Semiconductor microwave mirror for a measurement of the dynamical Casimir effect

TLDR

The dynamical Casimir effect predicts photon generation from a moving mirror, but has not been observed because it requires mirror vibrations at ~10⁹ Hz, which are technically infeasible. The study aims to realize a dynamical Casimir experiment by rapidly modulating a semiconductor’s reflectivity with pulsed laser light. The method uses laser‑illuminated semiconductor slabs to act as effective metallic mirrors, demonstrating that pulsed illumination can induce metallic reflectivity. Measurements on large silicon and GaAs samples confirm that laser illumination turns the semiconductor into a metal, validating the feasibility of the mirror‑modulation approach.

Abstract

According to QED a metallic mirror set in motion in quantum vacuum gives rise to “dissipated” energy in the form of real photons. This phenomenon, called dynamical Casimir effect, has never been observed due to unsolved technical difficulties: in order to obtain an experimentally measurable number of photons from vacuum fluctuations a reflecting surface has in fact to vibrate at very high frequencies (≃109 Hz). As these frequencies are too high to be achieved with a purely mechanical oscillation, our idea is to switch an effective microwave mirror on and off at very short intervals of time changing the reflectivity of a semiconductor layer by shining a pulsed laser beam on its surface. The first step to study the feasibility of this technique is to show that a semiconductor slab when illuminated by a laser behaves indeed as a metal. This article presents the measurements that confirm this demand, obtained by uniformly illuminating large (several square centimeters) surfaces of silicon and GaAs.