arXiv subjects

Cade Peters

Publications and source records attributed to Cade Peters.

11 recordsLinked to original sources

arXiv2026

Real-time estimation of the transmission matrix of an atmospheric channel

Optical wavelengths have received significant attention in free-space channels and are vital for applications in communications, imaging and sensing. Their widespread implementation is motivated by a variety of factors including improved bandwidths, increased security and higher energy efficiency. However, these advantages cannot be fully brought to bear in real-world scenarios due to the deleterious effects of atmospheric turbulence. Induced by small temperature and pressure fluctuations in the environment that vary rapidly in space and time, these effects cause significant power losses which decrease SNR, induce severe crosstalk in communication links, and greatly limit resolution of long-range imaging systems. To overcome this, we numerically and experimentally investigate the reconstruction of the transmission matrix of a time-evolving atmospheric channel with a real-time recursive optimization routine. We demonstrate that this estimation technique is able to keep up with the evolution of the channel and enables a significant improvement of communication-relevant quantities such as the coupling of the received light into a single-mode fiber while notably reducing the probability and duration of power outages, even in strong turbulence. Our results have immediate applications in free-space optical communication in both the classical and quantum regimes.

physics.optics↗

arXiv2026

Towards digital phantoms: emulating scattering with a spatial light modulator

The distortion of light's degrees of freedom when passing through complex random media is of great interest across a diversity of fields, e.g., scattering in biological studies. Emulating such media in a controlled laboratory setting conventionally relies on real-world physical samples (e.g., white paint), inhomogeneous mixtures with embedded scatterers, or biological tissue-mimicking phantoms. Such methods, while effective in certain contexts, are not without complexity and limitations: the exact medium properties are challenging to control and often require laborious preparation, external characterisation techniques, are not easily reproducible between studies and cannot be matched precisely by numerical simulations. Here, we propose a simple all-digital implementation of random scattering which can be readily implemented on any setup capable of producing digital holograms. Our approach employs binary random phase masks encoded onto a spatial light modulator which perturbs the input beam's phase and amplitude. We highlight two methods to precisely tune distortion strengths which show excellent agreement between simulated and measured results. We demonstrate distortion strengths comparable to real-world scattering samples and illustrate two example applications to emulate scattering of scalar and vectorial structured light. Finally we showcase the versatility of this toolkit for emulating various amplitude and phase profiles and suggest several easy to implement alternative modalities accessible with this method. This digital phantom circumvents many of the practical challenges of physical samples, making it ideally suited for applications at the intersection of structured light, biological imaging and optical communications.

physics.optics↗

arXiv2026

Topological robustness of orbital angular momentum entanglement in stochastic channels

Orbital angular momentum (OAM) entanglement gives access to multiple qubit and high dimensional Hilbert spaces, but is unfortunately susceptible to disturbance, decaying in real-world noisy channels. Here, we show there is an underlying topology arising from OAM entanglement that is robust to such channels, which we demonstrate using atmospheric turbulence -- exemplary of stochastic or chaotic media. Using a quantum channel with various turbulence strengths, we find the OAM topological observable preserved even though the OAM itself is shown to be highly sensitive to the turbulence. We show this is true for mixed states too, with the OAM topology intact even as the purity of the state decreases due to decoherence. Our work offers a new perspective on OAM entanglement preservation, and may easily be extended to other spatial bases, degrees of freedom, as well as complex channels, whether static or dynamic.

quant-ph↗

arXiv2026

Particle-like topologies of light in turbulent complex media

The basic building blocks of many forms of optical topologies are particle-like singularities in phase and polarisation, giving rise to lines of darkness that weave complex threads in 3D space. Although known for half a century since seminal work on dislocations in wave trains, their behaviour in complex media remains under debate, especially with respect to their relative stability. Here we show that polarisation and phase vortices behave identically in one-sided turbulent complex channels. We perform complementary numerical and experimental studies using atmospheric turbulence as a test case, demonstrating agreement and equivalent dynamics. Our work addresses open questions on optical topologies and will be relevant to their harnessing for applications such as sensing, communication, imaging, and information transfer in noisy or complex environments.

physics.optics↗

arXiv2026

Topological robustness of optical skyrmions through a real-world free-space link

Structured light offers a promising solution for the increasing data demands of modern optical networks, opening up new degrees of freedom that can be leveraged for greater channel capacity and more bits per photon. However, its implementation is hindered by real-world distortions, for example, atmospheric turbulence in free-space, with severe and rapidly evolving phase perturbations that alter the amplitude, phase and vectorial polarization structure of the beam. Here, we demonstrate that optical topologies in the form of skyrmions are highly resilient to the effects of real-world atmospheric turbulence. We create and transmit these particle-like topologies of light through a 270~m free-space optical link, revealing their robustness across a wide variety of conditions and turbulence strengths. While we observe severe distortion in the states' underlying degrees of freedom, we show that the topological numbers are preserved in all cases. We account for fast changes to the medium, where the channel produces statistically averaged outcomes, by probing the state's decoherence, showing that while the degree of polarisation consequently decays, the topology remains intact. Using topology, we show information can be transmitted through the channel with almost perfect fidelity (>98%) in most cases, only decreasing to 86% in the most severe conditions tested. Our work is the first to demonstrate the potential for optical topologies as reliable and robust information carriers in a real-world environment and points to the potential for other complex channels too, offering attractive features for classical and quantum communication alike.

physics.optics↗

arXiv2025

Deep diffractive optical neural networks for detecting Skyrmionic topologies of light

Optical Skyrmions are topological forms of structured light with the potential of an infinite encoding alphabet that is immune to disturbance. This attractive prospect is hindered by the lack of any topological detector, a challenging problem due to the non-orthogonal nature of the topological invariant (N). Here we demonstrate the first deterministic detector for Skyrmionic topologies of light using a deep diffractive optical neural network. Our network uses two independent processing channels of 5 diffractive layers each to map incoming topologies to spatially separated Gaussian channels from which N can be detected. We overcome the complexity of the training by using a spatial mode basis rather than pixels, reducing the training variables by x1000 compared to current methods. We use the detector on an input set of 81 input topologies, showing high accuracy even in the presence of significant levels of noise. Finally, to show the practical utility of the device, we transmit and receive an image encoded in a 14-level topological alphabet with no discernible cross-talk. Our work offers a new paradigm for the emergent field of diffractive optical networks and can easily be extended to other forms of optical topologies, setting a clear pathway for their deployment in real-world applications.

physics.optics↗

arXiv2025

Topological robustness of classical and quantum optical skyrmions in atmospheric turbulence

The degradation of classical and quantum structured light induced by complex media constitutes a critical barrier to its practical implementation in a range of applications, from communication and energy transport to imaging and sensing. Atmospheric turbulence is an exemplary case due to its complex phase structure and dynamic variations, driving the need to find invariances in light. Here we construct classical and quantum optical skyrmions and pass them through experimentally simulated atmospheric turbulence, revealing the embedded topological resilience of their structure. In the quantum realm, we show that while skyrmions undergo diminished entanglement, their topological characteristics maintain stable. This is paralleled classically, where the vectorial structure is scrambled by the medium yet the skyrmion remains stable by virtue of its intrinsic topological protection mechanism. Our experimental results are supported by rigorous analytical and numerical modelling, validating that the quantum-classical equivalence of the topological behaviour is due to the non-separability of the states and one-sided nature of the channel. Our work blurs the classical-quantum divide in the context of topology and opens a new path to information resilience in noisy channels, such as terrestrial and satellite-to-ground communication networks.

physics.optics↗

arXiv2025

Seeing through randomness with topological light

Transmitting structured light robustly through complex random media is crucial in many applications, from sensing to communication. Unfortunately, the spatial structure of light is distorted in such media due to refractive index inhomogeneities that cause multiple scattering, requiring mitigating strategies such as iterative optimisation and adaptive optics. Here, we use topological light to see through random media without the need for any corrective measures. Using skyrmions as our optical topology, we first demonstrate their robustness to randomness using controlled digital random phase masks before showing the universality of the approach with physical samples, from biological tissue to highly scattering materials. We benchmark the invariance of the topology against orbital angular momentum (OAM) and show no modal crosstalk using topology in channels where orbital angular momentum exhibits crosstalk greater than 70%. With the control in hand, we transmit images encoded into an alphabet of 10 topological numbers and show information transfer with high fidelity in regimes where traditional degrees of freedom, such as OAM, fail. Our work represents an important step towards noise-free transmission through noisy channels with the spatial structure of light without the need for active compensation strategies, opening potential applications in imaging, sensing and communicating with topology.

physics.optics↗

arXiv2025

Disorder-enabled Synthetic Metasurfaces

Optical metasurfaces have catalyzed transformative advances across imaging, optoelectronics, quantum information processing, sensing, energy conversion, and optical computing. Yet, despite this rapid progress, most research remains focused on optimizing single functionalities, constrained by the persistent challenge of integrating multiple functions within a single device. Here, we demonstrate that engineered structural disorder of metapixels, used to implement a photonic function, can significantly reduce the area required across the entire aperture without compromising optical performance. The unallocated space can then be repurposed to encode functionally distinct metapixels without increasing the design complexity, each independently addressable via various optical degrees of freedom. As a proof of concept, we present a synthetic achromatic metalens featuring 11 spectrally distinct lens profiles encoded through nonlocal metapixels engineered to support sharp resonances via quasi bound states in the continuum. This large-scale metalens with 8.1 mm aperture achieves diffraction-limited achromatic focusing across the 1200 to 1400 nm spectral window. We further incorporate polarization-selective metapixels to implement momentum-space distinct gratings, enabling single-shot, high spatial resolution polarimetric imaging of arbitrarily structured light fields, including radial and azimuthal vector beams and optical skyrmions. Altogether, this disorder-enabled synthetic metasurface platform establishes a versatile foundation for unifying diverse photonic functionalities within a single optical element, marking a substantial step toward compact, high-density, multifunctional optical devices.

physics.optics↗

arXiv2025

Tailoring light to create invariant modal spectra through complex channels

Light's spatial degree of freedom is emerging as a potential resource for a myriad of applications, in both classical and quantum domains, including secure communication, sensing and imaging. However, it has been repeatedly shown that a complex medium (atmosphere, optical fibre, turbid media, etc.) can perturb the spatial amplitude, phase and polarization of the structured light fields leading to a degradation in their performance. A promising solution to this is the use of invariant modes to whom the medium appears transparent. While the creation and robustness of these modes has been experimentally demonstrated, they are difficult to implement in many important applications due to large channel matrices, a susceptibility to numerical artefacts, non-physical solutions and unreliable performance. In this work, we outline a procedure for determining these invariant modes using a modal basis, which results in a set of eigenmodes that are free of these issues, are consistently realisable and require a much smaller channel matrix to compute. Using atmospheric turbulence and LG modes as the underlying basis as an illustrative example, we find robust modes for a variety of turbulence strengths with a basis of only 231 modes, one order of magnitude smaller than previous approaches. These modes consistently show a fidelity of above 80% after propagating through the complex channel, a significant improvement over sending the individual LG modes themselves and reveal an invariant modal spectrum through the channel. Our approach will work for any complex medium and modal basis, paving the way for the effective implementation of the eigenmode approach in real-world situations.

physics.optics↗

arXiv2022

Robust structured light in atmospheric turbulence

Structured light is routinely used in free space optical communication channels, both classical and quantum, where information is encoded in the spatial structure of the mode for increased bandwidth. Unlike polarisation, the spatial structure of light is perturbed through such channels by atmospheric turbulence, and consequently, much attention has focused on whether one mode type is more robust than another, but with seemingly inconclusive and contradictory results. Both real-world and experimentally simulated turbulence conditions have revealed that free-space structured light modes are perturbed in some manner by turbulence, resulting in both amplitude and phase distortions. Here, we present complex forms of structured light which are invariant under propagation through the atmosphere: the true eigenmodes of atmospheric turbulence. We provide a theoretical procedure for obtaining these eigenmodes and confirm their invariance both numerically and experimentally. Although we have demonstrated the approach on atmospheric turbulence, its generality allows it to be extended to other channels too, such as underwater and in optical fibre.

physics.optics↗