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. Author manuscript; available in PMC: 2019 Jun 1.
Published in final edited form as: Top Catal. 2018 Apr 17;61(9-11):1101–1124. doi: 10.1007/s11244-018-0924-3

Figure 4.

Figure 4

a) Short-pulsed excitation pump and Stokes lasers may produce SRS and CARS signals, which can be detected in nonlinear microscopes. By fast modulation of either the pump or the Stokes beam, coupled with a lock-in-amplifier, signals can be detected with low noise levels. b) Left: While interference with a nonresonant (dotted) background can shift the maximum signal from the vibrational peak in CARS (blue squares), the SRS signal (red circles) remains similar to the corresponding spontaneous Raman signal (solid line) from retinol. Right: The SRS signal intensity has a simple linear intensity dependence on the analyte concentration. Figure 4b is reprinted with permission from ref. [8], copyright 2008 American Association for the Advancement of Science.