Efficient Terahertz detection in black-phosphorus nano-transistors with selective and controllable plasma-wave, bolometric and thermoelectric response

TLDR

Efficient, tunable conversion of light to electrical signals remains a key challenge in photonics, especially in the terahertz band where applications span high‑speed communications, security, and biomedical imaging. This work aims to create black‑phosphorus nano‑detectors that exploit in‑plane anisotropy to provide plasma‑wave, thermoelectric, and bolometric responses that can be selectively switched and controlled. The detectors are fabricated as room‑temperature, on‑chip devices coupled to planar nanoantennas that harvest terahertz radiation within a sub‑wavelength channel. They deliver 5–8 V W⁻¹ responsivity and a signal‑to‑noise ratio of 500, enabling real‑time terahertz imaging for pharmaceutical and quality‑control applications of large samples.

Abstract

The ability to convert light into an electrical signal with high efficiencies and controllable dynamics, is a major need in photonics and optoelectronics. In the Terahertz (THz) frequency range, with its exceptional application possibilities in high data rate wireless communications, security, night-vision, biomedical or video-imaging and gas sensing, detection technologies providing efficiency and sensitivity performances that can be "engineered" from scratch, remain elusive. Here, by exploiting the inherent electrical and thermal in-plane anisotropy of a flexible thin flake of black-phosphorus (BP), we devise plasma-wave, thermoelectric and bolometric nano-detectors with a selective, switchable and controllable operating mechanism. All devices operates at room-temperature and are integrated on-chip with planar nanoantennas, which provide remarkable efficiencies through light-harvesting in the strongly sub-wavelength device channel. The achieved selective detection (∼5-8 V/W responsivity) and sensitivity performances (signal-to-noise ratio of 500), are here exploited to demonstrate the first concrete application of a phosphorus-based active THz device, for pharmaceutical and quality control imaging of macroscopic samples, in real-time and in a realistic setting.