Terahertz Strong-Field Physics in Light-Emitting Diodes for Terahertz Detection and Imaging

TL;DR

This paper demonstrates that common LEDs can be used as fast, sensitive terahertz detectors and cameras by exploiting nonlinear effects induced by intense THz fields, opening new avenues for THz imaging and detection.

Contribution

It introduces a novel application of LEDs as high-responsivity, fast THz detectors and cameras based on nonlinear impact ionization and Schottky contact effects.

Findings

LEDs exhibit gigantic, fast photovoltaic signals under strong THz fields

Prototypes of THz-LED detectors and cameras achieve high responsivity (>1 kV/W)

Detection response time is shorter than pyroelectric detectors by four orders of magnitude

Abstract

Intense terahertz (THz) electromagnetic fields have been utilized to reveal a variety of extremely nonlinear optical effects in many materials through nonperturbative driving of elementary and collective excitations. However, such nonlinear photoresponses have not yet been discovered in light-emitting diodes (LEDs), letting alone employing them as fast, cost effective,compact, and room-temperature-operating THz detectors and cameras. Here we report ubiquitously available LEDs exhibited gigantic and fast photovoltaic signals with excellent signal-to-noise ratios when being illuminated by THz field strengths >50 kV/cm. We also successfully demonstrated THz-LED detectors and camera prototypes. These unorthodox THz detectors exhibited high responsivities (>1 kV/W) with response time shorter than those of pyroelectric detectors by four orders of magnitude. The detection mechanism was attributed to THz-field-induced nonlinear impact ionization and Schottky contact. These findings not only help deepen our understanding of strong THz field-matter interactions but also greatly contribute to the applications of strong-field THz diagnosis.