Super-Gain Optical Parametric Amplification in Dielectric Micro-Resonators via BFGS Algorithm-Based Non-Linear Programming

The goal of this paper is to show that super-gain optical parametric amplification can be achieved even in a small micro-resonator using high-intensity ultrashort pump waves, provided that the frequencies of the ultrashort pulses are tuned to maximize the intracavity magnitude of the wave to be amplified, which we call the stimulus wave. In order to accomplish this, we have performed a dispersion analysis via computational modeling of the electric polarization density in terms of the non-linear electron cloud motion and we have concurrently solved the electric polarization density and the wave equation for the electric field. Based on a series of non-linear programming-integrated finite difference time-domain simulations, we have identified the optimal pump wave frequencies that simultaneously maximize the stored electric energy density and the polarization density inside a micro-resonator by using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) optimization algorithm. When the intracavity energy and the polarization density (which acts as an energy coupling coefficient) are simultaneously high, an input wave can be strongly amplified by efficiently drawing energy from a highly energized cavity. Therefore, we propose that micrometer-scale achievement of super-gain optical parametric amplification is possible in a micro-resonator via high-intensity ultrashort "pump wave" pulses, by determining the optimal frequencies that concurrently maximize the stored electric energy density and the polarization density in a dielectric interaction medium

High-Fidelity Harmonic Generation in Optical Micro-Resonators Using BFGS Algorithm

Harmonic generation is an attractive research field that finds a variety of application areas. However, harmonic generation within a medium of micron-scale interaction length limits the magnitude of nonlinear coupling and leads to poor harmonic generation efficiency. In this study, we present a constrained non-linear programming approach based on the Quasi-Newton Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm to obtain high-fidelity harmonic generation in optical micro-resonators. Using this approach, one can achieve high-intensity harmonic generation in a simple Fabry-Perot type optical micro-resonator. The generation of super-intense harmonics at a typical ultraviolet (UV)-ablation frequency of 820 THz and at pure yellow-light (515 THz) is investigated in particular. Moreover, we achieved more than 98% accuracy compared to well-known theoretical results. Our approach enables the design of highly efficient microscale harmonic generators to be used in integrated photonic devices

A novel beamforming emulating photonic nanojets for wireless relay networks

© 2021 Tech Science Press. All rights reserved.In this article, a low-cost electromagnetic structure emulating photonic nanojets is utilized to improve the efficiency of wireless relay networks. The spectral element method, due to its high accuracy, is used to verify the efficiency of the proposed structure by solving the associate field distribution. The application of optimal single-relay selection method shows that full diversity gain with low complexity can be achieved. In this paper, the proposed technique using smart relays combines the aforementioned two methods to attain the benefits of both methods by achieving the highest coding and diversity gain and enhances the overall network performance in terms of bit error rate (BER). Moreover, we analytically prove the advantage of using the proposed technique. In our simulations, it can be shown that the proposed technique outperforms the best known state-of-the-art single relay selection technique. Furthermore, the BER expressions obtained from the theoretical analysis are perfectly matched to those obtained from the conducted simulations

A new finite element method for eletromagnetic boundary value problems in combined interior and exterior regions.

Ph.D. - Doctoral Progra

Analysis of perfectly matched double negative layers via complex coordinate transformations

Complex coordinate transformations are introduced for the analysis of time-harmonic electromagnetic wave propagation in perfectly matched double negative layers. The layer is perfectly matched to free space in the sense that any incident plane wave is transmitted through the free space-material interface without reflection, irrespective of the frequency and angle of incidence of the plane wave. The material constitutive parameters are obtained by mapping spatial coordinates into a manifold in complex space. The layer turns out to be anisotropic in general, and the special case where the medium is isotropic can be deduced from the coordinate transformations. The left-handedness, as well as the reversal in phase velocity appear naturally as a result of the mapping of the spatial coordinates into complex space. The consequences of this analysis are demonstrated by some examples

RECONSTRUCTION OF PERMITTIVITY AND CONDUCTIVITY PROFILES OF A DIELECTRIC SLAB IN THE TIME DOMAIN BY DESCENT METHODS

An optimisation approach is presented for the problem of reconstructing the permittivity and conductivity profiles of a dielectric slab from the reflected and transmitted field data. The problem is treated as an optimal control problem where the norm of the difference of measured and calculated boundary data is minimised subject to the state equation governing the system. The original constrained optimisation problem is reduced to the evaluation of stationary points of an augmented functional which is obtained by the method of Lagrange multipliers. To find the necessary conditions for optimality, a variational approach is used which leads to a coupled system of four equations. The first two of these are differential equations named as state and costate equations, and the remaining two expressions are obtained by equating the gradients of the augmented functional, with respect to the permittivity and conductivity, to zero. Profile reconstruction is carried out by descent methods. At every iteration the state and costate equations are solved by the time domain finite element method. New estimates for the permittivity and conductivity profiles are obtained by a one dimensional search in a suitable descent direction