Extreme narrow band in Moir\'e Photonic time crystal

TL;DR

This paper introduces a novel Moiré photonic time crystal with superposed binary modulations, leading to extreme narrow bands and temporal localized modes, with potential applications in tunable mode-locked lasers.

Contribution

It extends photonic time crystal concepts to complex Moiré modulation patterns, revealing new wave manipulation capabilities in time-varying systems.

Findings

Extreme narrow bands in momentum space are achieved.

Temporal localized modes support periodically self-reconstructing pulses.

Mode-locking mechanisms enable tunable pulse widths.

Abstract

The Moir\'e superlattice has attracted growing interest in the electromagnetic and optical communities. Here, we extend this concept to time-varying photonic systems by superposing two binary modulations on the refractive index with different modulation periods, i.e., the Moir\'e photonic time crystal (PTC). Such a Moir\'e PTC leads to extreme narrow bands in momentum space which supports temporal localized modes, exhibiting periodically self-reconstructing pulse in time domain. We investigate how the modulation parameters change the bandstructure of the Moir\'e PTC and the temporal localization behavior. Moreover, we explore mode-locking mechanism in frequency space in the Moir\'e PTC, which points towards potential applications in mode-locked lasers with tunable time width of the emitted pulses. Our work therefore extends the study of PTC to complex modulation patterns, and unveils new possibility in wave manipulation with time-varying systems.