Photothermal Microscopy and
Spectroscopy Webinar

Stimulated Raman scattering (SRS) microscopy has shown enormous potential in revealing molecular structures, dynamics and couplings in complex systems. Yet, the sensitivity of SRS is fundamentally limited to milli-molar level due to the shot noise and the small modulation depth. Additionally the operation of SRS imaging is complicated by cross phase modulation. To overcome these challenges, we recently revisited SRS from the perspective of energy deposition. The SRS process pumps molecules to their vibrationally excited states. The thereafter relaxation heats up the surrounding and induces refractive index changes. By probing the refractive index changes with a laser beam, we have developed stimulated Raman photothermal (SRP) microscopy, where a > 500-fold boost of modulation depth is achieved. Moreover, SRP imaging can be operated with a noisy fiber laser for excitation and a long working distance air condenser for signal collection. Versatile applications of SRP microscopy on viral particles, cells, and tissues are demonstrated. SRP microscopy opens a way to perform vibrational spectroscopic imaging with ultrahigh sensitivity and speed.