We demonstrate a compact laser platform that integrates stimulated and coherent Raman microscopy with high-resolution nonlinear Raman spectroscopy. Ultrashort laser pulses with a carefully managed, broadly tunable chirp are shown to enable a comfortable switching between the high-contrast microscopy and high-resolution spectroscopy modalities in both stimulated and coherent versions of nonlinear Raman scattering. Sub-10-cm À1 spectral resolution in stimulated Raman spectroscopy is demonstrated through a careful compensation of nonlinear phase distortions of ultrashort laser pulses. This offers a powerful tool for a reliable identification of molecular vibrations with close frequencies, enhancing the chemical selectivity of spectroscopic analysis of complex multicomponent systems. Introduction and Wolfgang Kiefer's legacyHigh-resolution spectroscopic analysis and ultrafast, short-pulse interrogation are the two main modalities of optical technologies based on nonlinear Raman scattering. [1,2] While high-resolution Raman spectroscopy [3,4] requires narrowband probes, capable of resolving individual molecular or atomic features in often crowded Raman spectra of complex chemical systems, broadband, shortpulse drivers offer a vast arsenal of tools [5,6] for time-resolved studies of ultrafast dynamics in physical, chemical, and biological systems [1,2,7] and open a whole new world of chemically specific, high-speed nonlinear microscopy. [8][9][10] The requirements on laser fields needed to implement these modalities are seemingly incompatible.Wolfgang Kiefer, one of the pioneers of the field of Raman spectroscopy, whose work had a profound impact on the field and who prominently contributed to the development of high-spectralresolution Raman methods, [11,12] was also among the first visionary scientists who recognized the tremendous potential of emerging short-pulse laser sources for Raman technologies. [13][14][15] This vision has in many ways shaped the future of the field. Within the past two decades, nonlinear Raman processes driven by ultrashort pulses have played a central role in ultrafast science, providing methods that help to probe [16,17] and control [18][19][20][21] ultrafast processes on the picosecond, femtosecond, and attosecond time scale, [22] as well as open new horizons in standoff detection [23,24] and ultrashort waveform synthesis. [25,26] With a powerful impetus gained from the invention of nonlinear Raman microscopy, [8,27] short-pulse Raman techniques find growing applications in bioimaging, enabling a chemically selective, high-frame-rate detection of intracellular dynamics, [28] diagnostics of lipid membranes, [29] and neurophysiological studies. [30][31][32][33][34] Ultrashort laser pulses inevitably impose limitations on the spectral resolution in nonlinear-optical microspectroscopy, making it difficult to resolve closely lying and overlapping lines in Raman spectra and to extract the informative signal in the microscopy of multicomponent biological systems. However, the coherence of laser p...

We propose simple, yet efficient strategies of pulse-width optimization applicable for nonlinear Raman brain imaging. With the spectral bandwidth of laser pulses accurately matched against the bandwidth of molecular vibrations, the coherent Raman signal is shown to be radically enhanced, enabling higher sensitivities and higher frame rates in nonlinear Raman brain imaging. As a specific example, we show that subpicosecond pulses offer a powerful tool for the detection of brain tumors using stimulated Raman microscopy, as they provide a strong signal without compromising the molecular specificity.

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