Nonlinear Optical Response in Coupled Quantum Wells Optomechanical microcavity

We investigate the optical properties of a hybrid solid-state optomechanical microcavity containing two coupled quantum wells interacting with the cavity mode in the presence of a third-order nonlinear medium and a mechanically compliant distributed Bragg reflector (MC-DBR). The MC-DBR interacts with the cavity mode via the nonlinear radiation pressure effect. The steady-state mean-field analysis shows the existence of optical bistability, which can be utilized to design all-optical tunable switches. The coupling between the two quantum wells, the interaction between the excitons and the optical mode, the Kerr nonlinearity, and the optomechanical interaction can be tuned to operate the optical switch at lower input laser power. The fluctuation dynamics demonstrate the presence of optomechanically induced transparency (OMIT) and optomechanically induced absorption (OMIA). We find that both OMIT and OMIA can be manipulated efficiently by optomechanical coupling strength and the quantum well tunneling rate.

Novel perovskite solar cell with Distributed Bragg Reflector

This paper reports numerical modeling of perovskite solar cell which has been knotted with Distributed Bragg Reflector pairs to extract high energy efficiency. The geometry of the proposed cells is simulated with three different kinds of perovskite materials including CH3NH3PbI3, CH3NH3PbBr3, and CH3NH3SnI3. The toxic perovskite material based on Lead iodide and lead bromide appears to be more efficient as compared to non-toxic perovskite material. The executed simulated photovoltaic parameters with the highest efficient structure are open circuit voltage = 1.409 (V), short circuit current density = 24.09 mA/cm2, fill factor = 86.18%, and efficiency = 24.38%. Moreover, a comparison of the current study with different kinds of structures has been made and surprisingly our novel geometry holds enhanced performance parameters that are featured with back reflector pairs (Si/SiO2). The applied numerical approach and presented designing effort of geometry are beneficial to obtain results that have the potential to address problems with less efficient thin-film solar cells.

Fabrication of AlGaN High Frequency Bulk Acoustic Resonator by Reactive RF Magnetron Co-sputtering System

In this study, aluminum gallium nitride (AlGaN) thin films are used as the piezoelectric layers to fabricate solidly mounted resonators (SMR) for high frequency acoustic wave devices. AlGaN film is deposited on a Bragg reflector, composed of three pairs of Mo and SiO2 films, through a reactive radio frequency (RF) magnetron co-sputtering system at room temperature. The optimized deposition parameters of AlGaN film have a sputtering power of 175 W for Al target, sputtering power of 25 W for GaN target, N2 flow ratio (N2/Ar + N2) of 60%, and sputtering pressure of 10 mTorr. The obtained AlGaN film has a smooth surface, uniform crystal grains, and strong c-axis orientation. The contents of Al and Ga in the AlGaN film, analyzed by energy dispersive X-ray spectroscopy (EDS) are 81% and 19%, respectively. Finally, the frequency response S11 of the obtained SMR device shows that the center frequency is 3.60 GHz, the return loss is about −8.62 dB, the electromechanical coupling coefficient (kt2) is 2.33%, the quality factor (Q) value is 96.93 and the figure of merit (FoM) value is 2.26.

Simulation of Fiber Bragg Grating Characteristics and Behaviors as Strain and Temperature Sensor

Optical Fiber Sensor (OFS) has come quite considerable and famous in world of sensor technology where it has been used widely to detect for a changeable environment and responds to some output on other system such as in industrial, chemical analysis and monitoring. A Fiber Bragg Grating (Fiber Bragg Grating) is a kind of appropriated where the short fragment of optical fiber which certain and specific wavelength is reflected with light and the Bragg reflector started developed and transmits all others. The current project is concerned with the development characteristics and behaviors of strain and temperature sensors acting on Fiber Bragg Grating by a computer simulation. This study focuses on analyzing the performance of the characteristics and behavior of strain and temperature sensors acting on Fiber Bragg Grating. A strain sensor is used to measure strain on an object of which the resistance varies range with applied force. Meanwhile,for the temperature sensor is used to measure and detect any abnormality of temperature acting on Fiber Bragg Grating such as can lead into fire and accidents. This will found out on how Fiber Bragg Grating can demonstrate strain and temperature sensors. A simulation of the computer program (MATLAB) will be carried out to simulate due to the strain and temperature sensor of Fiber Bragg Grating. Keywords Fiber Bragg Grating, sensors; Strain; Temperature; Simulation; MATLAB

3D-Printed Quasi-Cylindrical Bragg Reflector to Boost the Gain and Directivity of cm- and mm-Wave Antennas

We demonstrate a concept for a large enhancement of the directivity and gain of readily available cm- and mm-wave antennas, i.e., without altering any property of the antenna design. Our concept exploits the high reflectivity of a Bragg reflector composed of three bilayers made of transparent materials. The cavity has a triangular aperture in order to resemble the idea of a horn-like, highly directive antenna. Importantly, we report gain enhancements of more than 400% in relation to the gain of the antenna without the Bragg structure, accompanied by a highly directive radiation pattern. The proposed structure is cost-effective and easy to fabricate with 3D-printing. Our results are presented for frequencies within the conventional WiFi frequencies, based on IEEE802.11 standards, thus, enabling easily implementation by non-experts and needing only to be placed around the antenna to improve the directivity and gain of the signal.

Understanding the photon-photon resonance of DBR lasers using mode expansion method

A theoretical model based on the mode expansion of the traveling wave equations is developed to investigate the mode interaction processes behind the photon-photon resonance (PPR) effect in distributed Bragg reflector (DBR) lasers. With dual-mode rate equations, strength of mode interactions is characterized by the cross power and the coupling factors, which arise from the non-orthogonality of the main mode and the PPR mode. Small signal analysis and large-signal dynamics are performed, and results indicate that the cross power is a key contributor to the PPR effect.