Detectorless 3D terahertz imaging: achieving subwavelength resolution with reflectance confocal interferometric microscopy

Jorge Silva; Martin Plöschner; Karl Bertling; Mukund Ghantala; Tim Gillespie; Jari Torniainen; Jeremy Herbert; Yah Leng Lim; Thomas Taimre; Xiaoqiong Qi; Bogdan C. Donose; Tao Zhou; Hoi-Shun Lui; Dragan Indjin; Yingjun Han; Lianhe Li; Alexander Valavanis; Edmund H. Linfield; A. Giles Davies; Paul Dean; Aleksandar D. Rakić

arXiv · 2412.18403

Detectorless 3D terahertz imaging: achieving subwavelength resolution with reflectance confocal interferometric microscopy

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Abstract

Terahertz imaging holds great potential for non-destructive material inspection, but practical implementation has been limited by resolution constraints. In this study, we present a single-pixel THz imaging system based on a confocal microscope architecture, utilising a quantum cascade laser as both transmitter and phase-sensitive receiver. Our approach integrates laser feedback interferometry detection to achieve a two-fold improvement in lateral resolution and a two-order-of-magnitude enhancement in axial resolution over conventional imaging through precise interferometric phase measurements. This translates to a lateral resolution near $\lambda/2$ and a depth of focus better than $\lambda/5$, significantly outperforming traditional confocal systems. The system can produce a 0.5 Mpixel image in under two minutes, surpassing both raster-scanning single-pixel and multipixel focal-plane array-based imagers. Coherent operation enables simultaneous amplitude and phase image acquisition, and a custom visualisation method links amplitude to image saturation and phase to hue, enhancing material characterisation. A 3D tomographic analysis of a silicon chip reveals subwavelength features, demonstrating the system's potential for high-resolution THz imaging and material analysis. This work sets a new benchmark for THz imaging, overcoming key challenges and opening up transformative possibilities for non-destructive material inspection and characterisation.

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Jorge Silva, Martin Plöschner, Karl Bertling, Mukund Ghantala, Tim Gillespie, Jari Torniainen, Jeremy Herbert, Yah Leng Lim, Thomas Taimre, Xiaoqiong Qi, Bogdan C. Donose, Tao Zhou, Hoi-Shun Lui, Dragan Indjin, Yingjun Han, Lianhe Li, Alexander Valavanis, Edmund H. Linfield, A. Giles Davies, Paul Dean, Aleksandar D. Rakić. 2024-12-24. Detectorless 3D terahertz imaging: achieving subwavelength resolution with reflectance confocal interferometric microscopy. https://arxiv.org/abs/2412.18403

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