Super-Resolution Orthogonal Deterministic Imaging Technique for Terahertz Subwavelength Microscopy

Abstract

Terahertz subwavelength imaging aims at developing THz microscopes able to resolve deeply subwavelength features. To beat the diffraction limit, the current trend is to use various subwavelength probes to convert the near-field to the far-field. These techniques offer significant gains in spatial resolution but suffer from low light throughput and are slow due to the necessity of a slow pixel-by-pixel raster scan. In parallel, in the visible spectral range, super-resolution imaging techniques enhance the image resolution by statistically correlating multiple frames of an object backlit by stochastically blinking fluorophores. In this work, we develop a super-resolution imaging technique for the THz range, that we name super-resolution orthogonal deterministic imaging (SODI). Since there are no natural THz fluorophores, we design artificial fluorophores in the form of optimal mask sets brought close to the object. By deterministically controlling the blinking, we avoid statistical averages and reconstruct high resolution images using very few frames. After developing the theoretical basis of SODI, we experimentally demonstrate the second-order resolution improvement using only eight phase and binary amplitude masks. We then show how to extend the SODI technique to higher orders to further improve the resolution. Our methodology can be readily adapted with existing THz phase-sensitive single-pixel imaging systems or any THz amplitude imaging arrays. Finally, this work can be of interest to the optical community in other wavelengths, as our technique can be used to deterministically structure light at a subwavelength scale in order to improve the image resolution with few frames and achieve real-time super-resolution microscopy.