Mapping impurity of single-walled carbon nanotubes in bulk samples with multiplex coherent anti-stokes Raman microscopy

Enhanced double resonance Raman scattering in multilayer graphene with broadband coherent anti-Stokes Raman spectroscopy

Graphene's unique gapless band structure and remarkably large third-order optical susceptibility have drawn significant attention to its nonlinear optical response, particularly in the context of coherent anti-Stokes Raman scattering (CARS). Under the combined influence of phononic and electronic resonances, the CARS response of graphene has been observed to exhibit a distinctive feature of time-resolved dip-to-peak evolution. Here, we report a greatly enhanced double resonance Raman mode beyond the G mode of multi-layer graphene with broadband CARS measurements. The significant difference in the intensity ratio between CARS and SR for this mode may be attributed to the preferential activation of low-frequency phonons in the impulsive stimulated Raman scattering process (ISRS) and a lower dephasing rate. Our results build on a foundation towards a deeper exploration of the coherent Raman response of two-dimensional materials.

Enhancement of coherent anti-Stokes Raman signal via tailored probing in spectral focusing

A novel approach for spectral focusing using a single-beam coherent anti-Stokes Raman scattering setup with a pulse shaper controlling the phase and amplitude is presented. By identifying the frequencies acting as the pump, Stokes, and probe, the high degree of control can be exploited in order to specifically and independently tailor the spectral region to act only as probe to achieve the highest signal intensity. While maintaining the optimal excitation of the vibrational coherence, a signal increase by a factor of six in comparison with usual spectral focusing schemes is readily obtained. The signal improvement and contrast is demonstrated on human skin tissue.

Compact, low-noise, all-solid-state laser system for stimulated Raman scattering microscopy

We present a highly stable and compact laser source for stimulated Raman scattering (SRS) microscopy. cw-seeding of an optical parametric amplifier pumped by a bulk femtosecond Yb-oscillator and self-phase modulation in a tapered fiber allow for broad tunability without any optical or electronic synchronization. The source features noise levels of the Stokes beam close to the shot-noise limit at MHz modulation frequencies. We demonstrate the superior performance of our system by SRS imaging of micrometer-sized polymer beads.