Ultrafast Dynamics in Semiconductor Nanocavities with Deep Sub-Wavelength Confinement of Light

Optical microcavities [1] can significantly enhance light-matter interactions through spatial and spectral confinement, making them important for a variety of applications such as nanolasers, nonlinear photonics, and quantum optics. While traditional dielectric cavities offer strong spectral confinement, their spatial localization was thought to be governed by the so-called diffraction limit. In contrast, plasmonic cavities [2] are well-known to achieve sub-wavelength confinement but suffer from ohmic losses, which compromise their performance. Recently, dielectric bowtie cavities [3]–[4] have emerged as a promising alternative, combining ultrahigh quality factors with ultra-small mode volumes. These cavities enable deep sub-wavelength confinement, providing new possibilities for ultrafast and energy-efficient optical devices. Despite their great potential, the switching dynamics of these nanocavities remain unexplored experimentally. Here, we investigate the switching dynamics of a topology-optimized nanobeam bowtie cavity using the heterodyne pump-probe technique.