Tunable Narrowband Terahertz Radiation from van der Waals Ferroelectrics

TL;DR

This paper demonstrates tunable, narrowband terahertz radiation from ferroelectric van der Waals materials, with precise frequency control and electric field modulation, advancing integrated THz photonics for various technological applications.

Contribution

It introduces a new method for generating tunable, narrowband THz radiation using ferroelectric vdW materials with controllable emission frequencies and polarity.

Findings

Frequency tuning from 3.1 to 5.8 THz via halogen substitution and alloying.

Narrowband THz driven by phonons linked to ferroelectric polarization.

Electric field enables dynamic, nonvolatile control of THz wave polarity.

Abstract

The terahertz (THz) spectral range is central to high-speed communication, precision metrology, sensing technologies, and a range of fundamental scientific investigations. Achieving these capabilities in practical systems increasingly demands chip-scale integration of THz photonic components that are typically bulky. In this context, van der Waals (vdW) materials provide a unique platform for integrated nonlinear photonics in the visible and near-infrared regimes, and extending this framework into the THz domain would constitute a significant advance. Here, we report tunable, intense, and narrowband THz radiation from ferroelectric niobium oxyhalides. Through halogen substitution and alloying, we achieve continuous and precise control over the emission frequency from 3.1 to 5.8 THz. We show that the narrowband THz radiation is driven by phonons associated with the ferroelectric polarization. We further demonstrate dynamic and nonvolatile control of the polarity of the coherent THz wave with external electric field. This work demonstrates efficient narrowband THz emission from vdW ferroeletrics and provides microscopic insight into its origin, paving the way for on-chip THz technology for a broad range of applications.