The project comprises three principal work packages (WP1, WP3 and WP3) that represent the steps (i) formalisation and demonstration of the background concepts (ii) demonstration of the imaging approach and its features (iii) application of the imaging approach to challenging terahertz imaging scenarios.
WP1 completed the investigation on the nonlinear transformations relating the optical and THz patterns for sub-wavelength THz Computational Imaging
It is worth noting that parts of this development are now in progress for IP protection and resulted in the spin-out ERC-PoC project "THINK" for the exploitation of this IP.
WP2 completed the formalization and demonstration of the Time-Resolved Nonlinear Ghost Imaging .
WP3 Investigated Complex Media and superfocusing in the context of the Nonlinear Ghost Imaging.
The theoretical study about the deterministic and statistical approaches to boost imaging through a scattering media and gain spatiotemporal control of the scrambled light transmitted is completed. The experimental demonstration of deterministic wave control and imaging through scattering media is also completed.
Overview of the results and their exploitation and dissemination
The team explored the control of THz-patterned illumination using spatial light modulators and extended these findings to illumination patterns with delay distributions. The experimental foundation laid down, particularly the work on sub-wavelength illumination definition, demonstrated the feasibility of super-wavelength (space-time) and sub-wavelength imaging of samples in near-field coupling with a terahertz emitter. In the context of the experimental realisation, it explored suitable technologies for the generation and conditioning of Terahertz waves in the context of Terahertz Imaging, (Optica 4(11), 1358 (2017), IEEE Photon. Technol. Lett. 30(17), 1579–1582 (2018), Physical Review A 99(5), (2019), Sensors 22(23), 9432 (2022)). During the project implementation, the team also explored the physics of systems with reduced dimensionality (surfaces or quasi-2D materials) for their typical low thickness (high efficiency per unit of length), as the project determined the correlation between the thickness of the terahertz generators with the quality of near-field imaging (Nano Energy 46, 128–132 (2018), Micromachines 11(5), 521 (2020), Rev. Research 3(4), L042006 (2021), Phys. Rev. Lett. 125(26), 263901 (2020), Advanced Optical Materials 11(15), 2202578 (2023)).
The project delivered the theoretical and experimental foundation of the Nonlinear Ghost Imaging (ACS Photonics 5(8), 3379–3388 (2018)). The experimental campaigns demonstrated the operation of Nonlinear Ghost Imaging in real media and its performance against classical sources of noise (Optica 7(2), 186 (2020)) and the ability to perform microscopic THz tomographic images (ACS Photonics 10(6), 1726–1734 (2023))
The final stage of the project focused on generalizing Nonlinear Ghost Imaging for propagation in complex media. The theoretical and experimental demonstrations achieved spatiotemporal superfocusing, showing that a scattering medium could reshape the field with sub-wavelength spatial definition (Open Res Europe 2, 32 (2022), ACS Photonics 9(8), 2634–2642 (2022)). The culmination of this work is the ground-breaking demonstration of terahertz spatiotemporal wave synthesis exploiting disordered systems (ACS Photonics acsphotonics.3c01671 (2024)).
