Fluctuations in photon local delay time and their relation to phase spectra in random media

TL;DR

This paper investigates the fluctuations in local delay times of microwave pulses transmitted through random media, revealing their relation to phase spectra and underlying mesoscopic dynamics.

Contribution

It introduces a detailed analysis of local delay time fluctuations and their connection to phase spectra in random dielectric samples, highlighting the role of phase singularities.

Findings

Large fluctuations in local delay time observed

Delay time distribution broadest near phase singularities

Delay time fluctuations reflect mesoscopic system dynamics

Abstract

The temporal evolution of microwave pulses transmitted through random dielectric samples is obtained from the Fourier transform of field spectra. Large fluctuations are found in the local or single channel delay time, which is the first temporal moment of the transmitted pulse at a point in the output speckle pattern. Both positive and negative values of local delay time are observed. The widest distribution is found at low intensity values near a phase singularity in the transmitted speckle pattern. In the limit of long duration, narrow-bandwidth incident pulses, the single channel delay time equals the spectral derivative of the phase of the transmitted field. Fluctuations of the phase of the transmitted field thus reflect the underlying statistics of dynamics in mesoscopic systems.