# Real-Time 0.89 THz Terahertz Imaging with High-Electron-Mobility Transistor Detector and Hydrogen Cyanide Laser for Non-Destructive Nut Detection

## TL;DR

Researchers developed a real-time terahertz imaging system using a hydrogen cyanide laser and a HEMT detector to inspect the internal structure of nuts non-destructively.

## Contribution

A novel real-time terahertz imaging system using HCN laser and HEMT detector for non-destructive nut inspection is introduced.

## Key findings

- The system achieved a lateral resolution of 2 mm for terahertz imaging.
- Terahertz imaging successfully revealed hidden structures inside nuts like pistachios and sunflower seeds.
- The technique can distinguish between full and unfilled nuts based on terahertz images.

## Abstract

We present a method for real-time terahertz imaging that employs a hydrogen cyanide (HCN) laser as a terahertz source at 0.89 THz and an AlGaN/GaN high-electron-mobility transistor (HEMT) terahertz detector as a camera. We developed an HCN laser and constructed a transmission imaging system based on it. This combination utilizes a high-power HCN laser with a highly sensitive terahertz detector, enabling practical applications of real-time terahertz imaging. A resolution test plane was produced to determine that the system could achieve a lateral resolution of 2 mm, and real-time terahertz imaging was carried out on Siemens star, pistachios, and sunflower seeds. The results demonstrate that the hidden structures inside nuts can be observed by terahertz imaging. Through our analysis of terahertz images of both sunflower seeds and pine nuts, we successfully assessed their fullness and demonstrated the capability to distinguish between full and unfilled nuts. These findings validate the potential of this technique for future applications in nut detection. We discuss the limitations of the current setup, potential improvements, and possible applications, and we outline the introduction of aspherical lenses and terahertz transmission tomography.