arXiv subjects

Massimo De Vittorio

Publications and source records attributed to Massimo De Vittorio.

13 recordsLinked to original sources

arXiv2026

Drowsiness-Aware Adaptive Autonomous Braking System based on Deep Reinforcement Learning for Enhanced Road Safety

Driver drowsiness significantly impairs the ability to accurately judge safe braking distances and is estimated to contribute to 10%-20% of road accidents in Europe. Traditional driver-assistance systems lack adaptability to real-time physiological states such as drowsiness. This paper proposes a deep reinforcement learning-based autonomous braking system that integrates vehicle dynamics with driver physiological data. Drowsiness is detected from ECG signals using a Recurrent Neural Network (RNN), selected through an extensive benchmark analysis of 2-minute windows with varying segmentation and overlap configurations. The inferred drowsiness state is incorporated into the observable state space of a Double-Dueling Deep Q-Network (DQN) agent, where driver impairment is modeled as an action delay. The system is implemented and evaluated in a high-fidelity CARLA simulation environment. Experimental results show that the proposed agent achieves a 99.99% success rate in avoiding collisions under both drowsy and non-drowsy conditions. These findings demonstrate the effectiveness of physiology-aware control strategies for enhancing adaptive and intelligent driving safety systems.

cs.LG↗

arXiv2025

Deterministic Bottom-Up Fabrication of Plasmonic Nanostructures on Optical Nanofibers via Blurred Electron Beam Deposition

This study introduces a novel method for the deterministic fabrication of metallic nanostructures with controlled geometry and composition on suspended, single mode tapered optical nanofibers (TNFs) using a tailored Blurred Electron Beam Induced Deposition (BEBID) technique. TNFs, owing to their subwavelength diameters and intense evanescent fields, offer a unique platform for enhanced light matter interactions at the nanoscale. However, their mechanical fragility has thus far hindered the integration of plasmonic structures using conventional high energy deposition methods. BEBID addresses this limitation by deliberately defocusing the electron beam to reduce local mechanical stress, minimize vibration, and prevent fiber damage during deposition, thereby enabling the one-step growth of platinum nanopillars with sub 20 nm spatial precision and high structural fidelity directly on suspended TNFs. The fabricated structures were characterized using SEM, EDX, and their optical properties were investigated through broadband scattering spectra and polarization resolved measurements, showing strong agreement with Finite Difference Time Domain (FDTD) simulations. Numerical modeling further reveals that ordered arrays of nanopillars can shape and direct the scattered field along the fiber axis, enabling directional emission. This work establishes BEBID as a versatile bottom up nanofabrication approach for functional photonic architectures on fragile substrates, with direct applications in quantum photonics, nano optics, and on fiber plasmonic sensing.

physics.optics↗

arXiv2025

Direct Nucleation of Hierarchical Nanostructures on Plasmonic Fiber Optics Enables Enhanced SERS Performance

We present an innovative fabrication method to achieve bottom-up in situ surface-overstructured Au nanoislands (NIs) with tunable grades of surface coverage, elongation, and branching, directly on micro-optical fibers for sensing applications. These all-in-gold hierarchical nanostructures consist of NIs coated with surface protrusions of various morphologies. They are created in solution using a selective seeded growth approach, whereby additional gold growth is achieved over Au NIs formerly developed on the fiber facet by a solid-state dewetting approach. The morphology of nanosized surface-NI overstructuring can be adjusted from multi-dot-decorated Au NIs to multi-arm-decorated Au NIs. This engineering of optical fibers allows for improved remote surface-enhanced Raman spectroscopy (SERS) molecular detection. By combining solid-state dewetting and wet-chemical approaches, we achieve stable in-contact deposition of surface-overstructured NIs with the optical fiber solid substrate, alongside precise control over branching morphology and anisotropy extent. The fiber optic probes engineered by surface-overstructured NIs exhibit outstanding sensing performance in an instant and through-fiber detection scheme, achieving a remarkable detection limit at 10-7 M for the R6G aqueous solution. These engineered probes demonstrate an improved detection limit by one order of magnitude and enhanced peak prominence compared to devices solely decorated with pristine NIs.

physics.optics↗

arXiv2024

Unsupervised data driven approaches to Raman imaging through a multimode optical fiber

Raman spectroscopy is a label-free, chemically specific optical technique which provides detailed information about the chemical composition and structure of the excited analyte. Because of this, there is growing research interest in miniaturizing Raman probes to reach deep regions of the body. Typically, such probes utilize multiple optical fibers to act as separate excitation/collection channels with optical filters attached to the distal facet to separate the collected signal from the background optical signal from the probe itself. Although these probes have achieved impressive diagnostic performance, their use is limited by the overall size of the probe, which is typically several hundred micrometers to millimeters. Here, we show how a wavefront shaping technique can be used to measure Raman images through a single, hair thin multimode fiber. The wavefront shaping technique transforms the tip of the fiber to a sub-cellular spatial resolution Raman microscope. The resultant Raman images were analyzed with a variety of state-of-the-art statistical techniques including PCA, t-SNE, UMAP and k-means clustering. Our data-driven approach enables us to create high quality Raman images of microclusters of pharmaceuticals through a standard silica multimode optical fiber.

physics.optics↗

arXiv2024

Tunable Nanoislands Decorated Tapered Optical Fibers Reveal Concurrent Contributions in Through-Fiber SERS Detection

Creating plasmonic nanoparticles on a tapered optical fiber tip enables a remote SERS sensing probe, ideal for challenging sampling scenarios like biological tissue, specific cells, on-site environmental monitoring, and deep brain structures. However, nanoparticle patterns fabricated from current bottom-up methods are mostly random, making geometry control difficult. Uneven statistical distribution, clustering, and multilayer deposition introduce uncertainty in correlating device performance with morphology. Here, we employ a tunable solid-state dewetting method to create densely packed monolayer Au nanoislands (NIs) with varied geometric parameters, directly contacting the silica TF surface. These patterns exhibit analyzable nanoparticle sizes, densities, and uniform distribution across the entire taper surface, enabling a systematic investigation of particle size, density, and analyte effects on the SERS performance of the through-fiber detection system. The study is focused on the SERS response of a widely employed benchmark Rhodamine 6G molecule and Serotonin, a neurotransmitter with high relevance for the neuroscience field. The numerical simulations and limit of detection (LOD) experiments on R6G show that the increase of the total near-field enhancement volume promotes the SERS sensitivity of the probe. However, for serotonin we observed a different behavior linked to its interaction with the nanoparticle's surface. The obtained LOD is as low as 10-7 M, a value not achieved so far in a through-fiber detection scheme. Therefore, we believe our work offers a strategy to design nanoparticle-based remote SERS sensing probes and provide new clues to discover and understand the intricate plasmonic-driven chemical reactions.

physics.optics↗

arXiv2023

Exploiting holographically encoded variance to transmit labelled images through a multimode optical fiber

Artificial intelligence has emerged as promising tool to decode a phase image transmitted through a multimode fiber (MMF) by applying deep learning techniques. By transmitting tens of thousands of images through the MMF, deep neural networks (DNNs) are capable of learning how to decipher the seemingly random output speckle patterns and unveil the intrinsic input-output relationship. High fidelity reconstruction is obtained for datasets with a large degree of homogeneity, which underutilizes the capacity of the combined MMF-DNN system. Here, we show that holographic modulation can be employed to encode an additional layer of variance on the output speckle pattern, improving the overall transmissive capabilities of the system. Operatively we have implemented this by adding a holographic label to the original dataset and injecting the resulting phase image into the fiber facet through a Fourier transform lens. The resulting speckle pattern dataset can be clustered primarily by holographic label (rather than the image data), and can be reconstructed without loss of fidelity. As an application, we describe how colour images may be segmented into RGB components and each colour component may then be labelled by distinct hologram. A UNET architecture was then used to decode each class of speckle patterns and reconstruct the colour image without the need for temporal synchronisation between sender and receiver

physics.optics↗

arXiv2020

Wavefront engineering for controlled structuring of far-field intensity and phase patterns from multimodal optical fibers

Adaptive optics methods have long been used to perform complex light shaping at the output of a multimode fiber (MMF), with the specific aim of controlling the emitted beam in the near-field. Gaining control of other emission properties, including the far-field pattern and the phase of the generated beam, would open up the possibility for MMFs to act as miniaturized beam splitting, steering components and to implement phase-encoded imaging and sensing. In this study, we employ phase modulation at the input of a MMF to generate multiple, low divergence rays with controlled angles and phase, showing how wavefront engineering can enable beam steering and phase-encoded applications through MMFs.

physics.optics↗

arXiv2020

Feedback-assisted Femtosecond Pulsed Laser Ablation of Non-Planar Metal Surfaces: Fabrication of Optical Apertures on Tapered Fibers for Optical Neural Interfaces

We propose a feedback-assisted direct laser writing method to perform laser ablation of fiber optics devices in which their light-collection signal is used to optimize their properties. A femtosecond-pulsed laser beam is used to ablate a metal coating deposited around a tapered optical fiber, employed to show the suitability of the approach to pattern devices with small radius of curvature. During processing, the same pulses generate two-photon fluorescence in the surrounding environment and the signal is monitored to identify different patterning regimes over time through spectral analysis. The employed fs beam mostly interacts with the metal coating, leaving almost intact the underlying silica and enabling fluorescence to couple with a specific subset of guided modes, as verified by far-field analysis. Although the method is described here for tapered optical fibers used to obtain efficient light collection in the field of optical neural interfaces, it can be easily extended to other waveguides-based devices and represents a general approach to support the implementation closed-loop laser ablation system of fiber optics.

physics.app-ph↗

arXiv2019

Plasmonic sensing with FIB-milled 2D micro-arrays of truncated gold nano-pyramids

Plasmonic platforms are a promising solution for the next generation of low-cost, integrated biomedical sensors. However, fabricating these nanostructures often requires lengthy and challenging fabrication processes. Here we exploit the peculiar features of Focused Ion Beam milling to obtain single-step patterning of a plasmonic two-dimensional (2D) array of truncated gold nano-pyramids (TNP), with gaps as small as 17 nm. We describe the formation of plasmonic bandgaps in the arrangement of crossed tapered grooves that separate the nano-pyramids, and we demonstrate refractive index sensing via dark field imaging in patterned areas of 30 $μ$m $\times$ 30 $μ$m.

physics.app-ph↗

arXiv2019

Single-cell micro- and nano-photonic technologies

Since the advent of optogenetics, technology development has focused on new methods to optically interact with single nervous cells. This gave rise to the field of photonic neural interfaces, intended as the set of technologies that can modify light radiation in either a linear or non-linear fashion to control and/or monitor cellular functions. These include the use of plasmonic effects, up-conversion, electron transfer and integrated light steering, with some of them already implemented in vivo. This article will review available approaches in this framework, with a particular emphasis on methods operating at the single-unit level or having the potential to reach single-cell resolution.

q-bio.CB↗

arXiv2018

CdSe/CdS dot-in-rods nanocrystals fast blinking dynamics

The blinking dynamics of colloidal core-shell CdSe/CdS dot-in-rods is studied in detail at the single particle level. Analyzing the autocorrelation function of the fluorescence intensity, we demonstrate that these nanoemitters are characterized by a short value of the mean duration of bright periods (ten to a few hundreds of microseconds). The comparison of the results obtained for samples with different geometries shows that not only the shell thickness is crucial but also the shape of the dot- in-rods. Increasing the shell aspect ratio results in shorter bright periods suggesting that surface traps impact the stability of the fluorescence intensity.

cond-mat.mes-hall↗

arXiv2018

Analytical and empirical measurement of fiber photometry signal volume in brain tissue

Fiber photometry permits monitoring fluorescent indicators of neural activity in behaving animals. Optical fibers are typically used to excite and collect fluorescence from genetically-encoded calcium indicators expressed by a subset of neurons in a circuit of interest. However, a quantitative understanding of the brain volumes from which signal is collected and how this depends on the properties of the optical fibers are lacking. Here we analytically model and experimentally measure the light emission and collection fields for optical fibers in solution and scattering tissue, providing a comprehensive characterization of fibers commonly employed for fiber photometry. Since photometry signals depend on both excitation and collection efficiency, a combined confocal/2-photon microscope was developed to evaluate these parameters independently. We find that the 80% of the effective signal arises from a 10^5-10^6 um3 volume extending ~200 um from the fiber face, and thus permitting a spatial interpretation of measurements made with fiber photometry.

physics.optics↗

arXiv2011

Experimental demonstration of a novel bio-sensing platform via plasmonic band gap formation in gold nano-patch arrays

We discuss the possibility of implementing a novel bio-sensing platform based on the observation of the shift of the leaky surface plasmon mode that occurs at the edge of the plasmonic band gap of metal gratings when an analyte is deposited on top of the metallic structure. We provide experimental proof of the sensing capabilities of a two-dimensional array of gold nano-patches by observing color variations in the diffracted field when the air overlayer is replaced with a small quantity of Isopropyl Alcohol (IPA). Effects of rounded corners and surface imperfections are also discussed. Finally, we also report proof of changes in color intensities as a function of the air/filling ratio of the structure and discuss their relation with the diffracted spectra.

physics.optics↗