Stimulated Raman Scattering Microscopy with an All-Optical Modulator

Nonlinear phenomena are a frequent occurrence in nature and inherent to many optical systems. Nevertheless, nonlinearities are often avoided or suppressed in optical resonators. Here we demonstrate the application of nonlinear phenomena to pump-probe spectroscopy by using period doubling in a fiber-feedback optical parametric oscillator. On the basis of an analysis of the optical single-pulse spectra and successive second-harmonic spectra, we introduce a method to enhance the pulse-energy modulation depth to the level of conventional high-frequency modulators. We find that the modulator is suitable for high-speed, low-noise stimulated Raman scattering imaging with performance equal to that of acousto-optic modulation. The concept removes the need for electronic synchronization, reduces the detection effort and artifacts, and has great potential in terms of scalability of the modulation frequency.