Enhanced infrared sensing with plasmonic metasurfaces and undetected light
File(s)
Author(s)
Severs Millard, Toby
Type
Thesis
Abstract
This thesis explores enhanced infrared sensing through nanophotonic manipulation of light and nonlinear interferometry, focusing on plasmonic metasurfaces and classical sensing with undetected light.
Motivated by overcoming limitations of conventional mid-infrared detection, nonlinear optical processes are used to transfer information from the infrared to visible for detection on silicon-based cameras. Through subwavelength confinement of electromagnetic fields, nanophotonic metasurfaces offer to extend the spectral range of bulk nonlinear materials and advance nonlinear interferometric technology. Here, plasmonic metasurfaces are employed as thin-film nonlinear sources of stimulated four-wave mixing and harmonic generation, respectively, within a Michelson interferometer. Pulsed illumination and bidirectional emission, due to the breakdown of out-of-plane phase matching restrictions, distinguishes thin-film interferometry from conventional operation. Utility of the information transfer is demonstrated by sensing through a silicon window, while detecting on a silicon-based camera. Phase sensitivity is observed to increase proportionally with harmonic order, an unprecedented feature of harmonic sensing with undetected light. Seeded interference is shown to be spatially single-mode in the far field; however, the broadened pulse facilitates spectrally resolved measurements.
As route to mid-infrared nonlinear metasurface sources, plasmonic dimer-coupled waveguide structures are optimised for nano-scale confinement to intensify light-matter interactions. The versatile design offers enhanced non-resonant sensing through parity-time symmetry as well as direct resonant coupling. Both approaches are investigated through integration of mid-infrared active molecule biphenyl-4-thiol, and further enhanced by the application complex-frequency wave analysis to artificially mitigate plasmonic losses. As biphenyl-4-thiol is known to coherently mix mid-infrared and visible frequencies, the metasurfaces are potential MIR nonlinear sources for sensing with undetected light.
Motivated by overcoming limitations of conventional mid-infrared detection, nonlinear optical processes are used to transfer information from the infrared to visible for detection on silicon-based cameras. Through subwavelength confinement of electromagnetic fields, nanophotonic metasurfaces offer to extend the spectral range of bulk nonlinear materials and advance nonlinear interferometric technology. Here, plasmonic metasurfaces are employed as thin-film nonlinear sources of stimulated four-wave mixing and harmonic generation, respectively, within a Michelson interferometer. Pulsed illumination and bidirectional emission, due to the breakdown of out-of-plane phase matching restrictions, distinguishes thin-film interferometry from conventional operation. Utility of the information transfer is demonstrated by sensing through a silicon window, while detecting on a silicon-based camera. Phase sensitivity is observed to increase proportionally with harmonic order, an unprecedented feature of harmonic sensing with undetected light. Seeded interference is shown to be spatially single-mode in the far field; however, the broadened pulse facilitates spectrally resolved measurements.
As route to mid-infrared nonlinear metasurface sources, plasmonic dimer-coupled waveguide structures are optimised for nano-scale confinement to intensify light-matter interactions. The versatile design offers enhanced non-resonant sensing through parity-time symmetry as well as direct resonant coupling. Both approaches are investigated through integration of mid-infrared active molecule biphenyl-4-thiol, and further enhanced by the application complex-frequency wave analysis to artificially mitigate plasmonic losses. As biphenyl-4-thiol is known to coherently mix mid-infrared and visible frequencies, the metasurfaces are potential MIR nonlinear sources for sensing with undetected light.
Version
Open Access
Date Issued
2025-06-17
Date Awarded
01/10/2025
License URL
Advisor
Oulton, Rupert
Phillips, Chris
Sponsor
National Physical Laboratory (Great Britain)
Engineering and Physical Sciences Research Council
UK Quantum Technology Hub in Quantum Enhanced Imaging (Great Britain)
Publisher Department
Department of Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)