Frozen Surface Modes on a Moving Interface

TL;DR

This paper investigates frozen surface modes caused by group-velocity matching on moving interfaces, leading to enhanced light-matter interactions and resonant energy accumulation.

Contribution

It introduces the concept of frozen surface modes in dispersive systems where group velocity matches emitter velocity, a novel regime for light-matter interaction.

Findings

Resonant energy accumulation occurs at the interface.

Local density of optical states is significantly increased.

Optomechanical forces and torques are enhanced.

Abstract

Spatio-temporal modulation enables synthetic motion at effective velocities approaching the speed of light, providing new regimes for light-matter interaction. Traditional Cherenkov-type effects arise when the velocity of an emitter matches or exceeds the phase velocity of electromagnetic modes supported by a medium. Here, we study dispersive systems in which phase and group velocities differ markedly. Specifically, we explore the case of group-velocity matching for surface waves, where the emitter moves at the same velocity as the flow of energy. This gives rise to frozen surface modes which are stationary in the emitter frame, accompanied by resonant energy accumulation. The result is a dramatic increase of the local density of optical states, the power extracted from the emitter, and the optomechanical forces and torques it experiences. Since surface modes naturally exhibit slow group velocities, this is accessible at lower relative speeds than phase-velocity effects. This phenomenon provides a route to enhanced light-matter interaction via real or synthetic motion.