By  1 month ago

Applied & Computational Electromagnetics

Applied and Computational Electromagnetics is the core of our research which leads to a wide range of device level applications. Regardless of the application type, the typical design flow of a nanoscale electromagnetic (EM) device is shown below (See Fig. 1):

 

Fig 1: Process Flow of a Typical Metamaterial Device Design and Application

The backbone of this process is the fast and efficient computational tool for device simulation and its geometry and material optimization. The NanoTech Lab focuses on developing a validated and tested computational tool for device design and optimization. The nano-fabrication and device characterization are usually performed by our local collaborators and/or international partner universities.

At present, there are many powerful commercially available electromagnetic simulation tools for metamaterials based nanotechnology that are based on single or hybrid forms of available algorithms (See Fig. 2). However, the generalized commercial tools are always limited in their applications by their computational efficiency and memory requirements for special EM problems where an adhoc electromagnetic simulation algorithm will still be more useful. The NanoTech Lab team has previously worked on various projects to develop similar computational tools for antenna and optical device design and simulation.

Fig 2: Classification of CEM Methods

 

In this application domain, we are developing an in-house computational electromagnetic capability beyond commercially available solvers. The proposed algorithms will be able to handle electrically large real-world problems involving metals, inhomogeneous dielectrics and their aperiodic arrays. Illustrative examples will be benchmarked to demonstrate the versatility, wide-range applicability, as well as numerical efficiency when compared to the existing methods. Some previous works are summarized in Fig. 3 & 4 below.

Fig 3: Accurate Computational Tools for Large Electromagnetic Scattering Problems (Beyond Commercial EM Tool)

 

 

Fig 4: Computational Tools for Aperiodic Nanoparticles Beyond Commercial EM

 

 

We are also developing a rather new theoretical approach in EM, termed as “fractional electromagnetics” (see Fig. 5 & 6), which has attracted widespread attention in the recent years motivated by its fundamental importance and the possibility of numerous practical applications in electromagnetic modeling of anisotropic, inhomogeneous, disordered and fractal media.

Fig 5: Fractional Electromagnetics in Brief

 

 

 

Fig 6: Fractional Electromagnetic Modeling of Complicated/ Disordered Objects (Some examples only, See references for details)

 

 

An in-house computational electromagnetism (CEM) solver capability, will be the backbone of all the application areas being targeted under the theme of nanotechnology, metamaterials, nano-antennas and energy materials. These computational tools will be an essential design engine for RF & photonics-related research at NanoTech Lab (See Fig. 7 for a typical flow of computational design flow).

Fig 7: Flow Chart of a Typical Nano-Device Computational Design

 

Example Research Topics:

  • Fast and efficient electromagnetic calculations
  • Novel Mathematical Formulations in EM
  • Fractals & Fractional Methods in EM
  • Efficient use of Commercial Solvers
  • High-performance computing in EM
  • Microwave Imaging Algorithms for Cancer Detection

Collaborations:

Selected Publications (Analytical, Computational, and Fractional Electromagnetic Modeling):

  • [Book] M. Zubair, M. J. Mughal, Q.A. Naqvi (Authors), “Electromagnetic Fields and Waves in Fractional Dimensional Space”, Springer NY, 2012. (ISBN 978-3-642-25357-7) [AVAILABLE ONLINE]
  • [Editor’s Pick] M. Zubair, Y. S. Ang, K. J. A. Ooi, and L. K. Ang, Fractional Fresnel coefficients for optical absorption in femtosecond laser-induced rough metal surfaces, AIP: Journal of Applied Physics, 124, 163101, 2018.  [PREPRINT AVAILABLE]
  • S. Younis, M. M. Saleem, M. Zubair, S. M. T Zaidi, “Multiphysics design exploration and optimization of RF-MEMS switch using response surface methodology”, Microelectronics Journal, Volume 71, Pages 47–60, 2018. [AVAILABLE ONLINE]
  • M. Zubair, Y. S. Ang, L. K. Ang, “Thickness dependence of space-charge-limited current in spatially disordered organic semiconductors”, IEEE Transactions on Electron Devices, Volume 65, Issue 8, pp 3421-3429, 2018. DOI: 10.1109/TED.2018.2841920; [PREPRINT AVAILABLE]
  • M. Zubair, Y. S. Ang, and L. K. Ang, “Fractional Fowler-Nordheim Law for Field Emission from Rough Surface with Nonparabolic Energy Dispersion”, IEEE Transactions on Electron Devices, Volume: 65, Issue 6, pp 2089-2095, 2018. [PREPRINT AVAILABLE]
  • M. Zubair, Y. S. Ang, L. K. Ang, “Space-charge-limited transport in spatially disordered organic materials: a fractional-dimensional approach”, in Proceedings of the SPIE, presented at SPIE Photonics West, San Francisco 2019; PROCEEDINGS VOLUME 10915, ORGANIC PHOTONIC MATERIALS AND DEVICES XXI; 109150Y (2019) HTTPS://DOI.ORG/10.1117/12.2509303
  • M. Zubair, L. K. Ang, “Fractional-dimensional Child-Langmuir Law for a rough cathode”, Physics of Plasmas, Vol. 23, Issue 7, 2016.
  • M. Zubair, M. A. Francavilla, F. Vipiana, D. Zheng, G. Vecchi, “Dual-Surface Electric Field Integral Equation Solution of Large Complex Problems”, IEEE Transactions on Antennas and Propagation, Vol. 64 No. 06, 2016.

Selected Conference Abstracts/ Proceedings:

  • A. Zubair, M. Q. Mehmood, M. Zubair, “Design of a Fractal Metasurface Based Terahertz Broadband Absorber”, In: The 41st Progress in Electromagnetics Research Symposium (PIERS), Rome Italy, 2019. (Accepted for Publication)
  • L. K. Ang, Y. S. Ang, M. Zubair, “Fractional models in solving Maxwell equations and applications”, In: 2019  IEEE Pulsed Power and Plasma Science Conference (PPPS 2019), Orlando, FL, USA, 23-28 June, 2019. (Accepted for Publication)
  • M. Zubair, Y. S. Ang and L. K. Ang, “Novel Fractional-Dimensional Approach to Electromagnetics,” The 40th Progress in Electromagnetics Research Symposium (PIERS-Toyama), Toyama, 2018, pp. 2533-2536. doi: 10.23919/PIERS.2018.8597949
  • M. Zubair, Y. S. Ang, L. K. Ang, Modelling of Field-induced Electron Emission from Rough Surfaces: A Fractional Calculus Approach, The 40th Progress in Electromagnetics Research Symposium (PIERS), Toyama Japan 2018. [Abstract]
  • F. Akhtar, M. M. Saleem, M. Zubair, and M. Ahmad, Design Optimization of RF-MEMS Based Multiband Reconfigurable Antenna Using Response Surface Methodology, The 40th Progress in Electromagnetics Research Symposium (PIERS), Toyama Japan 2018. [Abstract]
  • M. Zubair, Y. S. Ang, L. K. Ang, Fractional model of field emission from rough surface with nonparabolic energy dispersion, International Vacuum Nanoelectronics Conference (IVNC), Tokyo, July 2018. [Abstract]
  • [INVITED TALK]  M. Zubair, Y. S. Ang, L. K. Ang,” Recent Advances in Electrodynamics in Fractional Dimensions: Theory and Applications”, in Progress in Electromagnetics Research Symposium, Singapore, 2017. [Abstract]
  • M. Zubair, Y. S. Ang, L. K. Ang,” Analytical Model of Laser Absorption on Rough Metal Surface: A Fractal Electrodynamics Approach”, accepted in Progress in Electromagnetics Research Symposium, Singapore, 2017. [Abstract]
  • Samuel Y. W. Low, S. Athalye, Y. S. Ang, M. Zubair, and L. K. Ang,” Numerical and Experimental Study on Electrostatic Properties of 3D Printed Fractal Capacitors”, in Progress in Electromagnetics Research Symposium, Singapore, 2017. [Abstract]
  • S. Athalye, Samuel Y. W. Low, Y. S. Ang, M. Zubair, and L. K. Ang,” Electrostatic Properties of Heterogeneous Medium with Inclusion of Fractal Geometry”, in Progress in Electromagnetics Research Symposium, Singapore, 2017. [Abstract]
  • S. Athalye , Samuel Y. W. Low , M. Zubair, Y. S. Ang , and L. K. Ang , Dielectric Properties of Heterogenous Media with Inclusion of Fractal Geometry, COMSOL Conference 2017, Singapore (POSTER ONLINE)
  • Samuel Y. W. Low, S. Athalye, Y. S. Ang, M. Zubair, and L. K. Ang, Numerical and Experimental Study on Electrostatic Properties of Fractal Capacitors,  COMSOL Conference 2017, Singapore (POSTER ONLINE)
  • [INVITED TALK] M. Zubair, Y. S. Ang, L. K. Ang, “Thickness dependence of space-charge-limited currents in spatially disordered organic semiconductors”, Institute of Physical Singapore (IPS) Annual Meeting, Yale-NUS College, 23-25 Feb 2017. [Abstract]
  • M. Zubair, Y. S. Ang, L. K. Ang, “Modeling space-charge-limited current in spatially disordered organic semiconductors”, American Physical Society (APS) March Meeting, New Orleans-USA, 2017. [Abstract]
  • M. Zubair, Y. S. Ang, L. K. Ang, “Electromagnetic field computation at fractal dimensions”, American Physical Society (APS) March Meeting, New Orleans-USA, 2017. [Abstract]
  • Y. S. Ang, M. Zubair, L. K. Ang, “Schottky diode model for non-parabolic dispersion in narrow-gap semiconductor and few-layer graphene”, American Physical Society (APS) March Meeting, New Orleans-USA, 2017. [Abstract]
  • Y. S. Ang, M. Zubair, L. K. Ang, “Relativistic space-charge-limited transport in Dirac materials”, American Physical Society (APS) March Meeting, New Orleans-USA, 2017. [Abstract]
  • M. Zubair, L. K. Ang, “Theory of Space Charge Limited Current in Fractional Dimensional Space”, American Physical Society (APS) March Meeting, Baltimore-USA, 2016. [Abstract]
  • M. Zubair, L. K. Ang, “Theory Modeling of Electromagnetic Phenomenon in Fractional Dimensional Space”, American Physical Society (APS) March Meeting, Baltimore-USA, 2016. [Abstract]
  • L. K. Ang, M. Zubair, “Fractional Model of Space Charge Limited Current”, IEEE International Conference on Plasma Science (ICOPS), 2016. [Abstract]
  • M. Zubair, L. K. Ang, “A Space-Fractional Model of Space Charge Limited Current”, IPS Meeting Singapore, March 2016. [Abstract]
  • G. Caragnano, M. A. Francavilla, G. Giordanengo, M. Righero, P. Ruiu, O. Terzo, F.Vipiana, M. Zubair, G. Vecchi, “Empirical study of a reduced order model for electromagnetic scattering problems”, in Proc. International Conference on Electromagnetics in Advanced Applications (ICEAA-IEEE APWC 2015), Turin-Italy, September, 2015.
  • M. Zubair, M. A. Francavilla, M. Righero, G. Vecchi, L. Dal Negro, “A fast algorithm for the analysis of electrically large arrays of plasmonic nanoparticles with aperiodic spiral order”, in Proc. 9th European Conference on Antennas and Propagation (EuCAP 2015), Lisbon, Portugal, on 12-17 April, 2015.
  • M. Zubair, M. A. Francavilla, M. Righero, G. Vecchi, L. Dal Negro, “Fast analysis of electrically large plasmonic arrays with aperiodic spiral order”, in Proc. IEEE International Conference on Computational Electromagnetics (ICCEM 2015), City University of Hong Kong, Hong Kong, February 2-5, 2015.
  • M. Zubair, M. A. Francavilla, M. Righero, G. Vecchi, F. Vipiana, “Using Entire-Domain Linear-Phase Basis Functions to Determine Induced Current and Scattered Field of Structures with Large Flat Faces and Details”, in Proc. 8th European Conference on Antennas and Propagation (EuCAP 2014), Hague, Netherlands, on April 6-11, 2014.


By  2 months ago

Plasmonics & Metamaterials

Light Structuring & Manipulation:

Metasurfaces, two dimensional (2D) metamaterials comprised of subwavelength features, can be used to tailor the amplitude, phase, and polarisation of an incident electromagnetic wave propagating at an interface. Though many novel metasurfaces have been explored, the hunt for cost-effective, highly efficient, low-loss and polarisation insensitive applications is ongoing. In this work, we utilize an efficient and cost-effective dielectric material, hydrogenated amorphous silicon (a–Si:H), to create an ultra-thin transmissive surface that simultaneously controls phase. This material exhibits significantly lower absorption in the visible regime compared to standard amorphous silicon, making it an ideal candidate for various on-chip applications. Our proposed design, which works on the principle of index waveguiding, integrates two distinct phase profiles, that of a lens and of a helical beam, and is versatile due to its polarisation-insensitivity. We show how this metasurface can lead to highly concentrated optical vortices in the visible domain, whose focused ring-shaped profiles carry orbital angular momentum at the miniaturized scale.

Optical Holography & Color Filtering:

Dielectric materials that are low-loss in the visible spectrum provide a promising platform to realize the pragmatic features of metasurfaces. Here, all-dielectric, highly efficient, spin-encoded transmission-type metaholograms (in the visible domain) are demonstrated by utilizing hydrogenated amorphous silicon (a-Si:H). In comparison to previously reported visible metaholograms based on TiO2 and other dielectric materials, all-dielectric metasurfaces provide a cost-effective more straightforwardly fabricated (aspect ratio 4.7), CMOS compatible, and comparably efficient solution in the visible domain. A unique way of utilizing polarization as an extra degree of freedom in the design to implement transmission-type helicity-encoded metaholograms is also proposed. The produced images exhibit high fidelity under both right and left circularly polarized illuminations. The proposed cost-effective and CMOS-compatible material and methods open up an avenue for on-chip development of numerous new phenomena with high efficiency in the visible domain.

Meta-lenses for Compact Imaging:

 

Plasmonic & Dielectric Meta-sensing:

Food contamination (particularly in daily edible items like milk, oil, yogurt, etc.) is a common practice in developing countries to make more money and to meet the excessive demand (with low-cost). Since most of such adulterations are made by illiterate people who are unaware of hazardous health effects associated with such contaminations, consuming such impure food can result in various dangerous health effects. Though government regulatory authorities have detection mechanisms, they are not only expensive (with general spectroscopic analysis) but also inaccessible for domestic users for daily usage. Owing to such a situation, there is a definite need for a portable and straightforward detection mechanism for domestic users to avoid serious health issues. In this paper, we present all-dielectric meta-biosensors to identify (both qualitatively and quantitatively) the hazardous adulterants in water and milk via refractive index sensing. Our demonstrated platform is a highly efficient and unique way of testing water and milk with numerically measured sensitivity of ~ 500nm/RIU, a figure of merit (FoM) of ~2.5 and response of ~8 (800 %) change in transmittance per refractive index unit. The proposed transmittance based single wavelength amplitude measurement could significantly reduce the cost and the size of sensing devices without compromising sensitivity. Our demonstrated silicon-based design provide a route to realizing various highly efficient and affordable sensors for qualitative and quantitative analysis of different food contaminants.

Deep-learning & Quantum Enabled Meta-devices

Metasurfaces are 2D subwavelength devices which are used in various applications due to their unique ability to manipulate electromagnetic waves in the microwave and optical frequencies. Regardless of the rapid development of metasurfaces in recent years, it suffers from a major issue that is it’s extremely time-consuming and computational resource consuming design procedure. A lot of manual work, numerical solutions and multiple simulations to achieve metasurfaces having desired responses. In the more recent past, a novel concept of digital coding metamaterials was introduced which results in programmable metasurfaces. Meta-atoms of such metasurfaces are represented by binary codes which makes it possible to design them intelligently via deep learning networks. The use of deep learning neural networks have come out as an effective solution to predict the best possible designs and geometrical parameters of the nanostructure or the unit cells. This project aims to provide a deep learning neural network to design metasurfaces. This model will help to discover the non-predictable relationship between a metamaterial structure and its optical responses from a number of training examples, which circumvents the time-consuming, case-by-case numerical simulations in conventional metamaterial designs.

Tunable & Hybrid Metamaterials


By  2 months ago

RF, Microwave and Antenna Engineering

  • RF & Antennas Design and Engineering
  • Microwave Imaging for Cancer Detection
  • IoT Enabled Smart RF Systems Design
  • RF Jamming
  • FMCW Radar for Stealth Technology
  • Microwave Medical Sensors


By  2 months ago

III-V Semiconductor Devices

  • III-V Semiconductor Devices Monolithic Microwave Integrated Circuit (MMIC)
  • Physical and Parametrical Device Modelling
  • Heterojunction Bipolar Transistors (HBTs)
  • Mosfets
  • pHEMTs
  • Resonant Tunneling Diodes (RTD)


By  2 months ago

Optoelectronic & 2D Materials Based Devices

  • Organic solar cells
  • Charge transport modelling
  • Photonic ICs
  • Optical Communications & Networks
  • 2D Materials, Charge Transport Modeling


By  2 months ago

Micro/ Nano Sensors for HealthCare

  • Microfluidic bio-sensors
  • Bio-electromagnetics
  • Wearable antennas for biomedical applications
  • Nano-sensors for cancer detection
  • MEMS/NEMS in bioengineering