczak, M., Nejbauer, M. & Radzewicz, C. Femtosecond infrared pump-stimulated Raman probe spectroscopy: the first application of the method to studies of vibrational relaxation pathways in the liquid HDO/D2O system. Phys. Chem. Chem. Phys. 21, 16895–16904 (2019). This article describes the use of FSRS with an infrared actinic pump.

Ferrante, C. et al. Ultrafast dynamics and vibrational relaxation in six-coordinate heme proteins revealed by femtosecond stimulated Raman spectroscopy. J. Am. Chem. Soc. 142, 2285–2292 (2020).

Chergui, M., Beye, M., Mukamel, S., Svetina, C. & Masciovecchio, C. Progress and prospects in nonlinear extreme-ultraviolet and X-ray optics and spectroscopy. Nat. Rev. Phys. 5, 578–596 (2023).

Czerwinski, L., Nixdorf, J., Di Florio, G. & Gilch, P. Broadband stimulated Raman microscopy with 01 ms pixel acquisition time. Opt. Lett. 41, 3021–3024 (2016).

Hontani, Y. et al. Molecular origin of photoprotection in cyanobacteria probed by watermarked femtosecond stimulated Raman spectroscopy. J. Phys. Chem. Lett. 9, 1788–1792 (2018).

Marangoni, M. A. et al. Narrow-bandwidth picosecond pulses by spectral compression of femtosecond pulses in second-order nonlinear crystals. Opt. Express 15, 8884 (2007).

Through the principle of total internal reflection, light rays beamed into the optical fibers can propagate within the core for great distances with exceptionally concise attenuation or reduction in intensity, making fiber optics the ideal method for transmitting data over long distances.

Pontecorvo, E. et al. Femtosecond stimulated Raman spectrometer in the 320–520 nm range. Opt. Express 19, 1107–1112 (2011). To our knowledge, this article is the first demonstration of a tunable Raman pump FSRS with a second harmonic generation spectral compression approach.

The stimulated Raman scattering time-domain analogue, in which a full scan of the temporal delay between two ultrashort pulses is required to record a single Raman spectrum in the time domain. The addition of an actinic pump turns impulsive stimulated Raman into a time-resolved technique capable of probing excited-state dynamics, similarly to femtosecond stimulated Raman scattering.

Zong, C. & Cheng, J. X. Origin of dispersive line shapes in plasmon-enhanced stimulated Raman scattering microscopy. Nanophotonics 10, 617–625 (2020).

Introduction (T.S., G.B., C.F., G.F. and M.M.); Experimentation (T.S., G.B., C.F., G.F. and M.M.); Results (T.S., G.B., C.F., G.F. and M.M.); Applications (T.S., G.B., C.F., G.F. and M.M.); Reproducibility and data deposition (T.S., G.B., C.F., G.F. and M.M.); Limitations and optimizations (T.S., G.B., C.F., G.F. and M.M.); Outlook (T.S., G.B., C.F., G.F. and M.M.); overview of the Primer (T.S.).

Pu, R. et al. Investigation of ultrafast configurational photoisomerization of bilirubin using femtosecond stimulated Raman spectroscopy. J. Phys. Chem. Lett. 14, 809–816 (2023).

Zhou, J., Yu, W. & Bragg, A. E. Structural relaxation of photoexcited quaterthiophenes probed with vibrational specificity. J. Phys. Chem. Lett. 6, 3496–3502 (2015).

Bell, I. M., Clark, R. J. H. & Gibbs, P. J. Raman Spectroscopic Library of Natural and Synthetic Pigments. Christopher Ingold Laboratories/University College London https://www.chem.ucl.ac.uk/resources/raman/ (1998).

A signal in which various frequencies arrive at different time delays. In optical pulses, chirp commonly stems from the chromatic dispersion caused by transmitting optics, leading to red-shifted spectral components arriving earlier (positive chirp) or later (negative chirp) than the blue-shifted ones.

Jen, M., Lee, S., Lee, G., Lee, D. & Pang, Y. Intramolecular charge transfer of curcumin and solvation dynamics of DMSO probed by time-resolved Raman spectroscopy. Int. J. Mol. Sci. 23, 1727 (2022).

Hart, S. M., Silva, W. R. & Frontiera, R. R. Femtosecond stimulated Raman evidence for charge-transfer character in pentacene singlet fission. Chem. Sci. 9, 1242–1250 (2018).

Weigel, A. et al. Femtosecond stimulated Raman spectroscopy of flavin after optical excitation. J. Phys. Chem. B 115, 3656–3680 (2011).

Lynch, P. G., Das, A., Alam, S., Rich, C. C. & Frontiera, R. R. Mastering femtosecond stimulated Raman spectroscopy: a practical guide. ACS Phys. Chem. Au 4, 1–18 (2024).

Chen, C. et al. Unveiling structural motions of a highly fluorescent superphotoacid by locking and fluorinating the GFP chromophore in solution. J. Phys. Chem. Lett. 8, 5921–5928 (2017).

Zhang, W. et al. Direct tracking excited-state intramolecular charge redistribution of acceptor–donor–acceptor molecule by means of femtosecond stimulated Raman spectroscopy. J. Phys. Chem. B 125, 4456–4464 (2021).

Kuramochi, H., Fujisawa, T., Takeuchi, S. & Tahara, T. Broadband stimulated Raman spectroscopy in the deep ultraviolet region. Chem. Phys. Lett. 683, 543–546 (2017). This article describes FSRS with a tunable ultraviolet pump.

Pižl, M. et al. Time-resolved femtosecond stimulated Raman spectra and DFT anharmonic vibrational analysis of an electronically excited rhenium photosensitizer. J. Phys. Chem. A 124, 1253–1265 (2020).

Nature Reviews Methods Primers thanks Chong Fang, David McCamant and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

When glass fibers of core/cladding design were introduced in the early 1950s, the presence of impurities restricted their employment to the short lengths sufficient for endoscopy. In 1966, electrical engineers Charles Kao and George Hockham, working in England, suggested using fibers for telecommunication, and within two decades silica glass fibers were being produced with sufficient purity that infrared light signals could travel through them for 100 km (60 miles) or more without having to be boosted by repeaters. In 2009 Kao was awarded the Nobel Prize in Physics for his work. Plastic fibers, usually made of polymethylmethacrylate, polystyrene, or polycarbonate, are cheaper to produce and more flexible than glass fibers, but their greater attenuation of light restricts their use to much shorter links within buildings or automobiles.

Mehlenbacher, R. D., Lyons, B., Wilson, K. C., Du, Y. & McCamant, D. W. Theoretical analysis of anharmonic coupling and cascading Raman signals observed with femtosecond stimulated Raman spectroscopy. J. Chem. Phys. 131, 244512 (2009).

Harbola, U., Umapathy, S. & Mukamel, S. Loss and gain signals in broadband stimulated-Raman spectra: theoretical analysis. Phys. Rev. A 88, 11801 (2013).

Anderson, K. E. H., Sewall, S. L., Cooney, R. R. & Kambhampati, P. Noise analysis and noise reduction methods in kilohertz pump–probe experiments. Rev. Sci. Instrum. 78, 073101 (2007).

Yoon, S., Kukura, P., Stuart, C. M. & Mathies, R. A. Direct observation of the ultrafast intersystem crossing in tris(2,2′-bipyridine)ruthenium(II) using femtosecond stimulated Raman spectroscopy. Mol. Phys. 104, 1275–1282 (2006).

In telecommunications, optical fibers have been used to replace copper wire in long-distance telephone lines and for linking computers within local area networks. Fiber optics is also the basis of the fiberscopes used for endoscopy or inspecting the interiors of manufactured structural products.

Kukura, P., McCamant, D. W., Yoon, S., Wandschneider, D. B. & Mathies, R. A. Structural observation of the primary isomerization in vision with femtosecond-stimulated Raman. Science 310, 1006–1009 (2005).

Ultrafastspectroscopyppt

Dantus, M. & Lozovoy, V. V. Experimental coherent laser control of physicochemical processes. Chem. Rev. 104, 1813–1860 (2004).

Fang, C., Frontiera, R. R., Tran, R. & Mathies, R. A. Mapping GFP structure evolution during proton transfer with femtosecond Raman spectroscopy. Nature 462, 200–204 (2009). To our knowledge, this article presents the first FSRS application to track nuclear motion underlying proton transfer.

Kuramochi, H., Takeuchi, S., Kamikubo, H., Kataoka, M. & Tahara, T. Skeletal structure of the chromophore of photoactive yellow protein in the excited state investigated by ultraviolet femtosecond stimulated Raman spectroscopy. J. Phys. Chem. B 125, 6154–6161 (2021).

Sciortino, G. et al. Four-channel differential lock-in amplifiers with autobalancing network for stimulated Raman spectroscopy. IEEE J. Solid State Circuits 56, 1859–1870 (2021).

Agrawal, G. P., Baldeck, P. L. & Alfano, R. R. Temporal and spectral effects of cross-phase modulation on copropagating ultrashort pulses in optical fibers. Phys. Rev. A 40, 5063–5072 (1989).

Wang, Z. et al. Mapping the complete photocycle that powers a large Stokes shift red fluorescent protein. Angew. Chem. Int. Ed. 62, e202212209 (2023).

Han, X. X., Rodriguez, R. S., Haynes, C. L., Ozaki, Y. & Zhao, B. Surface-enhanced Raman spectroscopy. Nat. Rev. Methods Primers 1, 87 (2022).

Virtanen, P. et al. SciPy 1.0: fundamental algorithms for scientific computing in Python. Nat. Methods 17, 261–272 (2020).

Kukura, P., McCamant, D. W., Davis, P. H. & Mathies, R. A. Vibrational structure of the S2 (1Bu) excited state of diphenyloctatetraene observed by femtosecond stimulated Raman spectroscopy. Chem. Phys. Lett. 382, 81–86 (2003).

Shim, S., Stuart, C. M. & Mathies, R. A. Resonance Raman cross‐sections and vibronic analysis of rhodamine 6G from broadband stimulated Raman spectroscopy. ChemPhysChem 9, 697–699 (2008).

Abdolghader, P. et al. Unsupervised hyperspectral stimulated Raman microscopy image enhancement: denoising and segmentation via one-shot deep learning. Opt. Express 29, 34205 (2021).

Mandal, A., Erramilli, S. & Ziegler, L. D. Origin of dispersive line shapes in plasmonically enhanced femtosecond stimulated Raman spectra. J. Phys. Chem. C 120, 20998–21006 (2016).

Barak, A. et al. Solvent polarity governs ultrafast structural dynamics: a case study of 4-dimethylamino-4′-carbomethoxydiphenylacetylene. J. Phys. Chem. C 127, 5855–5865 (2023).

Tanaka, S. & Mukamel, S. Coherent X-ray Raman spectroscopy: a nonlinear local probe for electronic excitations. Phys. Rev. Lett. 89, 043001 (2002).

Liu, W. et al. Tracking ultrafast vibrational cooling during excited-state proton transfer reaction with anti-Stokes and Stokes femtosecond stimulated Raman spectroscopy. J. Phys. Chem. Lett. 8, 997–1003 (2017).

Bera, K., Kwang, S. Y., Cassabaum, A. A., Rich, C. C. & Frontiera, R. R. Facile background discrimination in femtosecond stimulated Raman spectroscopy using a dual-frequency Raman pump technique. J. Phys. Chem. A 123, 7932–7939 (2019).

Femtosecond spectroscopypdf

Polli, D., Kumar, V., Valensise, C. M., Marangoni, M. & Cerullo, G. Broadband coherent Raman scattering microscopy. Laser Photon Rev. 12, 1800020 (2018).

A nonlinear optical effect that occurs when the refractive index of a material changes, typically in a quadratic manner, in response to an applied electric field. Such a modification can affect the propagation of pulses and their spectral profiles.

Molesky, B. P., Guo, Z., Cheshire, T. P. & Moran, A. M. Perspective: two-dimensional resonance Raman spectroscopy. J. Chem. Phys. 145, 180901 (2016).

Fumero, G., Batignani, G., Dorfman, K. E., Mukamel, S. & Scopigno, T. On the resolution limit of femtosecond stimulated Raman spectroscopy: modelling fifth-order signals with overlapping pulses. ChemPhysChem 16, 3438–3443 (2015).

Femtosecond spectroscopywikipedia

Batignani, G. et al. Probing ultrafast photo-induced dynamics of the exchange energy in a Heisenberg antiferromagnet. Nat. Photon. 9, 506–510 (2015). This article presents the measurement of sub-100-fs dynamics in a solid-state sample with high-resolution FSRS.

Oscar, B. G., Chen, C., Liu, W., Zhu, L. & Fang, C. Dynamic Raman line shapes on an evolving excited-state landscape: insights from tunable femtosecond stimulated Raman spectroscopy. J. Phys. Chem. A 121, 5428–5441 (2017).

Nakamura, R., Hamada, N., Abe, K. & Yoshizawa, M. Ultrafast hydrogen-bonding dynamics in the electronic excited state of photoactive yellow protein revealed by femtosecond stimulated Raman spectroscopy. J. Phys. Chem. B 116, 14768–14775 (2012).

Provencher, F. et al. Direct observation of ultrafast long-range charge separation at polymer–fullerene heterojunctions. Nat. Commun. 5, 4288 (2014).

Rohringer, N. X-ray Raman scattering: a building block for nonlinear spectroscopy. Phil. Trans. R. Soc. 377, 20170471 (2019).

Batignani, G., Fumero, G., Mai, E., Martinati, M. & Scopigno, T. Stimulated Raman lineshapes in the large light–matter interaction limit. Opt. Mater. X 13, 100134 (2022).

Batignani, G., Fumero, G., Mukamel, S. & Scopigno, T. Energy flow between spectral components in 2D broadband stimulated Raman spectroscopy. Phys. Chem. Chem. Phys. 17, 10454–10461 (2015).

Kloz, M., van Grondelle, R. & Kennis, J. T. M. Wavelength-modulated femtosecond stimulated Raman spectroscopy — approach towards automatic data processing. Phys. Chem. Chem. Phys. 13, 18123 (2011).

Al Osipov, V., Asban, S. & Mukamel, S. Time and frequency resolved transient-absorption and stimulated-Raman signals of stochastic light. J. Chem. Phys. 151, 044113 (2019).

Kumar, P. et al. Excited-state proton transfer dynamics in LSSmOrange studied by time-resolved impulsive stimulated Raman spectroscopy. J. Phys. Chem. Lett. 12, 7466–7473 (2021).

Femtosecond spectroscopyprinciple

Fingerhut, B. P., Dorfman, K. E. & Mukamel, S. Probing the conical intersection dynamics of the RNA base uracil by UV-pump stimulated-Raman-probe signals; ab initio simulations. J. Chem. Theory Comput. 10, 1172–1188 (2014).

Frontiera, R. R., Henry, A.-I., Gruenke, N. L. & Van Duyne, R. P. Surface-enhanced femtosecond stimulated Raman spectroscopy. J. Phys. Chem. Lett. 2, 1199–1203 (2011). This article is an early demonstration of surface-enhanced FSRS.

Ultrafastspectroscopypdf

Wahab, M. F. & O’Haver, T. C. Wavelet transforms in separation science for denoising and peak overlap detection. J. Sep. Sci. 43, 1998–2010 (2020).

Silva, W. R., Keller, E. L. & Frontiera, R. R. Determination of resonance Raman cross-sections for use in biological SERS sensing with femtosecond stimulated Raman spectroscopy. Anal. Chem. 86, 7782–7787 (2014).

Kukura, P., McCamant, D. W. & Mathies, R. A. Femtosecond time-resolved stimulated Raman spectroscopy of the S2 (1Bu+) excited state of β-carotene. J. Phys. Chem. A 108, 5921–5925 (2004).

The profile of the pulse’s intensity as a function of time. It describes how the intensity of the pulse varies over time, characterizing the peak intensity, the duration and any modulations or variations in intensity within that duration.

Lockard, J. V., Butler Ricks, A., Co, D. T. & Wasielewski, M. R. Interrogating the intramolecular charge-transfer state of a julolidine−anthracene donor−acceptor molecule with femtosecond stimulated Raman spectroscopy. J. Phys. Chem. Lett. 1, 215–218 (2010).

First demonstrated in 1994, femtosecond stimulated Raman scattering (FSRS) has gained popularity since the early 2000s as an ultrafast pump–probe vibrational spectroscopy technique with the potential to circumvent the time and energy limitations imposed by the Heisenberg uncertainty principle. This Primer explores whether, why, when and how the temporal precision and frequency resolution of traditional time-resolved spontaneous Raman spectroscopy can be surpassed by its coherent counterpart (FSRS), while still adhering to the uncertainty principle. We delve into the fundamental concepts behind FSRS and its most common experimental implementations, focusing on instrumentation details, measurement techniques, data analysis and modelling. This includes discussions on synthesizing the Raman pump beam, artificial intelligence (AI)-assisted baseline removal methods and analytical expressions for reproducing experimental data and extracting key parameters such as relaxation times and out-of-equilibrium temperature profiles. Recent applications of FSRS from physics, chemistry and biology are showcased, demonstrating how this approach has facilitated cross-disciplinary studies. We also address the technical and conceptual limitations of FSRS to aid in designing optimal experiments based on specific goals. Finally, we explore future directions, including multidimensional extensions to address vibrational couplings and the use of quantum light to untangle temporal and spectral resolution.

Shenje, L., Qu, Y., Popik, V. & Ullrich, S. Femtosecond photodecarbonylation of photo-ODIBO studied by stimulated Raman spectroscopy and density functional theory. Phys. Chem. Chem. Phys. 23, 25637–25648 (2021).

Barclay, M. S., Caricato, M. & Elles, C. G. Femtosecond stimulated Raman scattering from triplet electronic states: experimental and theoretical study of resonance enhancements. J. Phys. Chem. A 123, 7720–7732 (2019).

Ploetz, E., Marx, B., Klein, T., Huber, R. & Gilch, P. A 75 MHz light source for femtosecond stimulated Raman microscopy. Opt. Express 17, 18612 (2009).

Fremout, W. & Saverwyns, S. Identification of synthetic organic pigments: the role of a comprehensive digital Raman spectral library. J. Raman Spectrosc. 43, 1536–1544 (2012).

Hall, C. R. et al. Ultrafast dynamics in light-driven molecular rotary motors probed by femtosecond stimulated Raman spectroscopy. J. Am. Chem. Soc. 139, 7408–7414 (2017).

Hontani, Y. et al. Spectroscopic and computational observation of glutamine tautomerization in the blue light sensing using flavin domain photoreaction. J. Am. Chem. Soc. 145, 1040–1052 (2023).

Wei, J. et al. Tracking ultrafast structural dynamics in a dual-emission anti-Kasha-active fluorophore using femtosecond stimulated Raman spectroscopy. J. Phys. Chem. Lett. 12, 4466–4473 (2021).

Chen, C. et al. Photoinduced proton transfer of GFP-inspired fluorescent superphotoacids: principles and design. J. Phys. Chem. B 123, 3804–3821 (2019).

Roy, P., Al-Kahtani, F., Cammidge, A. N. & Meech, S. R. Solvent tuning excited state structural dynamics in a novel bianthryl. J. Phys. Chem. Lett. 14, 253–259 (2023).

Dasgupta, J., Frontiera, R. R., Taylor, K. C., Lagarias, J. C. & Mathies, R. A. Ultrafast excited-state isomerization in phytochrome revealed by femtosecond stimulated Raman spectroscopy. Proc. Natl Acad. Sci. USA 106, 1784–1789 (2009).

Weigel, A. & Ernsting, N. P. Excited stilbene: intramolecular vibrational redistribution and solvation studied by femtosecond stimulated Raman spectroscopy. J. Phys. Chem. B 114, 7879–7893 (2010).

Roy, P. et al. Ultrafast bridge planarization in donor-π-acceptor copolymers drives intramolecular charge transfer. Nat. Commun. 8, 1716 (2017).

Mukamel, S. & Biggs, J. D. Communication: comment on the effective temporal and spectral resolution of impulsive stimulated Raman signals. J. Chem. Phys. 134, 161101 (2011). Key discussion of FSRS resolution and the Heisenberg principle.

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

The energy difference with respect to the laser energy expressed in wavenumbers, evaluated as \(\Delta \widetilde{{\rm{\nu }}}\) (in units of cm–1) = 107 × (\({\lambda }_{{\rm{L}}}^{-1}\) – λ−1) (where wavelength is in units of nm).

Wahl, J., Sjödahl, M. & Ramser, K. Single-step preprocessing of Raman spectra using convolutional neural networks. Appl. Spectrosc. 74, 427–438 (2020).

Lessing, H. E. & Von Jena, A. Separation of rotational diffusion and level kinetics in transient absorption spectroscopy. Chem. Phys. Lett. 42, 213–217 (1976).

Zhao, Z., Pu, R., Wang, Z., Jiang, J. & Liu, W. Identification of ultraviolet photoinduced presolvated electrons in water as the reducing agent in the photoreduction of graphene oxide. J. Phys. Chem. C 127, 3516–3522 (2022).

Karmakar, S. et al. Transient Raman snapshots of the twisted intramolecular charge transfer state in a stilbazolium dye. J. Phys. Chem. Lett. 11, 4842–4848 (2020).

Audier, X., Heuke, S., Volz, P., Rimke, I. & Rigneault, H. Noise in stimulated Raman scattering measurement: from basics to practice. APL Photon. 5, 011101 (2020).

Mukamel, S., Healion, D., Zhang, Y. & Biggs, J. D. Multidimensional attosecond resonant X-ray spectroscopy of molecules: lessons from the optical regime. Annu. Rev. Phys. Chem. 64, 101–127 (2013).

Femtosecond spectroscopyNobel Prize

The basic medium of fiber optics is a hair-thin fiber that is sometimes made of plastic but most often of glass. A typical glass optical fiber has a diameter of 125 micrometres (μm), or 0.125 mm (0.005 inch). This is actually the diameter of the cladding, or outer reflecting layer. The core, or inner transmitting cylinder, may have a diameter as small as 10 μm. Through a process known as total internal reflection, light rays beamed into the fiber can propagate within the core for great distances with remarkably little attenuation, or reduction in intensity. The degree of attenuation over distance varies according to the wavelength of the light and to the composition of the fiber.

Umapathy, S., Mallick, B. & Lakshmanna, A. Mode-dependent dispersion in Raman line shapes: observation and implications from ultrafast Raman loss spectroscopy. J. Chem. Phys. 133, 024505 (2010).

Fiber optics, also spelled fibre optics, is the science of transmitting data, voice, and images by the passage of light through thin, transparent fibers.

Jen, M., Lee, S., Jeon, K., Hussain, S. & Pang, Y. Ultrafast intramolecular proton transfer of alizarin investigated by femtosecond stimulated Raman spectroscopy. J. Phys. Chem. B 121, 4129–4136 (2017).

Frontiera, R. R., Dasgupta, J. & Mathies, R. A. Probing interfacial electron transfer in coumarin 343 sensitized TiO2 nanoparticles with femtosecond stimulated Raman. J. Am. Chem. Soc. 131, 15630–15632 (2009).

Batignani, G. et al. Modeling the ultrafast response of two-magnon Raman excitations in antiferromagnets on the femtosecond timescale. Ann. Phys. 531, 1900439 (2019).

Dorfman, K. E., Schlawin, F. & Mukamel, S. Stimulated Raman spectroscopy with entangled light: enhanced resolution and pathway selection. J. Phys. Chem. Lett. 5, 2843–2849 (2014).

Liu, W., Han, F., Smith, C. & Fang, C. Ultrafast conformational dynamics of pyranine during excited state proton transfer in aqueous solution revealed by femtosecond stimulated Raman spectroscopy. J. Phys. Chem. B 116, 10535–10550 (2012).

Marx, C. A., Harbola, U. & Mukamel, S. Nonlinear optical spectroscopy of single, few, and many molecules: nonequilibrium Green’s function QED approach. Phys. Rev. A 77, 022110 (2008).

Lee, J., Challa, J. R. & McCamant, D. W. Ultraviolet light makes dGMP floppy: femtosecond stimulated Raman spectroscopy of 2′-deoxyguanosine 5′-monophosphate. J. Phys. Chem. B 121, 4722–4732 (2017).

Ashner, M. N. & Tisdale, W. A. High repetition-rate femtosecond stimulated Raman spectroscopy with fast acquisition. Opt. Express 26, 18331 (2018).

Ferrante, C., Pontecorvo, E., Cerullo, G., Vos, M. H. & Scopigno, T. Direct observation of subpicosecond vibrational dynamics in photoexcited myoglobin. Nat. Chem. 8, 1137–1143 (2016).

Takaya, T. & Iwata, K. Relaxation mechanism of β-carotene from S2 (1Bu+) state to S1 (2Ag–) state: femtosecond time-resolved near-IR absorption and stimulated resonance Raman studies in 900–1550 nm region. J. Phys. Chem. A 118, 4071–4078 (2014).

Liebel, M., Schnedermann, C., Wende, T. & Kukura, P. Principles and applications of broadband impulsive vibrational spectroscopy. J. Phys. Chem. A 119, 9506–9517 (2015).

Yoon, S. et al. Dependence of line shapes in femtosecond broadband stimulated Raman spectroscopy on pump–probe time delay. J. Chem. Phys. 122, 024505 (2005).

Stamm, J. A. & Dantus, M. A comparison of strategies for state‐selective coherent Raman excitation. J. Raman Spectrosc. 52, 2029–2037 (2021).

Batignani, G., Ferrante, C., Fumero, G. et al. Femtosecond stimulated Raman spectroscopy. Nat Rev Methods Primers 4, 34 (2024). https://doi.org/10.1038/s43586-024-00314-6

Sun, Z., Lu, J., Zhang, D. H. & Lee, S.-Y. Quantum theory of (femtosecond) time-resolved stimulated Raman scattering. J. Chem. Phys. 128, 144114 (2008).

Optical telecommunication is usually conducted with infrared light in the wavelength ranges of 0.8–0.9 μm or 1.3–1.6 μm—wavelengths that are efficiently generated by light-emitting diodes or semiconductor lasers and that suffer least attenuation in glass fibers. Fiberscope inspection in endoscopy or industry is conducted in the visible wavelengths, one bundle of fibers being used to illuminate the examined area with light and another bundle serving as an elongated lens for transmitting the image to the human eye or a video camera.

McCamant, D. W. Re-evaluation of rhodopsin’s relaxation kinetics determined from femtosecond stimulated Raman lineshapes. J. Phys. Chem. B 115, 9299–9305 (2011).

Kuramochi, H., Takeuchi, S. & Tahara, T. Ultrafast structural evolution of photoactive yellow protein chromophore revealed by ultraviolet resonance femtosecond stimulated Raman spectroscopy. J. Phys. Chem. Lett. 3, 2025–2029 (2012).

Sinjab, F., Liao, Z. & Notingher, I. Applications of spatial light modulators in Raman spectroscopy. Appl. Spectrosc. 73, 727–746 (2019).

Barclay, M. S., Quincy, T. J., Williams-Young, D. B., Caricato, M. & Elles, C. G. Accurate assignments of excited-state resonance Raman spectra: a benchmark study combining experiment and theory. J. Phys. Chem. A 121, 7937–7946 (2017).

Fumero, G. et al. Retrieving genuine nonlinear Raman responses in ultrafast spectroscopy via deep learning. Preprint at https://arxiv.org/abs/2309.16933 (2023).

Dorfman, K. E., Fingerhut, B. P. & Mukamel, S. Time-resolved broadband Raman spectroscopies: a unified six-wave-mixing representation. J. Chem. Phys. 139, 124113 (2013).

Kuramochi, H., Takeuchi, S., Kamikubo, H., Kataoka, M. & Tahara, T. Fifth-order time-domain Raman spectroscopy of photoactive yellow protein for visualizing vibrational coupling in its excited state. Sci. Adv. 5, eaau4490 (2023).

Marx, B., Czerwinski, L., Light, R., Somekh, M. & Gilch, P. Multichannel detectors for femtosecond stimulated Raman microscopy — ideal and real ones. J. Raman Spectrosc. 45, 521–527 (2014).

Laimgruber, S., Schachenmayr, H., Schmidt, B., Zinth, W. & Gilch, P. A femtosecond stimulated Raman spectrograph for the near ultraviolet. Appl. Phys. B 85, 557–564 (2006). To our knowledge, this article is the first demonstration of FSRS with a fixed-wavelength ultraviolet Raman pump.

Present address: Physical Measurement Laboratory, National Institutes of Standards and Technology, Gaithersburg, MD, USA

Batignani, G. et al. Excited-state energy surfaces in molecules revealed by impulsive stimulated Raman excitation profiles. J. Phys. Chem. Lett. 12, 9239–9247 (2021).

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Lee, S., Jen, M., Jang, T., Lee, G. & Pang, Y. Twisted intramolecular charge transfer of nitroaromatic push–pull chromophores. Sci. Rep. 12, 6557 (2022).

Hu, S., Morris, I. K., Singh, J. P., Smith, K. M. & Spiro, T. G. Complete assignment of cytochrome c resonance Raman spectra via enzymic reconstitution with isotopically labeled hemes. J. Am. Chem. Soc. 115, 12446–12458 (1993).

Tahara, S., Kuramochi, H., Takeuchi, S. & Tahara, T. Protein dynamics preceding photoisomerization of the retinal chromophore in bacteriorhodopsin revealed by deep-UV femtosecond stimulated Raman spectroscopy. J. Phys. Chem. Lett. 10, 5422–5427 (2019).

Glenn, R. & Dantus, M. Single broadband phase-shaped pulse stimulated Raman spectroscopy for standoff trace explosive detection. J. Phys. Chem. Lett. 7, 117–125 (2016).

Batignani, G., Ferrante, C. & Scopigno, T. Accessing excited state molecular vibrations by femtosecond stimulated Raman spectroscopy. J. Phys. Chem. Lett. 11, 7805–7813 (2020).

Molesky, B. P., Guo, Z. & Moran, A. M. Femtosecond stimulated Raman spectroscopy by six-wave mixing. J. Chem. Phys. 142, 212405 (2015).

Polli, D., Brida, D., Mukamel, S., Lanzani, G. & Cerullo, G. Effective temporal resolution in pump-probe spectroscopy with strongly chirped pulses. Phys. Rev. A 82, 053809 (2010).

Stiles, P. L., Dieringer, J. A., Shah, N. C. & Van Duyne, R. P. Surface-enhanced Raman spectroscopy. Annu. Rev. Anal. Chem. 1, 601–626 (2008).

Burns, K. H., Quincy, T. J. & Elles, C. G. Excited-state resonance Raman spectroscopy probes the sequential two-photon excitation mechanism of a photochromic molecular switch. J. Chem. Phys. 157, 234302 (2022).

Prince, R. C., Frontiera, R. R. & Potma, E. O. Stimulated Raman scattering: from bulk to nano. Chem. Rev. 117, 5070–5094 (2017).

Tang, L. et al. Unraveling ultrafast photoinduced proton transfer dynamics in a fluorescent protein biosensor for Ca2+ imaging. Chem. A Eur. J. 21, 6481–6490 (2015).

Pontecorvo, E., Ferrante, C., Elles, C. G. & Scopigno, T. Spectrally tailored narrowband pulses for femtosecond stimulated Raman spectroscopy in the range 330–750 nm. Opt. Express 21, 6866–6872 (2013).

Femtosecond spectroscopyapplications

Buchanan, L. E. et al. Surface-enhanced femtosecond stimulated Raman spectroscopy at 1 MHz repetition rates. J. Phys. Chem. Lett. 7, 4629–4634 (2016).

Grumstrup, E. M. et al. Frequency modulated femtosecond stimulated Raman spectroscopy of ultrafast energy transfer in a donor–acceptor copolymer. J. Phys. Chem. B 117, 8245–8255 (2013).

Henstridge, M., Först, M., Rowe, E., Fechner, M. & Cavalleri, A. Nonlocal nonlinear phononics. Nat. Phys. 18, 457–461 (2022). This article describes the probing phonon polariton via FSRS upon terahertz actinic pump excitation.

Valensise, C. M. et al. Removing non-resonant background from CARS spectra via deep learning. APL Photon. 5, 061305 (2020).

Krueger, T. D., Tang, L. & Fang, C. Delineating ultrafast structural dynamics of a green-red fluorescent protein for calcium sensing. Biosensors 13, 218 (2023).

Quincy, T. J., Barclay, M. S., Caricato, M. & Elles, C. G. Probing dynamics in higher-lying electronic states with resonance-enhanced femtosecond stimulated Raman spectroscopy. J. Phys. Chem. A 122, 8308–8319 (2018).

Solaris, J., Krueger, T. D., Chen, C. & Fang, C. Photogrammetry of ultrafast excited-state intramolecular proton transfer pathways in the fungal pigment draconin red. Molecules 28, 3506 (2023).

Kayal, S., Roy, K. & Umapathy, S. Femtosecond coherent nuclear dynamics of excited tetraphenylethylene: ultrafast transient absorption and ultrafast Raman loss spectroscopic studies. J. Chem. Phys. 148, 024301 (2018).

Shim, S., Dasgupta, J. & Mathies, R. A. Femtosecond time-resolved stimulated Raman reveals the birth of bacteriorhodopsin’s J and K intermediates. J. Am. Chem. Soc. 131, 7592–7597 (2009).

Diaz, S. A. & McCamant, D. W. Diffuse reflectance-based femtosecond stimulated Raman spectroscopy of opaque suspensions. Anal. Chem. 95, 15856–15860 (2023).

Krueger, T. D. et al. Ultrafast triplet state formation in a methylated fungi-derived pigment: toward rational molecular design for sustainable optoelectronics. J. Phys. Chem. C 125, 17565–17572 (2021).

Batignani, G. et al. Genuine dynamics vs cross phase modulation artifacts in femtosecond stimulated Raman spectroscopy. ACS Photon. 6, 492–500 (2019).

Han, F., Liu, W. & Fang, C. Excited-state proton transfer of photoexcited pyranine in water observed by femtosecond stimulated Raman spectroscopy. Chem. Phys. 422, 204–219 (2013).

Potma, E. O. & Mukamel, S. Theory of coherent Raman scattering. In Coherent Raman Scattering Microscopy (eds Cheng, J.-X. & Xie, X. S.) (CRC Press, 2012).

fiber optics, the science of transmitting data, voice, and images by the passage of light through thin, transparent fibers. In telecommunications, fiber optic technology has virtually replaced copper wire in long-distance telephone lines, and it is used to link computers within local area networks. Fiber optics is also the basis of the fiberscopes used in examining internal parts of the body (endoscopy) or inspecting the interiors of manufactured structural products.

Barton, S., Alakkari, S., O’Dwyer, K., Ward, T. & Hennelly, B. Convolution network with custom loss function for the denoising of low SNR Raman spectra. Sensors 21, 4623 (2021).

Silberberg, Y. Quantum coherent control for nonlinear spectroscopy and microscopy. Annu. Rev. Phys. Chem. 60, 277–292 (2009).

Robben, K. C. & Cheatum, C. M. Edge-pixel referencing suppresses correlated baseline noise in heterodyned spectroscopies. J. Chem. Phys. 152, 094201 (2020).

Lim, S., Chon, B., Rhee, H. & Cho, M. Spectral modulation of stimulated Raman scattering signal: beyond weak Raman pump limit. J. Raman Spectrosc. 49, 607–620 (2018).

Takaya, T. & Iwata, K. Development of a femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer in resonance with transitions in the 900–1550 nm region. Analyst 141, 4283–4292 (2016).

The authors are grateful to G. Cerullo, P. Kukura, S. Mukamel and M. H. Vos for several inspiring discussions. They acknowledge early contributions by E. Pontecorvo to the planning and development of their first FSRS prototype. G.B. acknowledges funding from the PRIN 2022 Project (Dynamat) (grant number 2022PR7CCY).

Verma, P. et al. Excited-state symmetry breaking in quadrupolar pull–push–pull molecules: dicyanovinyl vs. cyanophenyl acceptors. Phys. Chem. Chem. Phys. 25, 22689–22699 (2023).

Young, R. M. et al. Ultrafast conformational dynamics of electron transfer in ExBox4+⊂perylene. J. Phys. Chem. A 117, 12438–12448 (2013).

Kloz, M., Weißenborn, J., Polívka, T., Frank, H. A. & Kennis, J. T. M. Spectral watermarking in femtosecond stimulated Raman spectroscopy: resolving the nature of the carotenoid S* state. Phys. Chem. Chem. Phys. 18, 14619–14628 (2016).

UltrafastSpectroscopyapplication

Hall, C. R. et al. Femtosecond stimulated Raman study of the photoactive flavoprotein AppABLUF. Chem. Phys. Lett. 683, 365–369 (2017).

Fang, C. & Tang, L. Mapping structural dynamics of proteins with femtosecond stimulated Raman spectroscopy. Annu. Rev. Phys. Chem. 71, 239–265 (2020).

Bera, K., Douglas, C. J. & Frontiera, R. R. Femtosecond stimulated Raman spectroscopy-guided library mining leads to efficient singlet fission in rubrene derivatives. Chem. Sci. 12, 13825–13835 (2021).

Mukamel, S. Multidimensional femtosecond correlation spectroscopies of electronic and vibrational excitations. Annu. Rev. Phys. Chem. 51, 691–729 (2000).

Creelman, M., Kumauchi, M., Hoff, W. D. & Mathies, R. A. Chromophore dynamics in the PYP photocycle from femtosecond stimulated Raman spectroscopy. J. Phys. Chem. B 118, 659–667 (2014).

Hoffman, D. P., Valley, D., Ellis, S. R., Creelman, M. & Mathies, R. A. Optimally shaped narrowband picosecond pulses for femtosecond stimulated Raman spectroscopy. Opt. Express 21, 21685 (2013).

Yoshizawa, M., Hattori, Y. & Kobayashi, T. Femtosecond time-resolved resonance Raman gain spectroscopy in polydiacetylene. Phys. Rev. B 49, 13259–13262 (1994). To our knowledge, the first demonstration of femtosecond stimulated Raman scattering (FSRS) with 300-fs temporal precision.

Farrow, G. A. et al. On the intersystem crossing rate in a platinum(ii) donor–bridge–acceptor triad. Phys. Chem. Chem. Phys. 23, 21652–21663 (2021).

Gautam, R., Vanga, S., Ariese, F. & Umapathy, S. Review of multidimensional data processing approaches for Raman and infrared spectroscopy. EPJ Tech. Instrum. 2, 8 (2015).

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Raman transitions occurring from vibrationally excited levels (n > 0) to the subsequent higher state (n + 1), typically resulting in a red-shifted line with respect to the fundamental transition (from n = 0 to n = 1).

Roy, P., Browne, W. R., Feringa, B. L. & Meech, S. R. Ultrafast motion in a third generation photomolecular motor. Nat. Commun. 14, 1253 (2023).

Monacelli, L. et al. Manipulating impulsive stimulated Raman spectroscopy with a chirped probe pulse. J. Phys. Chem. Lett. 8, 966–974 (2017).

Zhao, J., Lui, H., McLean, D. I. & Zeng, H. Automated autofluorescence background subtraction algorithm for biomedical Raman spectroscopy. Appl. Spectrosc. 61, 1225–1232 (2007).