Effects due to generation of negative frequencies during temporal diffraction

TL;DR

This paper demonstrates how rapid temporal modulation using graphene in the THz range can generate a broad spectrum of frequencies, including negative ones, leading to distinctive interference effects in the transmitted spectrum.

Contribution

It presents the first experimental demonstration of negative frequency generation during temporal diffraction in the THz domain using graphene.

Findings

Significant modulation faster than the THz field period achieved.

Generation of a broad bandwidth including negative frequencies.

Interference effects cause oscillatory features in the spectrum.

Abstract

Temporal diffraction from rapidly time-modulated materials can generate new frequency components not present in an incident wave. In such an experiment, the spectral extent of these new frequencies is determined by the rate of modulation relative to the period of the oscillating field. Here we present a temporal diffraction experiment carried out in the far-infrared (THz) spectral region. Using graphene, a fast modulator for this spectral domain, we show that one can modulate the transmission significantly faster than the period of a narrow band THz field. This leads to a large bandwidth for the generated frequencies, including the generation of negative frequency components. We show that interference between negative and positive frequency components give rise to distinctive oscillatory features in the transmitted spectrum.