Smith-Purcell radiation from time grating

TL;DR

This paper introduces temporal Smith-Purcell radiation (t-SPR), a novel form of light emission from electrons interacting with a time-modulated system, offering enhanced control and robustness over traditional SPR.

Contribution

The paper proposes a generalized dispersion equation for t-SPR and demonstrates its advantages over conventional SPR, including greater manipulation, robustness, and energy amplification.

Findings

t-SPR can be manipulated via temporal modulation parameters.

t-SPR shows robustness to electron-grating separation.

Temporal modulation introduces additional energy channels, amplifying emission.

Abstract

Smith-Purcell radiation (SPR) occurs when an electron skims above a spatial grating, but the fixed momentum compensation from the static grating imposes limitations on the emission wavelength. It has been discovered that a temporally periodic system can provide energy compensation to generate light emissions in free space. Here, we introduce temporal SPR (t-SPR) emerging from a time grating and propose a generalized t-SPR dispersion equation to predict the relationship between radiation frequency, direction, electron velocity, modulation period, and harmonic orders. Compared to conventional SPR, t-SPR can: 1) Provide a versatile platform for manipulating SPR emission through temporal modulation (e.g., period, amplitude, wave shape). 2) Exhibit strong robustness to the electron-grating separation, alleviating the constraints associated with extreme electron near-field excitation. 3) Introduce additional energy channels through temporal modulation, enhancing and amplifying emission.