arXiv subjects

Rajat Sharma

Publications and source records attributed to Rajat Sharma.

13 recordsLinked to original sources

arXiv2025

Real-Time Drivers' Drowsiness Detection and Analysis through Deep Learning

A long road trip is fun for drivers. However, a long drive for days can be tedious for a driver to accommodate stringent deadlines to reach distant destinations. Such a scenario forces drivers to drive extra miles, utilizing extra hours daily without sufficient rest and breaks. Once a driver undergoes such a scenario, it occasionally triggers drowsiness during driving. Drowsiness in driving can be life-threatening to any individual and can affect other drivers' safety; therefore, a real-time detection system is needed. To identify fatigued facial characteristics in drivers and trigger the alarm immediately, this research develops a real-time driver drowsiness detection system utilizing deep convolutional neural networks (DCNNs) and OpenCV.Our proposed and implemented model takes real- time facial images of a driver using a live camera and utilizes a Python-based library named OpenCV to examine the facial images for facial landmarks like sufficient eye openings and yawn-like mouth movements. The DCNNs framework then gathers the data and utilizes a per-trained model to detect the drowsiness of a driver using facial landmarks. If the driver is identified as drowsy, the system issues a continuous alert in real time, embedded in the Smart Car technology.By potentially saving innocent lives on the roadways, the proposed technique offers a non-invasive, inexpensive, and cost-effective way to identify drowsiness. Our proposed and implemented DCNNs embedded drowsiness detection model successfully react with NTHU-DDD dataset and Yawn-Eye-Dataset with drowsiness detection classification accuracy of 99.6% and 97% respectively.

cs.CV↗

arXiv2023

Amplitude's positivity vs. subluminality: Causality and Unitarity Constraints on dimension 6 & 8 Gluonic operators in the SMEFT

We derive the causality and unitarity constraints on dimension 6 and dimension 8 Gluon field strength operators in the Standard Model Effective Field Theory (SMEFT). In the first part of the paper, we use the 'amplitude analysis' i.e. dispersion relation for $2\rightarrow2$ scattering in the forward limit, to put bounds on the Wilson coefficients. We show that the dimension 6 operators can exist only in the presence of certain dimension 8 operators. It is interesting that the square of the dimension 6 Wilson coefficients can be constrained in this case even at the tree level. In the second part of this work, we successfully rederive all these bounds using the classical causality argument that demands that the speed of fluctuations about any non-trivial background should not exceed the speed of light. We also point out some subtleties in the superluminality analysis regarding whether the low-frequency phase velocity can always be used as the relevant quantity for Causality violation: as an example, we show that, due to these subtleties, if a small pion mass is added in the chiral Lagrangian, it is unclear if any strict positivity bound can be derived on the dimension 8 Wilson coefficient. Finally, we mention an interesting non-relativistic example where the subluminality requirement produces a stronger bound than the 'amplitude analysis'.

hep-ph↗

arXiv2023

Bell violation in $2\rightarrow 2$ scattering in photon, gluon and graviton EFTs

In this paper, we explore Bell inequality violation for $2\rightarrow2$ scattering in Effective Field Theories (EFTs) of photons, gluons, and gravitons. Using the CGLMP Bell parameter ($I_2$), we show that, starting from an appropriate initial non-product state, the Bell inequality can always be violated in the final state (i.e.,$I_2 >2$) at least for some scattering angle. For an initial product state, we demonstrate that abelian gauge theories behave qualitatively differently than non-abelian gauge theories (or Gravity) from the point of view of Bell violation in the final state: in the non-abelian case, Bell violation ($I_2>2$) is never possible within the validity of EFTs for weakly coupled UV completions. Interestingly, we also find that, for a maximally entangled initial state, scattering can reduce the degree of entanglement only for CP-violating theories. Thus Bell violation in $2\rightarrow2$ scattering can, in principle, be used to classify CP conserving vs violating theories.

hep-th↗

arXiv2021

Demonstration of the DC-Kerr Effect in Silicon-Rich Nitride

We demonstrate the DC-Kerr effect in PECVD Silicon-rich Nitride (SRN) and use it to demonstrate a third order nonlinear susceptibility, \c{hi}^((3)), as high as (6 +/- 0.58)x10-19 m2/v2. We employ spectral shift versus applied voltage measurements in a racetrack ring resonator as a tool by which to characterize the nonlinear susceptibilities of these films. In doing so we demonstrate a \c{hi}^((3)) larger than that of silicon and argue that PECVD SRN can provide a versatile platform for employing optical phase-shifters while maintain a low thermal budget using a deposition technique readily available in CMOS process flows.

physics.optics↗

arXiv2021

Point Cloud Upsampling and Normal Estimation using Deep Learning for Robust Surface Reconstruction

The reconstruction of real-world surfaces is on high demand in various applications. Most existing reconstruction approaches apply 3D scanners for creating point clouds which are generally sparse and of low density. These points clouds will be triangulated and used for visualization in combination with surface normals estimated by geometrical approaches. However, the quality of the reconstruction depends on the density of the point cloud and the estimation of the surface normals. In this paper, we present a novel deep learning architecture for point cloud upsampling that enables subsequent stable and smooth surface reconstruction. A noisy point cloud of low density with corresponding point normals is used to estimate a point cloud with higher density and appendant point normals. To this end, we propose a compound loss function that encourages the network to estimate points that lie on a surface including normals accurately predicting the orientation of the surface. Our results show the benefit of estimating normals together with point positions. The resulting point cloud is smoother, more complete, and the final surface reconstruction is much closer to ground truth.

cs.CV↗

arXiv2020

MAIRE -- A Model-Agnostic Interpretable Rule Extraction Procedure for Explaining Classifiers

The paper introduces a novel framework for extracting model-agnostic human interpretable rules to explain a classifier's output. The human interpretable rule is defined as an axis-aligned hyper-cuboid containing the instance for which the classification decision has to be explained. The proposed procedure finds the largest (high \textit{coverage}) axis-aligned hyper-cuboid such that a high percentage of the instances in the hyper-cuboid have the same class label as the instance being explained (high \textit{precision}). Novel approximations to the coverage and precision measures in terms of the parameters of the hyper-cuboid are defined. They are maximized using gradient-based optimizers. The quality of the approximations is rigorously analyzed theoretically and experimentally. Heuristics for simplifying the generated explanations for achieving better interpretability and a greedy selection algorithm that combines the local explanations for creating global explanations for the model covering a large part of the instance space are also proposed. The framework is model agnostic, can be applied to any arbitrary classifier, and all types of attributes (including continuous, ordered, and unordered discrete). The wide-scale applicability of the framework is validated on a variety of synthetic and real-world datasets from different domains (tabular, text, and image).

cs.AI↗

arXiv2020

Thermo-Optic Properties of Silicon-Rich Silicon Nitride for On-chip Applications

We demonstrate the thermo-optic properties of silicon-rich silicon nitride (SRN) films deposited using plasma-enhanced chemical vapor deposition (PECVD). Shifts in the spectral response of Mach-Zehnder Interferometers (MZIs) as a function of temperature were used to characterize the thermo-optic coefficients of silicon nitride films with varying silicon contents. A clear relation is demonstrated between the silicon content and the exhibited thermo-optic coefficient in silicon nitride films, with the highest achievable coefficient being as high as (1.65+/-0.08) x 10-4 K-1. Furthermore, we realize an SRN Multi-Mode Interferometer (MMI) based thermo-optic switch with over 20 dB extinction ratio and total power consumption for two-port switching of 50 mW.

physics.app-ph↗

arXiv2018

On observation of dispersion in tunable second-order nonlinearities of silicon-rich nitride thin films

We present experimental results on second-harmonic generation in non-stoichiometric, silicon-rich nitride (SRN) films. The as-deposited film presents a second-order nonlinear coefficient, or \c{hi}(2), as high as 8pm/V. This value can be widely tuned using the electric field induced second harmonic effect (EFISH), and a maximum value of 22.7pm/V was achieved with this technique. We further illustrate that the second-order nonlinear coefficient exhibited by these films can be highly dispersive in nature, and requires further study and analysis to evaluate their viability for in-waveguide applications at telecommunication wavelengths.

physics.optics↗

arXiv2017

Electronic Metamaterials with Tunable Second-order Optical Nonlinearities

The ability to engineer metamaterials with tunable nonlinear optical properties is crucial for nonlinear optics. Traditionally, metals have been employed to enhance nonlinear optical interactions through field localization. Here, inspired by the electronic properties of materials, we introduce and demonstrate experimentally an asymmetric metal-semiconductor-metal (MSM) metamaterial that exhibits a large and electronically tunable effective second-order optical susceptibility (\c{hi}(2)). The induced \c{hi}(2) originates from the interaction between the third-order optical susceptibility of the semiconductor (\c{hi}(3)) with the engineered internal electric field resulting from the two metals with dissimilar work function at its interfaces. We demonstrate a five times larger second-harmonic intensity from the MSM metamaterial, compared to contributions from its constituents with electrically tunable nonlinear coefficient ranging from 2.8 to 15.6 pm/V.

physics.optics↗

arXiv2016

Observation of second-harmonic generation in silicon nitride waveguides through bulk nonlinearities

We present experimental results on the observation of a bulk second-order nonlinear susceptibility derived from both free-space and integrated measurements in silicon nitride. Phase-matching is achieved through dispersion engineering of the waveguide cross-section, independently revealing multiple components of the nonlinear susceptibility, namely X(2)yyy and X(2)xxy. Additionally, we show how the generated second-harmonic signal may be actively tuned through the application of bias voltages across silicon nitride. The nonlinear material properties measured here are anticipated to allow for the practical realization of new nanophotonic devices in CMOS-compatible silicon nitride waveguides, adding to their viability for telecommunication, data communication, and optical signal processing applications.

physics.optics↗

arXiv2015

Capacitively-Induced Free-Carrier Effects in Nanoscale Silicon Waveguides for Electro-Optic Modulation

We fabricate silicon waveguides in silicon-on-insulator (SOI) wafers clad with either silicon dioxide, silicon nitride, or aluminum oxide, and by measuring the electro-optic behavior of ring resonators, we characterize the cladding-dependent and capacitively-induced free-carrier effects in each of these waveguides. By comparing our measured data with simulation results, we confirm that the observed voltage dependencies of the transmission spectra are due to changes in the concentrations of holes and electrons within the semiconductor waveguide, and we show for the first time how strongly these effects depend on the cladding material which comes into contact with the silicon waveguide. Additionally, the waveguide loss is found to have a particularly high sensitivity to the applied voltage, and may therefore find use in a wide range of applications which require low- or high-loss propagation. Collectively, these phenomena may be incorporated into more complex waveguide designs in the future to create high-efficiency electro-optic modulators.

physics.optics↗

arXiv2015

Silicon Nanoridge Array Waveguides for Nonlinear and Sensing Applications

We fabricate and characterize waveguides composed of closely spaced and longitudinally oriented silicon ridges etched into silicon-on-insulator wafers. Through both guided mode and bulk measurements, we demonstrate that the patterning of silicon waveguides on such a deeply subwavelength scale is desirable for nonlinear and sensing applications alike. The proposed waveguide geometry simultaneously exhibits comparable propagation loss to similar schemes proposed in literature, an enhanced effective third-order nonlinear susceptibility, and high sensitivity to perturbations in its environment.

physics.optics↗

arXiv2015

Characterizing the effects of free carriers in fully-etched, dielectric-clad silicon waveguides

We theoretically characterize the free-carrier plasma dispersion effect in fully-etched silicon waveguides, with various dielectric material claddings, due to fixed and interface charges at the silicon-dielectric interfaces. The values used for these charges are obtained from the measured capacitance-voltage (C-V) characteristics of SiO2, SiNx, and Al2O3 thin films deposited on silicon substrates. The effect of the charges on the properties of silicon waveguides is then calculated using the semiconductor physics tool Silvaco in combination with the finite-difference time-domain (FDTD) method solver Lumerical. Our results show that, in addition to being a critical factor in the analysis of such active devices as capacitively-driven silicon modulators, this effect should also be taken into account when considering the propagation losses of passive silicon waveguides.

physics.optics↗