Double modulation SRS and SREF microscopy: signal contributions under pre-resonance conditions.

Area of Science:

• Spectroscopy
• Microscopy
• Chemical Physics

Background:

• Pre-electronic resonance enhancement boosts non-linear Raman microscopy sensitivity.
• Background signal generation from photophysical processes hinders sensitivity.

Purpose of the Study:

• To develop a novel detection scheme for stimulated Raman scattering (SRS) microspectroscopy.
• To enable parallel detection of stimulated Raman loss (SRL) and gain (SRG).
• To quantitatively analyze background signal sources in SRS.

Main Methods:

• Simultaneous modulation of pump and Stokes beams in SRS setup.
• Spectrally and temporally resolved measurements.
• Analysis of rhodamine dye signals.

Main Results:

• The novel scheme allows parallel SRL and SRG detection.
• Quantitative analysis of background signal contributions (two-photon absorption, stimulated emission).
• Identified contributions to SRL, SRG, and stimulated Raman excited fluorescence signals.

Conclusions:

• The developed detection scheme provides insights into background signal origins.
• Results offer guidelines for enhancing non-linear Raman microspectroscopy sensitivity.
• Enables improved single-molecule detection in pre-resonance conditions.