(Color online) Schematic optical layout, as described in text. BBO: Nonlinear optic (-BBO, for sum-frequency generation); BS: Beam splitter; CL: Cylindrical lens; DBS: Dichroic beam splitter; G: Grating; OPA: Optical parametric amplifier; TS: Translation stage.
(Color) (a) Spectrally integrated time-resolved signal from neat toluene as function of probe delay, , with Fourier transform (FT, inset). Dashed line in FT denotes beat frequency that is poorly resolved in integrated signal FT. (b) Spectrally dispersed time-resolved signal from neat toluene (contour plot of spectral intensity, normalized to peak near ); anti-Stokes energies measured relative to centered at . FTs of frequency slices denoted by are shown in Figs. 3(a)–3(c), respectively, following removal of exponentially decaying baseline.
Fourier transforms (FTs) of frequency slices shown in Fig. 2(b). Dashed line represents beat frequency poorly resolved in Fig. 2(a), demonstrating a benefit of spectral resolution of tr-CARS signal.
(Color) Numerical simulation of spectrally resolved tr-CARS data from toluene, shown as contour plot of spectral intensity, normalized to peak near .
Experimental integrated signal (solid curve) in fs/ps CARS studies of neat toluene, shown as a function of probe delay, (bottom axis). Arrow denotes optimal timing for spectrally resolved fs/ps CARS data shown in Fig. 6. Pulse duration and profile compare well with numerical simulation (dashed curve) of optimal pulse temporal profile, assuming a square wave slit, plotted at its optimal delay relative to and pulses (top axis).
(a) Experimental fs/ps CARS signal from neat toluene, normalized to the peak intensity (details in text); (b) Simulation of toluene CARS signal using narrowband pulse for . Dashed curve represents simulated spectrum independent of instrument response; solid curve includes convolution with (FWHM) Gaussian spectrometer response.
(Color) (a) Spectrally dispersed time-resolved CARS signal from R6G in methanol, shown as contour plot of spectral intensity (contour color scheme analogous to that of Fig. 4); frequencies measured relative to centered at ; (b) FT of this spectrally dispersed CARS signal, shown as contour plot; (c) Spectrum of R6G in methanol obtained using fs/ps CARS method.
fs/ps CARS signal from neat chloroform, normalized to the peak intensity.
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