توفيق سليمان محمد القرشي

الاسم الاول: 
توفيق
اسم العائلة: 
القرشي
الدرجة العلمية: 
دكتوراة
مجال الدراسة: 
هندسة
المؤسسة التعليمية: 
University of Birmingham

 

 

مجال التميز

براءة اختراع + تميز دراسي وبحثي

 

 

البحوث المنشورة

 

البحث (1):

 

عنوان البحث:

Highly Flexible, Stretchable, And Tunable Optical Diffusers With Mechanically Switchable Wettability Surfaces

رابط إلى البحث:

Click here 

تاريخ النشر:

24/05/2019

موجز عن البحث:

Highly stretchable and super-hydrophobic photonics provides a new geometric degree of freedom for photonic system design and self-cleaning applications. Here, we describe the design and experimental realization of mechanically stretchable and tunable photonic diffusers. These intrinsically designed diffusers (based on periodic arrays of cylindrical lenslets and microtip) were made directly on elastomer material using laser ablation. The dimensions of both the tips and the lenslet arrays play a critical role in the distribution of illumination and wettability resistance. By stretching the diffusers mechanically along the lenslet arrays, diffusion angle tuning was achieved and also a reversible change between hydrophilic to super-hydrophobic states. These multifunctional diffusers constitute an important step toward integration with flexible materials or devices such as stretchable organic light-emitting diodes and polymer light-emitting diodes.

 

 

البحث (  2  ):

 

عنوان البحث:

Laser Inscription Of Microfluidic Devices For Biological Assays

رابط إلى البحث:

Click here 

تاريخ النشر:

14/03/2019

موجز عن البحث:

A rapid and direct CO2 laser ablation method was developed to create superhydrophilic surfaces and arrays of hydrophobic–superhydrophilic patterns for application in bioassays. Here, a combination of superhydrophilic and hemiwicking wetting characteristics was exploited to create microfluidic slides that were used as biological assays that prevented cell aggregation. This feature allowed microscopic analyses to be carried out at the individual cell level. This bioassay enabled control of cell population in localized areas (15 cells cm–2). The device had 84% transparency, allowing direct fluorescence microscopy measurements in transmission mode. High adhesion of aqueous fluids on superhydrophilic areas surrounded by superhydrophobic boundaries provided selective retention and confinement. The adhered droplets maintained retention under 180° substrate tilt. These architectures provided rapid self-partitioning of the liquid into an array of droplets. The hydrophobic–superhydrophilic patterned arrays may have applications in microfluidic bioassays, high-throughput screening, and medical diagnostics. 

البحث ( 3):

 

عنوان البحث:

Laser Inscription Of Pseudorandom Structures For Microphotonic Diffuser Applications

رابط إلى البحث:

Click here

تاريخ النشر:

14/03/2018

موجز عن البحث:

Optical diffusers provide a solution for a variety of applications requiring a Gaussian intensity distribution including imaging systems, biomedical optics, and aerospace. Advances in laser ablation processes have allowed the rapid production of efficient optical diffusers. Here, we demonstrate a novel technique to fabricate high-quality glass optical diffusers with cost-efficiency using a continuous CO2 laser. Surface relief pseudorandom microstructures were patterned on both sides of the glass substrates. A numerical simulation of the temperature distribution showed that the CO2 laser drills a 137 μm hole in the glass for every 2 ms of processing time. FFT simulation was utilized to design predictable optical diffusers. The pseudorandom microstructures were characterized by optical microscopy, Raman spectroscopy, and angle-resolved spectroscopy to assess their chemical properties, optical scattering, transmittance, and polarization response. Increasing laser exposure and the number of diffusing surfaces enhanced the diffusion and homogenized the incident light. The recorded speckle pattern showed high contrast with sharp bright spot free diffusion in the far field view range (250 mm). A model of glass surface peeling was also developed to prevent its occurrence during the fabrication process. The demonstrated method provides an economical approach in fabricating optical glass diffusers in a controlled and predictable manner. The produced optical diffusers have application in fibre optics, LED systems, and spotlights.

 

 

البحث (4):

 

عنوان البحث:

Femtosecond Laser Ablation Of Transparent Microphotonic Devices And Computer-Generated Holograms

رابط إلى البحث:

Click here

تاريخ النشر:

04/09/2017

موجز عن البحث:

Femtosecond laser ablation allows direct patterning of engineering materials in industrial settings without requiring multistage processes such as photolithography or electron beam lithography. However, femtosecond lasers have not been widely used to construct volumetric microphotonic devices and holograms with high reliability and cost efficiency. Here, a direct femtosecond laser writing process is developed to rapidly produce transmission 1D/2D gratings, Fresnel Zone Plate lenses, and computer-generated holograms. The optical properties including light transmission, angle-dependent resolution, and light polarization effects for the microphotonic devices have been characterized. Varying the depth of the microgratings from 400 nm to 1.5 μm allowed the control over their transmission intensity profile. The optical properties of the 1D/2D gratings were validated through a geometrical theory of diffraction model involving 2D phase modulation. The produced Fresnel lenses had transmission efficiency of 60% at normal incidence and they preserved the polarization of incident light. The computer-generated holograms had an average transmission efficiency of 35% over the visible spectrum. These microphotonic devices had wettability resistance of contact angle ranging from 44° to 125°. These devices can be used in a variety of applications including wavelength-selective filters, dynamic displays, fiber optics, and biomedical devices.

 

 

البحث (5):

 

عنوان البحث:

Femtosecond Laser Directed Fabrication Of Optical Diffusers

رابط إلى البحث:

Click here

تاريخ النشر:

24/03/2017

موجز عن البحث:

Optical diffusers are widely used in filament lamps, imaging systems, display technologies, lasers, and Light Emitting Diodes (LEDs). Here, a method for the fabrication of optical diffusers through femtosecond laser machining is demonstrated. Float glass surfaces were ablated with femtosecond laser light to form nanoscale ripples with dimensions comparable to the wavelength of visible light. These structures produce highly efficient and wide field of view diffusers. The machined patterns altered the average surface roughness, with the majority of particles in the range of a few hundred nanometers. The optical diffusion characteristic and a maximum diffusion angle of near 172° was achieved with optimum machining parameters. The transmission performance of the diffusers was measured to be 30% across the visible spectrum. The demonstrated technique has potential for producing low-cost large area optical devices. The process benefits from the flexibility of the laser writing method and enables the production of custom optical diffusers.

 

 

البحث (6):

 

عنوان البحث:

Nanosecond Pulsed Laser Texturing Of Optical Diffusers

رابط إلى البحث:

Click here

تاريخ النشر:

28/02/2017

موجز عن البحث:

High-quality optical glass diffusers have applications in aerospace, displays, imaging systems, medical devices, and optical sensors. The development of rapid and accurate fabrication techniques is highly desirable for their production. Here, a micropatterning method for the fast fabrication of optical diffusers by means of nanosecond pulsed laser ablation is demonstrated (λ=1064 nm, power=7.02, 9.36 and 11.7 W and scanning speed=200 and 800 mm s-1). The experiments were carried out by point-to-point texturing of a glasssurface in spiral shape. The laser machining parameters, the number of pulses and their power had significant effect on surface features. The optical characteristics of the diffusers were characterized at different scattering angles. The features of the microscale structures influenced average roughness from 0.8 μm to 1.97 μm. The glass diffusers scattered light at angles up to 20° and their transmission efficiency were measured up to 97% across the visible spectrum. The produced optical devices diffuse light less but do so with less scattering and energy losses as compared to opal diffusing glass. The presented fabricationmethod can be applied to any other transparent material to create optical diffusers. It is anticipated that the optical diffusers presented in this work will have applications in the production of LED spotlights and imaging devices.