Track papers across labs, topics, and trends.
Search papers, labs, and topics across Lattice.
This paper uses FDTD simulations to study the impact of metal nanostructures (mirrors and cavities) on Raman scattering signals, focusing on the strong-coupling regime. They identify three key effects: enhanced local fields leading to increased excited state population, metal-induced relaxation and broadening of spectral lines (inherited by cavity polaritons), and interference effects between incident and reflected light that can modulate the Raman spectrum. The simulations reveal complex interactions between photonic materials and optical signals, including interference between Rabi contraction and Raman signals.
Metal nanostructures near molecules don't just enhance Raman signals; they fundamentally reshape them via cavity-induced relaxation, broadening, and interference effects.
We investigate how proximity to a metal nanostructure, particularly to a flat mirror or a cavity confined between two mirrors, affects the vibronic structure of Raman scattering signals. We find that such proximity, particularly for the strong-coupling situation encountered in cavity environments, plays multiple roles in shaping Raman signals beyond the now-familiar signal enhancement known as surface-enhanced Raman scattering (SERS). First, in analogy to the electromagnetic SERS mechanism, near or between mirrors, the local field experienced by a molecule differ from that in vacuum. In particular, between mirrors, the cavity enhances the effective excited state population by trapping the EM field inside it. Second, the nearby metal surface provides a relaxation channel and a lineshape broadening mechanism, and inside a cavity this lineshape is inherited by the cavity polaritons. This relaxation results in a loss of yield but the associated broadening also leads to significant absorption over a larger frequency range. Third, near metallic interfaces interference between incident and reflected light can lead to a richly structured Raman spectrum. For instance, we find that the Rabi contraction (that results from depopulating the ground state) can interfere with Raman signals (and the effect appears to be the same order as Raman itself). These cavity effects are calculated by a full-scale FDTD simulation and highlight the convoluted but fascinating roles of photonic materials on optical signals.