Coherent Nonlinear Raman Microscopies promise label-free, chemical-specific imaging at sensitivities orders of magnitude greater than conventional Spontaneous Raman Scattering Microscopy. We review the basic concepts and techniques and discuss the important competing background processes (cross-phase modulation, two-photon absorption, thermal lensing etc.) which significantly reduce both contrast and sensitivity in Coherent Raman Microscopy. We present and demonstrate a novel modulation scheme, Chirp Modulation, which removes all background signals in Stimulated Raman Scattering.
Reference: Optics Express 32, 31297-31310 (2024)