arXiv subjects

John Guillamon

Publications and source records attributed to John Guillamon.

4 recordsLinked to original sources

arXiv2026

In-situ Adjoint Wave Control in Reconfigurable Non-Hermitian Nonlinear Systems

Complex multipath environments are usually avoided in wave-based information processing because repeated scattering creates many interfering propagation paths, obscuring controllability and generating extreme sensitivity to perturbations. The addition of nonlinear mechanisms fundamentally alters the wave-control landscape by breaking the superposition principle that underpins most wave-management strategies. Here, we show that these two apparent impediments -- multipath complexity and nonlinearity -- can instead be harnessed as key resources for physical optimization. We demonstrate an in-situ adjoint optimization protocol in a wave-chaotic platform incorporating a single localized nonlinear defect, in which the system itself performs both the forward and the adjoint propagations required for gradient evaluation. Recurrent multipath returns repeatedly expose the wave to the defect, producing from a minimal hardware a rich nonlinear input-output map with many pathway-mediated degrees of freedom. At the same time, a suitable adjoint excitation enables direct extraction of the sensitivities from measurements alone, without a digital twin or conventional numerical backpropagation. We experimentally validate the protocol on a minimal nonlinear multipath platform composed of incommensurate coaxial cables connected via T-junctions, one of which hosts a diode-loaded cavity. Our approach opens a route to adaptive wireless communications, imaging and analog intelligence in complex, partially unknown environments where conventional modeling is impractical.

physics.optics↗

arXiv2025

In-situ Physical Adjoint Computing in multiple-scattering electromagnetic environments for wave control

Controlling electromagnetic wave propagation in multiple scattering systems is a challenging endeavor due to the extraordinary sensitivity generated by strong multi-path contributions at any given location. Overcoming such complexity has emerged as a central research theme in recent years, motivated both by a wide range of applications -- from wireless communications and imaging to optical micromanipulations -- and by the fundamental principles underlying these efforts. Here, we show that an {\it in-situ} manipulation of the myriad scattering events, achieved through time- and energy-efficient adjoint optimization (AO) methodologies, enables {\it real time} wave-driven functionalities such as targeted channel emission, coherent perfect absorption, and camouflage. Our paradigm shift exploits the highly multi-path nature of these complex environments, where repeated wave-scattering dramatically amplifies small local AO-informed system variations. Our approach can be immediately applied to in-door wireless technologies and incorporated into diverse wave-based frameworks including imaging, power electronic and optical neural networks.

eess.SP↗

arXiv2025

Optimal Targeted Mode Transport in Complex Wave Environments: A Universal Statistical Framework

Recent advances in the field of structured waves have resulted in sophisticated coherent wavefront shaping schemes that provide unprecedented control of waves in various complex settings. These techniques exploit multiple scattering events and the resulting interference of wave paths within these complex environments. Here, we introduce the concept of targeted mode transport (TMT), which enables energy transfer from specific input channels to designated output channels in multimode wave-chaotic cavities by effectively engaging numerous cavity modes. We develop a statistical theory that provides upper bounds on optimal TMT, incorporating operational realities such as losses, coupling strengths and the accessibility of specific interrogating channels. The theoretical predictions for the probability distribution of TMT eigenvalues are validated through experiments with microwave chaotic networks of coaxial cables as well as two-dimensional and three-dimensional complex cavities. These findings have broad implications for applications ranging from indoor wireless communications to imaging and beyond.

physics.optics↗

arXiv2024

Nonlinearity-induced Scattering Zero Degeneracies for Spectral Management of Coherent Perfect Absorption in Complex Systems

We develop a Coherent Perfect Absorption (CPA) protocol for cases where scale invariance is violated due to the presence of nonlinear mechanisms. We demonstrate, using a microwave setting that lacks geometrical symmetries, that the nonlinearity offers new reconfigurable modalities: the destruction or formation of nonlinear CPAs (NL-CPAs), and their frequency positioning and bandwidth management using the incident power as a control knob. The latter occurs via the formation of exceptional point degeneracies of the zeroes of nonlinear scattering processes. Our results establish NL-CPA protocols as a versatile scheme for the creation of reconfigurable hot/cold-spots in complicated enclosures (e.g. buildings or vessels) with applications to next-generation telecommunications, long-range wireless power transfer, and electromagnetic warfare.

physics.optics↗