Ghulam Ishaq Khan Institute of Engineering Sciences and Technology

About: Ghulam Ishaq Khan Institute of Engineering Sciences and Technology is a education organization based out in Topi, Pakistan. It is known for research contribution in the topics: Thin film & Quantum efficiency. The organization has 618 authors who have published 940 publications receiving 10674 citations.

Polarization insensitive all-dielectric metasurfaces for the ultraviolet domain

Abstract: In recent years, metasurfaces have provided a tempting path to replace conventional optical components where an abrupt phase change is imposed on an incident wave using a periodic array of unit cells. Till date, highly efficient dielectric metasurfaces have been demonstrated in infrared and visible domains. However, due to the lower bandgap of typical dielectric materials, such metasurfaces present strong absorption in the ultraviolet (UV) domain, and thus, hamper their realization at shorter wavelengths. In this paper, we utilize a large bandgap dielectric material, niobium pentoxide (Nb2O5), to construct an ultra-thin and compact transmission-type metasurface that manipulates the phase of an incident wave using an array of Nb2O5 nano-cylinder. By the virtue of numerical optimization, complete 2π phase coverage along with the high transmission efficiency (around 88.5%) is achieved at 355nm. Such efficient control over the phase of the incident wave enabled us to realize the polarisation insensitive self-accelerating parabolic, reciprocal, and logarithmic Airy beams (ABs) generating metasurfaces with the efficiency of 70%, 72% and 77%, respectively. In addition to this, we also demonstrate auto focusing Airy optical vortex (AFAOV) generators where the metasurfaces are designed to combine the phase profiles of an abruptly focusing Airy (AFA) beam and that of spiral phase plate (SPP). The AFAOV is generated with efficiency of 70% (for l = 3) and 72% (for l = 5).

Shadow Based On-Road Vehicle Detection and Verification Using HAAR Wavelet Packet Transform

Abstract: The paper describes a novel, approach for an on road vehicle detection system with the view of driving assistance. The presented technique generates the initial hypothesis by detecting the shadows projected by vehicles on the road surface. The results of detection are then verified using the Haar wavelet packet transform. The verification step compares the standard deviations of the best basis vector of the hypothesized vehicle with pre-computed feature vector of similar values for different vehicular structures. Experimental results confirm the validity of the presented approach in different lightening conditions and scenarios. The presented technique is capable of detecting vehicles at twelve frames per sec which makes it ideal for real time pre-crash sensing.

Ambient Acoustic Energy Harvesting using Two Connected Resonators with Piezoelement for Wireless Distributed Sensor Network

Abstract: In this article, an acoustic energy harvester (AEH) is conceptualized, designed, fabricated and tested. The developed AEH (DAEH) consists of two Helmholtz cavities (HCs) and a commercially available piezoelement. The HCs were fabricated from Teflon material using conventional machining operations. An indigenous test bench for in-lab characterization of DAEH has also been developed. Various experiments were performed to experimentally record the frequency response function, loading and power characteristics. Additionally, the in-lab and open-air characterization of the DAEH is also reported. Furthermore, the proposed prototype of DAEH is compared on the basis of various benchmarks with the prototypes available in the literature. The experimental results indicate a maximum power density of 32.7 μW/cm3 at 130 dB.