Fig. 1: Independently tunable ER-SRS microscope and its application to Rho800 fluorophore.
From: Fluorescence-free single-molecule microscopy via electronic resonance stimulated Raman scattering
A Energy diagram of two-beam EPR-SRS (left) and ER-SRS (right) processes, where the frequency difference between the pump and Stokes beams is resonant to the vibrational transition. In ER-SRS (right), the pump beam is rigorously resonant to the electronic transition while in EPR-SRS (left), the pump beam is slightly off-resonant but still close to the electronic transition. B Two-beam ER-SRS instrument with synchronously pumped double OPO system with two independently tunable OPOs whose signal beams are each used as the pump and Stokes beams. C Absorption and emission spectra of Rho800 and the wavelength combinations of pump and Stokes used for collecting ER-SRS spectra. D ER-SRS spectra with various combinations of the pump and Stokes wavelengths indicated in (C). SR gain signal is plotted against the frequency differences between the pump and Stokes beams. Powers are set as 5 mW for pump and 5 mW for Stokes. Lines indicate spline interpolation. Error bars represent the mean ± standard deviation (n = 5). E Signal and background intensities in the ER-SRS spectra in (D) plotted against the pump wavelengths. Intensities are reported in arbitrary units (a.u.).
