Time-resolved nonlinear microspectroscopy with Gaussian beams

Abstract

Time-resolved nonlinear microspectroscopy bridges high-resolution imaging and ultrafast spectroscopy, enabling the investigation of spatially localized molecular excited state and exciton dynamics on ultrafast timescales. By integrating ultrafast techniques such as pump–probe and coherent multidimensional spectroscopy with microscopy techniques utilizing high numerical aperture objective lenses and structured beams, these approaches provide label-free chemical contrast and reveal transient phenomena critical to understanding complex systems. Recent advancements, including adaptive optics and tailored beam profiles, have further enhanced spatial and temporal control, unlocking new possibilities for studying heterogeneous systems. This work explores time-resolved nonlinear microspectroscopy using Laguerre–Gaussian beams with orbital angular momentum. Analytical expressions for pump–probe microspectroscopy signals are derived to elucidate how beam parameters influence nonlinear responses reflecting spatial diffusion and ultrafast relaxation processes. The results demonstrate the potential of customized ultrafast pulses and spatial light fields to improve both resolution and sensitivity, advancing dynamic studies in materials science, chemistry, and biology.