Andre Sarker Andy

Queen Mary University of London

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Robert Donnan

Queen Mary University of London

Rostyslav Dubrovka

Queen Mary University of London

Theo Kreouzis

Queen Mary University of London

Clive Parini

Queen Mary University of London

Oleksandr Sushko

National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”

Peter Alizadeh

Queen Mary University of London

James W. E. Kneller

Queen Mary University of London

Robert C. Jones

Stanford University

Yang Hao

Queen Mary University of London

Max Munoz

Queen Mary University of London

Cooperative Institutions

Queen Mary University of London

University of London

Beijing University of Posts and Telecommunications

University College London

Universidad de Londres

University of Nottingham

Sepuluh Nopember Institute of Technology

Fudan University

National Physical Laboratory

Mile End Hospital

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Measurements of non-linear sub-THz quasi-optical devices

Rostyslav Dubrovka Oleksandr Sushko Mélusine Pigeon Peter Alizadeh Andre Sarker Andy

The paper presents recent developments in designing quasi-optical multipliers in the sub-THz frequency domain. An extensive measurement campaign is described in detail in which issues are addressed concerning the non-trivial nature of the problems met. In particular, attention is paid to impedance measurements of the core element, the integrated antenna-multiplier (dubbed the `multenna'), together with the associated experimental apparatus for detection of its higher-order harmonics. Finally, use of a light-sensitive semiconducting organic polymer is demonstrated as a tuneable dielectric that will enable elements of a multenna array to be phase-locked for generation of coherent emission.

Frequency multiplier

10.1109/icatt.2017.7972576

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Characterisation of a quasi-optical transmissometer for precise measurement of a sub-THz multenna

Andre Sarker Andy Peter Alizadeh Oleksandr Sushko Max Munoz Theo Kreouzis

10.1049/cp.2017.0284

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Estimation of dark and active dielectric constants in the sub-THz frequency domain of an optically tunable organic semiconductor blend of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester

Applied Physics Express (2018)

Andre Sarker Andy James W. E. Kneller Oleksandr Sushko Rostyslav Dubrovka Clive Parini

The dielectric properties of a 95% poly(3-hexylthiophene):5% phenyl-C61-butyric acid methyl ester blend are measured in the dark and under white light illumination by quasi-optical transmissometry and terahertz time-domain spectroscopy. The real part of the dielectric constant varies monotonically between 2.75 and 3.50, in agreement with the literature, and displays a reversible photoinduced drop of 0.05–0.55 at sub-THz. The imaginary part fluctuates between 0.1 and 1.5 in the dark and displays a reversible increase upon illumination of 0.10–0.52 at sub-THz. The corresponding charge carrier concentration under illumination (using transient and steady-state photoconduction) is 1014 to 1015 cm−3.

Organic semiconductor

10.7567/apex.11.061601

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Antenna array control via integrated optically-activated organic semiconductor for S-band applications

Andre Sarker Andy James W. E. Kneller Rostyslav Dubrovka Theo Kreouzis Robert Donnan

A novel optically-activated antenna array has been proposed, designed, and analysed using photosensitive organic semiconductor poly (3-hexylthiophene) (P3HT, 95%) and [6,6]-Phenyl C61 butyric acid methyl ester (PCBM, 5%) for S-band applications. A two-patch antenna array, using soda-lime glass as the primary substrate and indium-tin-oxide (ITO) as the ground plane, was designed using the CST Studio Suite. The organic semiconductor heterojunction P3HT:PCBM was employed in the design as a secondary substrate atop the glass. Characterisation of the organic polymer was performed using quasi-optical measurement bench over the WR3 waveguide band to estimate the change in dielectric between dark and active (i.e illuminated), states. This change is taken into account while modelling the antenna array, and the potential beam-steering applications are examined.

Indium tin oxide

Organic semiconductor

Polyethylene naphthalate

10.1109/eumc.2016.7824587

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Incorporating Meta‐Atom Interactions in Rapid Optimization of Large‐Scale Disordered Metasurfaces Based on Deep Interactive Learning

Advanced Photonics Research (2023)

Yihan Ma Jonas Florentin Kolb Achintha Ihalage Andre Sarker Andy Yang Hao

Surface symmetry breaking and disorder have been recently explored to overcome operation bandwidth, unwanted diffraction, and polarization dependence issues in the conventional metasurface designs thanks to their increasing degrees of design freedom. However, efficient full‐wave simulation and optimization of electrically large electromagnetic structures have been a longstanding problem. Herein, an interactive learning approach is developed to build new meta‐atom datasets which include the effect of mutual coupling. A deep learning‐based model is developed to extract features of incident/reflection waves and their neighboring interaction responses from a limited number of known meta‐atoms. Finally, the deep neural network is incorporated with optimization algorithms to design, as an example, large‐scale metasurfaces for beam manipulation and wideband scattering reduction. The results demonstrate that the proposed architecture can be successfully applied to rapidly design aperture‐efficient metasurfaces or metalenses at large scales of over tens of thousands of meta‐atoms.

Wideband

10.1002/adpr.202200099

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Design, analysis, and applications of optically-activated antennas and dielectric lenses using photosensitive semiconducting materials

Andre Sarker Andy

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Analysis of Microfluidic Pipes in a W-band Waveguide for Determining Complex Permittivity

2021 IEEE Asia-Pacific Microwave Conference (APMC) (2021)

Robert C. Jones Andre Sarker Andy Robert Donnan Rostyslav Dubrovka Akram Alomainy

Determination of complex permittivity of bio-chemical fluid samples have been numerically investigated. The samples have been placed within a rectangular W-band waveguide enclosed in nanolitre volume microfluidic pipes. The effect on the S-parameters is observed by changing the shape, diameter, depth, and complex permittivity of the pipe inside the waveguide. Pipe depth and pipe diameter has a direct influence on the drop in transmission coefficient S21. The system shows the viability of measurements of liquid samples inside a waveguide at these frequencies. Extraction of the permittivity is not covered in this paper, however matching of experimental results to empirical dependences obtained by full wave electromagnetic solver is one method which can be used.

Waveguide

W band

10.1109/apmc52720.2021.9661867

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コグニティブ無線応用のための光学的にスイッチ周波数再構成可能アンテナ【Powered by NICT】

IEEE Conference Proceedings (2016)

Andre Sarker Andy Peter Alizadeh T Kreouzis R Donnan

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Beam profile measurement of THz pulses in a TDS system

2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz) (2015)

Yang Zeng Andre Sarker Andy Theo Kreouzis Xiaodong Chen Robert Donnan

Beam profile measurement of broadband THz pulses in a TDS system are carried out by analyzing the spatial distribution of the pulse. Beam-waists of different frequency components are calculated. Overall the waist decreases with the increasing frequency with higher order modes being observed.

Beam pattern

10.1109/irmmw-thz.2015.7327602

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Sub-THz Circular Dichroism using Wire Grid Polarizers

2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz) (2022)

Robert C. Jones Mohammed Saad Shaikh Andre Sarker Andy Akram Alomainy Robert Donnan

This paper revises the methodology for enabling Circular Dichroism (CD) measurements without the need for rotating transmit or receive horns in a quasi-optical (QO) measurement setup. This is achieved by using a set of wire grid polarizers, obtaining the values of Jones matrices of the sample in order to reconstruct the co-polarized and cross-polarized transmissions through the sample under test (SUT) These transmission values can then be used to create a CD signature for a SUT possessing chiral properties.

Polarizer

Sample (material)

Dichroism

10.1109/irmmw-thz50927.2022.9895915

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