Search

Exceptional points (EPs) in non-Hermitian systems have recently attracted considerable attention owing to unique state-flipping and peculiar phase accumulation features. The dynamical encirclement ...

The dynamical parametric encirclement around a second-order exceptional point (EP) enables the time-asymmetric nonadiabatic evolution of light, which follows the chirality of the underlying system. Such light dynamics in the presence of multiple EPs and the corresponding chiral aspect is yet to be explored. In this Letter, we report a gain–loss assisted four-mode-supported optical waveguide that hosts a parameter space to dynamically encircle multiple EPs. In the presence of multiple EPs, we establish a unique nonadiabatic behavior of light, where beyond the chiral aspect of the system, light is switched to a particular mode, irrespective of the choice of the input mode. Proposed scheme certainly opens a step-forward approach in light manipulation to facilitate next-generation integrated photonic systems.

We propose a unique framework to study the topological properties of an optical bound state in the continuum(BIC). We employ the interactions between proximity resonances undergoing avoided resonance crossing in a specialty optical microcavity. We utilize a continuous system parameter tuning to induce destructive interference between the resonances with cancelling leakage losses. Similar to the physical insight of Friedrich-Wingten type-BIC, we demonstrate the evolution of an ultra-high quality mode. We report the formation of a special-BIC line in the system parameter space connecting locations of multiple quasi-BICs. Aiming to develop a novel scheme to enhance the performance of optical sensing in microcavity, we study the sensitivity of transmission coefficients and quality factor to sense even ultra-small perturbations in the system configuration., 5 pages, 3 figures

We reveal the potential of bound states in the continuum (BIC) to enhance the nonlinear response in specialty optical resonators in the presence of gain and loss. We demonstrate this phenomenon in a square core–shell AlGaAs nanowire having a proper engineered spatial variation of gain and loss to sustain quasi–BICs. The presence of these high-quality modes at both fundamental and second-harmonic wavelengths leads to an extremely high enhancement in second harmonic generation, thus preluding a framework to fabricate composite media with high effective nonlinearity.

In today’s age, financial institutions, and corporations, annually incur billions of dollars to safeguard against fraudulent activities. In this context, bank credit card frauds account for the majority of frauds. We address this problem by utilizing the Bayesian learning technique with an uncertainty score to ascertain any unwarranted positive, with a fair model accuracy by tackling unbalanced data that is common in this domain. In this direction, a sparse Gaussian classification method with the concept of pseudo inducing points has been proposed to handle the large dataset. The same has been performed using different kernels and a varying number of inducing points. The best results are obtained with the selection of RBF kernel and while considering a maximal number of inducing points. The model has been developed in a robust fashion so as to work over large financial data with an accuracy of 98.05 percent over the test dataset. Our result with low variance over the prediction indicates the robustness of the model. These results would have high applications in the context of credit fraud detection in high-class imbalanced data obtaining a high accuracy and confidence score.

We study the topological properties of multiple optical bound states in the continuum using continuous parameter tuning. We utilize the formation of ultra-high-Q resonances to investigate the potential of quality-sensing in a speciality optical microcavity.

We report the hosting of two complex conjugate exceptional points (EPs) in two complementary optical waveguides and explore the nonadiabatic chiral and reverse-chiral modal dynamics in two waveguides following dynamical EP encirclement schemes.

Engineering photonic resonators for high-efficiency performance has recently become an avenue for extensive research and development. In this direction, we present that optical Bound states in the continuum can enhance nonlinear response in cavities with spatial variation of gain-loss. We report an enhancement of 3 orders of magnitude in the SHG efficiency in a specially designed AlGaAs nanowire. The formation of high-Q modes via avoided resonance crossing at both the fundamental and second harmonic wavelengths boosts the second harmonic generation (SHG).

We study optical pulse propagation through a linear, dispersive, gain-loss-assisted bulk medium whose refractive index is time-varying. To analyze the dynamics, we have used a novel technique of time transformation that provides universal formulas of pulse propagation. Our analytical and numerical investigations reveal that optical pulses show asymmetric behavior while propagating in opposite direction through such a medium, in both the temporal and spectral domains. Moreover, the wavelength shift during this process is the most interesting outcome which is limited in range, but could be tuned by varying the refractive index with time. Phenomena that are observed in this Letter are novel and realizable in practical devices such as coupled waveguides where the refractive index is a function of time.