arXiv subjects

Rupert Oulton

Publications and source records attributed to Rupert Oulton.

6 recordsLinked to original sources

arXiv2026

Wide-field mid- to long-wave infrared imaging with undetected photons

Quantum imaging with undetected photons (QIUP) allows an object to be probed at mid-infrared frequencies by only measuring interference in the visible range, thus leveraging silicon camera technology. We show that non-collinear phase-matching in a silver thiogallate (AgGaS$_2$) crystal enables wide-field QIUP in the wavelength range of 6-10 $\mu$m (1670-1000 cm$^{-1}$). A combination of coherent detection and infrared photons being ``undetected'' enables imaging at ${\sim}$100 times better than the background-limited infrared photodetection (BLIP) limit. At 8 $\mu$m, our images have over 8000 $\pm$ 100 resolvable elements with a 297 $\pm$ 5 $\mu$m resolution, and 10 s acquisition time. Our results pave the way to fast, background-noise-free, room-temperature, spectrally-selective mid-infrared imaging.

quant-ph↗

arXiv2025

Photon Bose-Einstein Condensation in Semiconductors: A Quantum Kinetic Theory

Photon condensation in semiconductor microcavities is a transformative technique for engineering quantum states of light at room temperature by tailoring strong but incoherent light-matter interactions. While continuous-wave and electrical pumping offer exceptional prospects for miniaturized quantum photonic technologies, harnessing these requires conceptual advances in understanding nonequilibrium light-matter dynamics in semiconductors. We resolve this challenge through an \textit{ab initio} quantum kinetic theory capturing how Coulomb interactions of optically excited carriers and phonon scattering mediate photon thermalization and condensation in semiconductors. Our microscopic model shows that at high carrier densities, thermalization is dominated by carrier-carrier Coulomb scattering, in clear contrast to the rovibrational relaxation that governs dye-based photon condensates. The theory predicts a rich nonequilibrium phase diagram with thermal, Bose-condensed, multimode, and lasing phases, quantitatively in agreement with recent experiments. Crucially, we identify how cavity detuning controls transitions between equilibrium and gain-dominated regimes, enabling tailored design of coherent light sources. This work thus provides the foundation for semiconductor-based quantum photonic devices operating beyond conventional laser paradigms.

physics.optics↗

arXiv2025

Optical and electrical probing of plasmonic metal-molecule interactions

Plasmonic nanostructures enable efficient light-to-energy conversion by concentrating optical energy into nanoscale volumes. A key mechanism in this process is chemical interface damping (CID), where surface plasmons are damped by adsorbed molecules, enabling the transfer of charge to adsorbed molecules. In this study, we investigate the relationship between CID and adsorbate-induced changes in DC electrical resistivity for four molecular adsorbates-adenine, 4-aminothiophenol (ATP), biphenyl thiol (BPT), and 1-dodecanethiol (DDT)-on gold surfaces. Our results reveal two distinct CID regimes. BPT causes CID via direct electronic transitions to the lowest unoccupied molecular orbital (LUMO), which is centered at approx. 2 eV above the Fermi level and can be resonantly excited by the plasmon. This mechanism is dependent on plasmon energy. In contrast, ATP, adenine and DDT lead to plasmon damping through inelastic electron scattering at the metal-molecule interface. This regime shows a weaker dependency on plasmon energy since it does not involve resonant electron excitation between hybridized metal-molecule states. This same mechanism contributes to adsorbate-induced changes in DC resistivity, suggesting that resistivity measurements can serve as a probe of plasmonic energy transfer, as highlighted by the good correlation between the two effects. These findings provide new insights into the microscopic origins of plasmon damping and offer a unified framework for understanding metal-adsorbate energy transfer.

physics.optics↗

arXiv2024

Surface lattice resonance lasers with epitaxial InP gain medium

Surface lattice resonance (SLR) lasers, where gain is supplied by a thin film active material and the feedback comes from multiple scattering by plasmonic nanoparticles, have shown both low threshold lasing and tunability of the angular and spectral emission. However, typically used materials such as organic dyes and QD films suffer from photo-degradation which hampers practical applications. Here, we demonstrate photo-stable single-mode lasing of SLR modes sustained in an epitaxial solid-state InP slab waveguide. The nanoparticle array is weakly coupled to the optical modes, which decreases the scattering losses and hence the experimental lasing threshold is as low as 90 $\mu$J/cm$^{2}$. The nanoparticle periodicity defines the lasing wavelength and enables tuneable emission wavelengths over a 70 nm spectral range. Combining plasmonic nanoparticles with an epitaxial solid-state gain medium paves the way for large-area on-chip integrated SLR lasers for applications including optical communication, optical computing, sensing, and LiDAR.

physics.optics↗

arXiv2023

Ultrastrong magnon-magnon coupling and chiral spin-texture control in a dipolar 3D multilayered artificial spin-vortex ice

Strongly-interacting nanomagnetic arrays are ideal systems for exploring reconfigurable magnonics. They provide huge microstate spaces and integrated solutions for storage and neuromorphic computing alongside GHz functionality. These systems may be broadly assessed by their range of reliably accessible states and the strength of magnon coupling phenomena and nonlinearities. Increasingly, nanomagnetic systems are expanding into three-dimensional architectures. This has enhanced the range of available magnetic microstates and functional behaviours, but engineering control over 3D states and dynamics remains challenging. Here, we introduce a 3D magnonic metamaterial composed from multilayered artificial spin ice nanoarrays. Comprising two magnetic layers separated by a non-magnetic spacer, each nanoisland may assume four macrospin or vortex states per magnetic layer. This creates a system with a rich $16^N$ microstate space and intense static and dynamic dipolar magnetic coupling. The system exhibits a broad range of emergent phenomena driven by the strong inter-layer dipolar interaction, including ultrastrong magnon-magnon coupling with normalised coupling rates of $\frac{\Delta \omega}{\gamma} = 0.57$, GHz mode shifts in zero applied field and chirality-selective magneto-toroidal microstate programming and corresponding magnonic spectral control.

cond-mat.mes-hall↗

arXiv2023

Eliminating Thermal IR Background Noise by Imaging with Undetected Photons

Spectroscopy and imaging in the mid-infrared (2.5 $\mu$m $\sim$ $\lambda$ $\sim$ 25 $\mu$m) is bedevilled by the presence of a strong 300 K thermal background at room temperature that makes IR detectors decades noisier than can be readily achieved in the visible. The technique of "imaging with undetected photons" (IUP) exploits the quantum correlations between entangled photon pairs to transfer image information from one spectral region to another, and here we show that it does so in a way that is immune to the thermal background. This means that IUP can be used to perform high speed photon counting measurements across the mid-IR, using uncooled visible detectors that are many times cheaper, faster, and more sensitive than their IR counterparts.

quant-ph↗