Stimulated Raman Scattering Microscopy with an All-Optical Modulator

Abstract

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 fiberfeedback 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 highspeed, 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.

Multi-color stimulated Raman scattering with a frame-to-frame wavelength-tunable fiber-based light source

“…For the later SRS measurements an fiber-integrated electro-optic modulator (EOM) in combination with a polarizing beam splitter (PBS) in the FOPO was used to modulate the amplitude of the circulating signal pulses at the half of the repetition rate, by sending every second pulse of the FOPO into the beam dump (BD) of the SRS module. The threshold behaviour of the FOPO was then exploited to achieve a 100 % modulation depth, which is typically not possible with external modulators [29][30][31], but beneficial for SRS imaging, as the amount of the SRS signal scales linearly with the modulation depth [12]. 1.…”