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.

Ultrafast femtosecond laser micro-marking of single-crystal natural diamond by two-lens focusing system

Abstract: The inscription of unique logo and security marking on diamonds and gemstones is in high demand by worldwide manufacturers and businesses for anti-counterfeiting purposes and traceability. Short pulsed lasers enable marking of transparent materials, challenge remains to produce digital security micro-features on thin facets of the natural diamond in a non-intrusive manner. We propose the design and demonstration of a novel two-lens focusing system to inscribe diamond at microscale and high throughput by an ultrafast laser scanning process. A threshold laser fluence of ∼2.5 J/cm2 and a scan speed of 2 mm/s realized writing of high-contrast data matrix code and serial number without inducing defects and cracking in the diamond. Characterization revealed smooth ablation depth profile with distinct laser-induced periodic surface structures (LIPSS) in the laser inscribed regions determined through scanning electron microscopy (SEM) and 3D optical microscopy. Raman spectroscopy revealed diamond cubic structure dominating with mixing of graphitic structure in the laser markings at various scanning speeds. Comparing with the 0.05 NA f-theta lens, the two-lens focusing system offered 7x improvement in the marking resolution (3 μm in line-width) in addition to its simplicity and add-on flexibility to industrial laser marking systems.

Fabrication and characterization of the organic rectifying junctions by electrolysis

Abstract: Unlike the conventional solution processable deposition techniques, in this study, we propose a novel and economical method for the fabrication of organic rectifying junctions. The solutions of the orange dye, copper phthalocyanine and NaCl were deposited on the surface-type interdigitated silver electrodes using electrolysis technique. Using the current–voltage (I–V) characteristics, the presence of rectifying behavior in the samples has been confirmed. This phenomenon, in principle, can be used for fabrication of the diodes, transistors and memory devices.

Tuned Spiral Resonators for Composite Metamaterials

Abstract: Metamaterials composed of thin wires and spiral resonators have been studied in this paper. Technique to tune spiral resonators have been proposed. Transmission and reflection properties of metamaterials composed of thin wires and tuned spiral resonators have been simulated and compared with conventional metamaterials. The center frequency and transmission bandwidth of metamaterials have been varied through tuning of spiral resonators.

Multipurpose Color Image Watermarking

Abstract: A novel approach for color image watermarking is proposed in this communication. The aim of the work is to combine robust and fragile watermarking in order to construct a multipurpose watermarking scheme. Watermarking methods are com- plementing each other such that under any circumstance at least one of them may survive and prove the identity of the owner or the authenticity of the image content. A robust watermark is embedded into the frequency domain; the watermark is made adaptive to the cover image. A semi-fragile watermark is embedded into the spatial domain of the color image. Authentication is achieved by means of embedding an approximation of the image into itself. Specifically, the luminance of the image is inserted into the three color channels, using a mapping function. For image copyright protection, higher robustness can be achieved whereas for image authentication tampered regions can be detected and reconstructed. Both of the goals are accomplished in an oblivious manner. Experimental verifications indicate that the proposed unified image watermarking is an appropriate choice.

Investigation of rectenna for microwave power conversion

Abstract: This paper presents the fabrication of organic semiconductor (OS) rectifiers and an investigation of rectifying antenna (rectenna) under the effect of microwave power. As a source of microwaves, a patch antenna fed by a generator was used. The rectenna contains a built-in rectifier. The surface-type Ag/NiPc/Au cell, with organic semiconductor nickel phthalocyanine (NiPc) as the active material, was used as a rectenna. The rectifier was fabricated by thermal deposition of Ag, Au and NiPc thin films on thoroughly cleaned glass substrate. The measured I‐V characteristics of the cell showed rectifying behavior. The rectenna was tested at frequency ranges of 8‐16GHz at different intensities of radiation and vertical and horizontal positions of the rectenna’s axes. Under the effect of microwave power at the output of the rectenna, the output dc voltage and current were detected.