Stimulated Raman scattering (SRS) has attracted increasing attention in bio-imaging because of the ability toward background-free molecular-specific acquisitions without fluorescence labeling. Nevertheless, the corresponding sensitivity and specificity remain far behind those of fluorescence techniques. Here, we demonstrate SRS spectro-microscopy driven by a multiple-plate continuum (MPC), whose octave-spanning bandwidth (600-1300 nm) and high spectral energy density (∼1 nJ/cm-1) enable spectroscopic interrogation across the entire Raman active region (0-4000 cm-1), SRS imaging of a Drosophila brain, and electronic pre-resonance (EPR) detection of a fluorescent dye. We envision that utilizing MPC light source will substantially enhance the sensitivity and specificity of SRS by implementing EPR mode and spectral multiplexing via accessing three or more coherent wavelengths.
We propose a new architecture, double-pass multiple-plate continuum (DPMPC), for nonlinear pulse compression. In addition to having a smaller footprint, a double-pass configuration is designed to achieve substantial bandwidth broadening without incurring noticeable higher-order dispersion, thus improving the temporal contrast over those of the traditional single-pass geometry when only the quadratic spectral phase can be compensated. In our proof-of-concept experiment, 187 μJ, 190-fs Yb-based laser pulse is compressed to 20 fs with high throughput (75%), high Strehl ratio (0.76), and excellent beam homogeneity by using DPMPC. The subsequently generated octave-spanning spectrum exhibits a significantly raised blue tail compared with that driven by pulses from a single-pass counterpart.
Stimulated Raman scattering (SRS) spectromicroscopy is
a powerful
technique that enables label-free detection of chemical bonds with
high specificity. However, the low Raman cross section due to typical
far-electronic resonance excitation seriously restricts the sensitivity
and undermines its application to bio-imaging. To address this bottleneck,
the electronic preresonance (EPR) SRS technique has been developed
to enhance the Raman signals by shifting the excitation frequency
toward the molecular absorption. A fundamental weakness of the previous
demonstration is the lack of dual-wavelength tunability, making EPR-SRS
only applicable to a limited number of species in the proof-of-concept
experiment. Here, we demonstrate the EPR-SRS spectromicroscopy using
a multiple-plate continuum (MPC) light source able to examine a single
vibration mode with independently adjustable pump and Stokes wavelengths.
In our experiments, the CC vibration mode of Alexa 635 is
interrogated by continuously scanning the pump-to-absorption frequency
detuning throughout the entire EPR region enabled by MPC. The results
exhibit 150-fold SRS signal enhancement and good agreement with the
Albrecht A-term preresonance model. Signal enhancement is also observed
in EPR-SRS images of the whole Drosophila brain stained
with Alexa 635. With the improved sensitivity and potential to implement
hyperspectral measurement, we envision that MPC-EPR-SRS spectromicroscopy
can bring the Raman techniques closer to a routine in bio-imaging.
The exploration of deactivation mechanisms for near-infrared(NIR)-emissive organic molecules has been a key issue in chemistry, materials science and molecular biology. In this study, based on transient absorption spectroscopy and transient grating photoluminescence spectroscopy, we demonstrate that the aggregated Pt II complex 4H (efficient NIR emitter) exhibits collective out-of-plane motions with a frequency of 32 cm À 1 (0.96 THz) in the excited states. Importantly, similar THz characteristics were also observed in analogous Pt II complexes with prominent NIR emission efficiency. The conservation of THz motions enables excited-state deactivation to proceed along low-frequency vibrational coordinates, contributing to the suppression of nonradiative decay and remarkable NIR emission. These novel results highlight the significance of excited-state vibrations in nonradiative processes, which serve as a benchmark for improving device performance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.