Abstract-Hyperspectral terahertz microscopy via nonlinear ghost imaging

Luana Olivieri, Juan S. Totero Gongora, Luke Peters, Vittorio Cecconi, Antonio Cutrona, Jacob Tunesi, Robyn Tucker, Alessia Pasquazi, and Marco Peccianti

Conceptual description of the TNGI approach. (a) Key experimental components and methodology; (b) volumetric representation of the nonlinear generation of THz patterns; (c) fixed-time reconstruction with a field of view 2mm×2mm$2\mathrm{m}\mathrm{m}\times 2\mathrm{m}\mathrm{m}$ and 32×32$32\times 32$ spatial sampling; (d) backpropagated hyperspectral image, averaged between 1 and 2 THz.

https://www.osapublishing.org/optica/abstract.cfm?uri=optica-7-2-186

Ghost maging, based on single-pixel detection and multiple pattern illumination, is a crucial investigative tool in difficult-to-access wavelength regions. In the terahertz domain, where high-resolution imagers are mostly unavailable, ghost imaging is an optimal approach to embed the temporal dimension, creating a “hyperspectral” imager. In this framework, high resolution is mostly out of reach. Hence, it is particularly critical to developing practical approaches for microscopy. Here we experimentally demonstrate time-resolved nonlinear ghost imaging, a technique based on near-field, optical-to-terahertz nonlinear conversion and detection of illumination patterns. We show how space–time coupling affects near-field time-domain imaging, and we develop a complete methodology that overcomes fundamental systematic reconstruction issues. Our theoretical-experimental platform enables high-fidelity subwavelength imaging and carries relaxed constraints on the nonlinear generation crystal thickness. Our work establishes a rigorous framework to reconstruct hyperspectral images of complex samples inaccessible through standard fixed-time methods.

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