arXiv subjects

Rosanna Mastria

Publications and source records attributed to Rosanna Mastria.

7 recordsLinked to original sources

arXiv2026

Compact Variational Neural Networks for Spectral Inference from a Single Nonlinear 2D Perovskite Photodetector

Spectroscopy conventionally separates optical frequencies before detection, imposing persistent constraints on footprint, complexity and scalability. Here we establish an alternative paradigm in which the nonlinear optoelectronic dynamics of a single two-dimensional perovskite photodetector physically encode the incident optical field and machine learning performs the inverse spectral reconstruction. Using a planar fluorinated phenethylammonium lead iodide (F-PEAI) photodetector, we exploit wavelength- and irradiance-dependent current-voltage signatures arising from the coupled effects of photocarrier generation, trapping, interfacial transport and field-dependent carrier dynamics. A compact variational encoder-decoder preserves the functional and history-dependent structure of these responses by independently projecting forward and reverse voltage sweeps onto a truncated Legendre-polynomial basis before mapping them through a probabilistic latent representation to continuous spectral parameters. Trained on fewer than 400 experimental voltage sweeps, the model generalises to excitation wavelengths excluded from training, reconstructing wavelength with $R^2=0.958$ and a mean absolute error of 8.1 nm, while recovering log-normalised irradiance with $R^2=0.987$. Voltage-resolved analysis further reveals that wavelength and irradiance are encoded differently across the nonlinear device response, with distinct bias regions carrying complementary optical information. These results establish nonlinear material and interface dynamics as a computational resource for spectroscopy and point towards hardware-algorithm co-design in which materials, interfaces and inference architectures are engineered jointly to maximise information content, enabling compact spectroscopic systems without dispersive optics or detector arrays.

physics.optics↗

arXiv2025

Fully Integrated Perovskite Polaritonic Circuits with Tunable Lasing and Nonlinear Amplification

Photonic integrated circuits are emerging as a key technology for compact and energy-efficient optical information processing. Yet, their practical implementation remains limited by the intrinsically weak optical nonlinearities of conventional materials, which demand high power and large footprints to achieve significant nonlinear responses. Exciton-polaritons, hybrid light-matter excitations of semiconducting materials, offer a promising solution by combining strong optical nonlinearities with the high speed and large scalability typical of photonic devices. However, despite their potential, working on-chip polaritonic elements demonstrating room temperature coherent lasing, controllable nonlinear propagation, or amplification have remained elusive. Here we demonstrate a fully integrated perovskite polaritonic circuit that overcomes these limitations. Using a single-step microfluidic lithographic technique, we realize waveguide circuits with integrated gratings that simultaneously act as couplers and mirrors, forming in-plane Fabry-Pérot cavities. These structures support robust in-plane polariton lasing between gratings, yielding coherent emission along the waveguide. Furthermore, we observe clear signatures of strong nonlinear self-phase modulation and, for the first time, optical amplification of guided polaritons at room temperature. Our simple, scalable platform opens the way to low-power, highly nonlinear optical circuits for integrated photonics and neuromorphic architectures operating at room temperature.

physics.optics↗

arXiv2025

Microfluidic-Assisted Growth of Perovskite Microwires for Room-Temperature All-Optical Switching Based on Total Internal Reflection

The development of efficient integrated photonic circuits is fundamental for ongoing research in information processing and computer science. The greatest challenge in strong light-matter regime facing photonic systems is achieving strong nonlinearities, which are exploitable in strongly coupled systems, leading to the formation of exciton-polaritons. In this context, the use of hybrid organic-inorganic perovskites offers a promising alternative, exhibiting robust interactions at Room Temperature (RT). However, the development of perovskite-based integrated devices requires both the ability to achieve long in-plane propagation, and the development of alternative fabrication approaches tailored to perovskite materials, designed to preserve their optical properties and prevent degradation. Herein, we present the realization of a proof-of-concept all-optical switch using propagating polaritons confined in Total Internal Reflection (TIR), which ensures long in-plane propagation and limited optical losses. We realized an efficient injection/extraction of the TIR-confined waveguide polariton modes by employing gold grating couplers prepatterned on the substrate.

physics.optics↗

arXiv2024

Enhanced polariton interactions in suspended WS2 monolayer microcavity

Transition-metal dichalcogenides monolayers exhibit strong exciton resonances that enable intense light-matter interactions at room temperature (RT). However, the sensitivity of these materials to the surrounding environment and their intense interactions with the sustaining substrate result in the enhancement of excitonic losses through scattering, dissociation and defects formation, hindering their full potential for the excitation of optical nonlinearities in exciton-polariton platforms. From this point of view, the use of suspended monolayers holds the potential to completely eliminate substrate-induced losses, offering unique advantages for the investigation and exploitation of intrinsic electronic, mechanical, and optical properties of 2D materials based polaritonic systems, without any influence of proximity effects of all sort. In this work, we report a novel fabrication approach enabling the realization of a planar λ/2 microcavity filled with a suspended WS2 monolayer in its centre. In such a system, we experimentally demonstrate a 2-fold enhancement of the strong coupling at RT, due to reduced overall losses as compared to similar systems based on dielectric-filled microcavities. Moreover, as a result of minimized losses, spin-dependent polaritonic interactions in our platform are significantly amplified, leading to achievement of a record exciton interaction constant approaching the theoretically predicted value at RT, without making use of theoretical hypothesis on the effective polariton densities. This approach holds promises for pushing 2D materials-based polaritonic systems to their intrinsic limits, paving the way for the realization of novel polaritonic devices with superior performance.

physics.optics↗

arXiv2023

Room temperature polariton condensation from Whispering gallery modes in CsPbBr3 microplatelets

Room temperature (RT) polariton condensate holds exceptional promise for revolutionizing various fields of science and technology, encompassing optoelectronics devices to quantum information processing. Using perovskite materials like all-inorganic CsPbBr3 single crystal provides additional advantages, such as ease of synthesis, cost-effectiveness, and compatibility with existing semiconductor technologies. In this work, we show the formation of whispering gallery modes (WGM) in CsPbBr3 single crystals with controlled geometry, synthesized using a lowcost and efficient capillary bridge method. Through the implementation of microplatelets geometry, we achieve enhanced optical properties and performance thanks to the presence of sharp edges and a uniform surface, effectively avoiding non-radiative scattering losses caused by defects. This allows us not only to observe strong light matter coupling and formation of whispering gallery polaritons, but also to demonstrate the onset of polariton condensation at RT. This investigation not only contributes to the advancement of our knowledge concerning the exceptional optical properties of perovskite-based polariton systems, but also unveils prospects for the exploration of WGM polariton condensation within the framework of a 3D perovskite-based platform, working at RT. The unique characteristics of polariton condensate, including low excitation thresholds and ultrafast dynamics, open up unique opportunities for advancements in photonics and optoelectronics devices.

physics.optics↗

arXiv2023

Engineering Dion-Jacobson Perovskites in Polariton Waveguides

Hybrid two-dimensional perovskites hold considerable promise as semiconductors for a wide range of optoelectronic applications. Many efforts are addressed to exploit the potential of these materials by tailoring their characteristics. In this work, the optical properties and electronic band structure in three new Dion-Jacobson (DJ) perovskites (PVKs) are engineered by modulating their structural distortion. Two different interlayer cations: 1-6, Hexamethylendiammonium, HE, and 3-(Dimethylamino)-1-propylammonium, DMPA, have been selected to investigate the role of the cation length and the ammonium binding group on the crystalline structure. This study provides new insights into the understanding of the structure-property relationship in DJ perovskites and demonstrates that exciton characteristics can be easily modulated with the judicious design of the organic cations. DJ PVKs developed in this work were also grown as size-controlled single crystal microwires through a microfluidic-assisted synthesis technique and integrated in a nanophotonic device. The DJ PVK microwire acts as a waveguide exhibiting strong light-matter coupling between the crystal optical modes and DJ PVK exciton. Through the investigation of these polariton waveguides, the nature of the double peak emission, which is often observed in these materials and whose nature is largely debated in the literature, is demonstrated originating from the hybrid polariton state.

cond-mat.mtrl-sci↗

arXiv2015

Molecular-Level Switching of Polymer/Nanocrystal Non-Covalent Interactions and Application in Hybrid Solar Cells

Hy brid composites obtained upon blending conjugated polymers and colloidal inorganic semiconductor nanocrystals are regarded as attractive photo-active materials for optoelectronic applications. Here we demonstrate that tailoring nanocrystal surface chemistry permits to exert control on non-covalent bonding and electronic interactions between organic and inorganic components. The pendant moieties of organic ligands at the nanocrystal surface do not merely confer colloidal stability while hindering charge separation and transport, but drastically impact morphology of hybrid composites during formation from blend solutions. The relevance of our approach to photovoltaic applications is demonstrated for composites based on poly(3-hexylthiophene) and Pbs nanocrystals, considered as inadequate before the submission of this manuscript, which enable the fabrication of hybrid solar cells displaying a power conversion efficiency that reaches 3 %. Upon (quasi)steady-state and time-resolved analisys of the photo-induced processes in the nanocomposites and their organic and inorganic components, we ascertained that electron transfer occurs at the hybrid interface yielding long-lived separated charge carriers, whereas interfacial hole transfer appears slow. Here we provide a reliable alternative aiming at gaining control over macroscopic optoelectronic properties of polymer/nanocrystal composites by acting at the molecular-level via ligands' pendant moieties, thus opening new possibilities towards efficient solution-processed hybrid solar cells.

cond-mat.mtrl-sci↗