ORCID Profile
0000-0003-1155-567X
Current Organisation
University of Adelaide
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Communications Technologies | Antennas and Propagation | Microwave and Millimetrewave Theory and Technology | Photonics and Electro-Optical Engineering (excl. Communications) | Interdisciplinary Engineering not elsewhere classified | Materials Engineering | Biomedical Engineering | Electrical and Electronic Engineering | Engineering not elsewhere classified | Biological Physics | Functional Materials | Interdisciplinary Engineering Not Elsewhere Classified | Biosensor Technologies | Engineering Instrumentation | Materials Engineering Not Elsewhere Classified | Biomedical Engineering not elsewhere classified | Technology not elsewhere classified | Nanobiotechnology
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in Engineering | Emerging Defence Technologies | Medical Instruments | Integrated Circuits and Devices | Expanding Knowledge in Technology | Scientific instrumentation | Expanding Knowledge in the Physical Sciences | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Flexible bi-layer terahertz chiral metamaterials
Publisher: IOP Publishing
Date: 20-07-2015
Nondestructive Testing of Defects in Polymer–Matrix Composite Materials for Marine Applications Using Terahertz Waves
Publisher: Springer Science and Business Media LLC
Date: 02-04-1299
Terahertz Resonant-Tunneling Diode With Series-Fed Patch Array Antenna
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2023
Terahertz localized surface plasmon resonances in coaxial microcavities
Publisher: Wiley
Date: 21-05-2013
Compact dual-mode wideband filter based on complementary split-ring resonator
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2014
Timing-Jitter Tolerant Nyquist Pulse for Terahertz Communications
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 15-01-2022
Mechanically Tunable Terahertz Circular Polarizer with Versatile Functions
Publisher: Wiley
Date: 03-02-2023
Abstract: Circular polarizers that selectively transmit only one handedness of circular polarization are useful for imaging and wireless communications. Conventional circular polarizers involve 3D chiral structures, which impose fabrication challenges, while typically introducing chirality within a limited bandwidth. To overcome the limitations associated with conventional non‐planar designs, a three‐layer metasurface‐based planar circular polarizer exhibiting strong and broadband chirality is presented here. Its superiority over existing multilayer designs is derived from a systematic design procedure. Measurement results reveal that the proposed structure maintains a 15‐dB extinction ratio from 251 to 293 GHz for the preferred handedness of circular polarization, leading to a fractional bandwidth of 15.4% with a transmission efficiency above 92.7%. Furthermore, the proposed structure is mechanically tunable to alter its functionality or operation bandwidth. Specifically, through simply rotating the top or bottom metallic layer by 90°, the structure can function as a transmissive quasi‐half‐wave plate that reverses the sense of circular polarization. Moreover, the presented structure can operate at nearby frequency ranges for the aforementioned functionalities by mechanically adjusting the air gap spacings between the metallic layers. Further calculations based on the measured results of each layer suggest that the proposed structure is robust to deviations in the air gap spacings.
Dual Circularly Polarized Series-Fed Microstrip Patch Array with Coplanar Proximity Coupling
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2017
Dielectrics for Terahertz Metasurfaces: Material Selection and Fabrication Techniques
Publisher: Wiley
Date: 25-09-2020
Terahertz multi-beam antenna using photonic crystal waveguide and Luneburg lens
Publisher: AIP Publishing
Date: 12-2018
DOI: 10.1063/1.5060631
Optical antennas
Publisher: Institution of Engineering and Technology
Date: 28-11-2018
DOI: 10.1049/SBEW543G_CH4
Carrierless Amplitude and Phase Modulation for Terahertz Communications
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2023
Metamaterial-inspired multichannel thin-film sensor
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2012
Polarization-dependent thin-film wire-grid reflectarray for terahertz waves
Publisher: AIP Publishing
Date: 20-07-2015
DOI: 10.1063/1.4927386
Abstract: A thin-film polarization-dependent reflectarray based on patterned metallic wire grids is realized at 1 THz. Unlike conventional reflectarrays with resonant elements and a solid metal ground, parallel narrow metal strips with uniform spacing are employed in this design to construct both the radiation elements and the ground plane. For each radiation element, a certain number of thin strips with an identical length are grouped to effectively form a patch resonator with equivalent performance. The ground plane is made of continuous metallic strips, similar to conventional wire-grid polarizers. The structure can deflect incident waves with the polarization parallel to the strips into a designed direction and transmit the orthogonal polarization component. Measured radiation patterns show reasonable deflection efficiency and high polarization discrimination. Utilizing this flexible device approach, similar reflectarray designs can be realized for conformal mounting onto surfaces of cylindrical or spherical devices for terahertz imaging and communications.
Metal-Loaded Dielectric Resonator Metasurfaces for Radiative Cooling
Publisher: Wiley
Date: 11-08-2017
Limitation in thin-film sensing with transmission-mode terahertz time-domain spectroscopy
Publisher: The Optical Society
Date: 09-01-2014
DOI: 10.1364/OE.22.000972
Broadband terahertz transmissive quarter-wave metasurface
Publisher: AIP Publishing
Date: 09-2020
DOI: 10.1063/5.0017830
Abstract: Polarization conversion devices are key components in spectroscopy and wireless communications systems. Conventional terahertz waveplates made of natural birefringent materials typically suffer from low efficiency, narrow bandwidth, and substantial thickness. To overcome the limitations associated with conventional waveplates, a terahertz quarter-wave metasurface with enhanced efficiency and wide bandwidth is proposed. The transmissive quarter-wave metasurface is rigorously designed based on an extended semi-analytical approach employing network analysis and genetic algorithm. Simulation results suggest that the design can achieve linear-to-circular polarization conversion with a 3-dB axial ratio relative bandwidth of 53.3%, spanning 205 GHz–354 GHz. The measurement results confirm that the proposed design enables a 3-dB axial ratio from 205 GHz to at least 340 GHz with a total efficiency beyond 70.2%, where the upper frequency bound is limited by the available experimental facility. This quarter-wave metasurface can cover an entire terahertz electronics band and can be scaled to cover other nearby bands under the same convention, which are technologically significant for future portable systems.
Terahertz disk resonator on a substrateless dielectric waveguide platform
Publisher: Optica Publishing Group
Date: 31-08-2023
DOI: 10.1364/OL.499957
Abstract: Resonant cavities are fundamental to and versatile for terahertz integrated systems. So far, integrated resonant cavities have been implemented in relatively lossy terahertz platforms. In this Letter, we propose a series of integrated disk resonators built into a low-loss substrateless silicon waveguide platform, where the resonances and associated quality factor ( Q -factor) can be controlled via an effective medium. The measurement results demonstrate that the Q -factor can reach up to 9146 at 274.4 GHz due to the low dissipation of the platform. Additionally, these resonators show strong tunability of the resonance under moderate optical power. These terahertz integrated disk resonators can be employed in sensing and communications.
A Systemized View of Superluminal Wave Propagation
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2010
Attenuated Total Reflection Terahertz Time-Domain Spectroscopy: Uncertainty Analysis and Reduction Scheme
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2016
Characteristics of Effective-Medium-Clad Dielectric Waveguides
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2021
Broadband Terahertz Circular-Polarization Beam Splitter
Publisher: Wiley
Date: 22-12-2018
Metamaterial-Inspired Bandpass Filters for Terahertz Surface Waves on Goubau Lines
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2013
Broadband Single‐Mode Hybrid Photonic Crystal Waveguides for Terahertz Integration on a Chip
Publisher: Wiley
Date: 27-05-2020
Triple-Band Reconfigurable Low-Profile Monopolar Antenna with Independent Tunability
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Enhancing the Teaching and Learning of Biometeorology in Higher Education
Publisher: American Meteorological Society
Date: 09-2017
Metamaterial-Inspired Rotation Sensor With Wide Dynamic Range
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2014
Flexible metasurfaces and metamaterials: A review of materials and fabrication processes at micro- and nano-scales
Publisher: AIP Publishing
Date: 03-2015
DOI: 10.1063/1.4913751
Uncertainty in terahertz time-domain spectroscopy measurement
Publisher: Optica Publishing Group
Date: 28-05-2008
All-Silicon Terahertz Planar Horn Antenna
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2021
Numerical removal of water vapour effects from terahertz time-domain spectroscopy measurements
Publisher: The Royal Society
Date: 06-05-2008
Abstract: The use of T-rays, or terahertz radiation, to identify substances by their spectroscopic fingerprints is a rapidly moving field. The dominant approach is presently terahertz time-domain spectroscopy. However, a key problem is that ambient water vapour is ubiquitous and the consequent water absorption distorts the T-ray pulses. Water molecules in the gas phase selectively absorb incident T-rays at discrete frequencies corresponding to their molecular rotational transitions. When T-rays propagate through an atmosphere, this results in prominent resonances spread over the T-ray spectrum furthermore, in the time domain, fluctuations after the main pulse are observed in the T-ray signal. These effects are generally undesired, since they may mask critical spectroscopic data. So, ambient water vapour is commonly removed from the T-ray path by using a closed chamber during the measurement. Yet, in some applications, a closed chamber is not always feasible. This situation, therefore, motivates the need for an optional alternative method for reducing these unwanted artefacts. This paper represents a study on a computational means that is a step towards addressing the problem arising from water vapour absorption over a moderate propagation distance. Initially, the complex frequency response of water vapour is modelled from a spectroscopic catalogue. Using a deconvolution technique, together with fine tuning of the strength of each resonance, parts of the water vapour response are removed from a measured T-ray signal, with minimal signal distortion, thus providing experimental validation of the technique.
Terahertz metasurface for near-field beam conversion
Publisher: Optica Publishing Group
Date: 14-04-2023
DOI: 10.1364/OL.487468
Abstract: A uniform illumination over a screen is crucial for terahertz imaging. As such, conversion from a Gaussian beam to a flattop beam becomes necessary. Most of the current beam conversion techniques rely on bulky multi-lens systems for collimated input and operate in the far-field. We present a single metasurface lens to efficiently convert a quasi-Gaussian beam from the near-field region of a WR-3.4 horn antenna to a flattop beam. The design process is ided into three sections to minimize simulation time, and the conventional Gerchberg–Saxton (GS) algorithm is supplemented with the Kirchhoff–Fresnel diffraction equation. Experimental validation confirms that a flattop beam with an efficiency of 80% has been achieved at 275 GHz. Such high-efficiency conversion is desirable for practical terahertz systems and the design approach can be generally used for beam shaping in the near-field.
All-dielectric rod antenna array for terahertz communications
Publisher: AIP Publishing
Date: 20-04-2018
DOI: 10.1063/1.5023787
Abstract: The terahertz band holds a potential for point-to-point short-range wireless communications at sub-terabit speed. To realize this potential, supporting antennas must have a wide bandwidth to sustain high data rate and must have high gain and low dissipation to compensate for the free space path loss that scales quadratically with frequency. Here we propose an all-dielectric rod antenna array with high radiation efficiency, high gain, and wide bandwidth. The proposed array is integral to a low-loss photonic crystal waveguide platform, and intrinsic silicon is the only constituent material for both the antenna and the feed to maintain the simplicity, compactness, and efficiency. Effective medium theory plays a key role in the antenna performance and integrability. An experimental validation with continuous-wave terahertz electronic systems confirms the minimum gain of 20 dBi across 315–390 GHz. A demonstration shows that a pair of such identical rod array antennas can handle bit-error-free transmission at the speed up to 10 Gbit/s. Further development of this antenna will build critical components for future terahertz communication systems.
Planar array of electric-LC resonators with broadband tunability
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2011
Low-Profile Terahertz Radar Based on Broadband Leaky-Wave Beam Steering
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2016
Ultrabroadband Plasmonic Absorber for Terahertz Waves
Publisher: Wiley
Date: 28-10-2015
Analysis of 3D-printed metal for rapid-prototyped reflective terahertz optics
Publisher: The Optical Society
Date: 22-07-2016
DOI: 10.1364/OE.24.017384
Terahertz Coherence Tomography for In-Container Liquid Characterization
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2023
Ultrabroadband reflective polarization convertor for terahertz waves
Publisher: AIP Publishing
Date: 03-11-2014
DOI: 10.1063/1.4901272
Fast Semi-Analytical Design for Single-FSS-Layer Circuit-Analog Absorbers
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
T-Ray Sensing and Imaging
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2007
Unclad Microphotonics for Terahertz Waveguides and Systems
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Fundamentals of Measurement in Terahertz Time-Domain Spectroscopy
Publisher: Springer Science and Business Media LLC
Date: 12-12-2013
Experimental demonstration of reflectarray antennas at terahertz frequencies
Publisher: The Optical Society
Date: 30-01-2013
DOI: 10.1364/OE.21.002875
Tutorial: Terahertz beamforming, from concepts to realizations
Publisher: AIP Publishing
Date: 06-02-2018
DOI: 10.1063/1.5011063
Abstract: The terahertz range possesses significant untapped potential for applications including high-volume wireless communications, noninvasive medical imaging, sensing, and safe security screening. However, due to the unique characteristics and constraints of terahertz waves, the vast majority of these applications are entirely dependent upon the availability of beam control techniques. Thus, the development of advanced terahertz-range beam control techniques yields a range of useful and unparalleled applications. This article provides an overview and tutorial on terahertz beam control. The underlying principles of wavefront engineering include array antenna theory and diffraction optics, which are drawn from the neighboring microwave and optical regimes, respectively. As both principles are applicable across the electromagnetic spectrum, they are reconciled in this overview. This provides a useful foundation for investigations into beam control in the terahertz range, which lies between microwaves and infrared light. Thereafter, noteworthy experimental demonstrations of beam control in the terahertz range are discussed, and these include geometric optics, phased array devices, leaky-wave antennas, reflectarrays, and transmitarrays. These techniques are compared and contrasted for their suitability in applications of terahertz waves.
Elastomeric silicone substrates for terahertz fishnet metamaterials
Publisher: AIP Publishing
Date: 06-02-2012
DOI: 10.1063/1.3665180
Abstract: In this work, we characterize the electromagnetic properties of polydimethylsiloxane (PDMS) and use this as a free-standing substrate for the realization of flexible fishnet metamaterials at terahertz frequencies. Across the 0.2–2.5 THz band, the refractive index and absorption coefficient of PDMS are estimated as 1.55 and 0–22 cm−1, respectively. Electromagnetic modeling, multi-layer flexible electronics microfabrication, and terahertz time-domain spectroscopy are used in the design, fabrication, and characterization of the metamaterials, respectively. The properties of PDMS add a degree of freedom to terahertz metamaterials, with the potential for tuning by elastic deformation or integrated microfluidics.
Flexible terahertz metamaterials for dual-axis strain sensing
Publisher: The Optical Society
Date: 11-06-2013
DOI: 10.1364/OL.38.002104
Metamaterial-based microfluidic sensor for dielectric characterization
Publisher: Elsevier BV
Date: 2013
Plasmonic Resonance toward Terahertz Perfect Absorbers
Publisher: American Chemical Society (ACS)
Date: 11-06-2014
DOI: 10.1021/PH500110T
Simple material parameter estimation via terahertz time-domain spectroscopy
Publisher: Institution of Engineering and Technology (IET)
Date: 2005
DOI: 10.1049/EL:20051467
Fabry-Pérot interferometer for sensing polar liquids at terahertz frequencies
Publisher: AIP Publishing
Date: 22-05-2017
DOI: 10.1063/1.4983780
Abstract: We propose and validate a sensor for polar liquids that operates in conjunction with terahertz time-domain spectroscopy. The sensor is constructed from an optically thick silicon wafer and a ground plane, separated by a gap into which the liquid is injected. This arrangement represents a Fabry-Pérot interferometer that causes a sharp minimum in the reflection spectrum. Compared to resonance-based sensors, this sensor design can maintain its sharp spectral response when loaded with highly absorbing polar liquids. This overcomes an issue of d ed resonance caused by material losses in resonance-based sensors. We report a reflection minimum shift of 8 GHz per percent ethanol in water. The sensor can be readily integrated with a microfluidic channel for real-time fluid monitoring.
Wideband Circularly Polarized 3-D Printed Dielectric Rod Antenna
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2020
Nanoscale TiO2 dielectric resonator absorbers
Publisher: The Optical Society
Date: 18-07-2016
DOI: 10.1364/OL.41.003391
Editorial Introduction to the Special Issue: Terahertz Metamaterials and Photonic Crystals
Publisher: Springer Science and Business Media LLC
Date: 26-07-2017
Compact Second-Order Bandstop Filter Based on Dual-Mode Complementary Split-Ring Resonator
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2016
Second-Order Terahertz Bandpass Frequency Selective Surface With Miniaturized Elements
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2015
Dual-mode behavior of the complementary electric-LC resonators loaded on transmission line: Analysis and applications
Publisher: AIP Publishing
Date: 26-08-2014
DOI: 10.1063/1.4893751
Abstract: This article presents an analysis of metamaterial resonators coupled with microstrip transmission line. The behavior of complementary electric-LC resonators loaded on a microstrip line is analyzed using the equivalent circuit model. In this paper, it is shown that a special type of these resonators show a dual-mode behavior when excited through the electromagnetic field around the microstrip transmission lines. The bandstop and bandpass configurations of these dual mode resonators loaded with microstrip lines are introduced and analyzed. Their potential applications are highlighted through designing a displacement sensor and a dual-mode bandpass filter prototypes.
Insulator-metal transition in substrate-independent VO2 thin film for phase-change devices
Publisher: Springer Science and Business Media LLC
Date: 20-12-2017
DOI: 10.1038/S41598-017-17937-3
Abstract: Vanadium has 11 oxide phases, with the binary VO 2 presenting stimuli-dependent phase transitions that manifest as switchable electronic and optical features. An elevated temperature induces an insulator–to–metal transition (IMT) as the crystal reorients from a monoclinic state (insulator) to a tetragonal arrangement (metallic). This transition is accompanied by a simultaneous change in optical properties making VO 2 a versatile optoelectronic material. However, its deployment in scalable devices suffers because of the requirement of specialised substrates to retain the functionality of the material. Sensitivity to oxygen concentration and larger-scale VO 2 synthesis have also been standing issues in VO 2 fabrication. Here, we address these major challenges in harnessing the functionality in VO 2 by demonstrating an approach that enables crystalline, switchable VO 2 on any substrate. Glass, silicon, and quartz are used as model platforms to show the effectiveness of the process. Temperature-dependent electrical and optical characterisation is used demonstrating three to four orders of magnitude in resistive switching, % chromic discrimination at infrared wavelengths, and terahertz property extraction. This capability will significantly broaden the horizon of applications that have been envisioned but remained unrealised due to the lack of ability to realise VO 2 on any substrate, thereby exploiting its untapped potential.
IEEE 802.15.3d-Compliant Waveforms for Terahertz Wireless Communications
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 15-12-2021
Horizontally Polarized 360° Beam-Steerable Frequency-Reconfigurable Antenna
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2019
Directional excitation of surface plasmons by dielectric resonators
Publisher: American Physical Society (APS)
Date: 27-02-2015
Single-FSS-Layer Absorber With Improved Bandwidth–Thickness Tradeoff Adopting Impedance-Matching Superstrate
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2019
Retrofittable antireflection coatings for T-rays
Publisher: Wiley
Date: 19-06-2007
DOI: 10.1002/MOP.22664
Effective-medium-cladded dielectric waveguides for terahertz waves
Publisher: The Optical Society
Date: 20-12-2019
DOI: 10.1364/OE.382181
Frequency-Selective-Surface-Based Mechanically Reconfigurable Terahertz Bandpass Filter
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2022
Assessing frost damage in barley using terahertz imaging
Publisher: Optica Publishing Group
Date: 29-09-2020
DOI: 10.1364/OE.404618
Abstract: Frost is estimated to cost Australian grain growers $ 360 million in direct and indirect losses every year. Assessing frost damage manually in barley is labor intensive and involves destructive s ling. To mitigate against significant economic loss, it is crucial that assessment decisions on whether to cut for hay or continue to harvest are made soon after frost damage has occurred. In this paper, we propose a non-destructive technique by using raster-scan terahertz imaging. Terahertz waves can penetrate the spike to determine differences between frosted and unfrosted grains. With terahertz raster-scan imaging, conducted in both transmission and reflection at 275 GHz, frosted and unfrosted barley spikes show significant differences. In addition, terahertz imaging allows to determine in idual grain positions. The emergence of compact terahertz sources and cameras would enable field deployment of terahertz non-destructive inspection for early frost damage.
Terahertz Reflectarrays and Nonuniform Metasurfaces
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2017
Quarter-wavelength multilayer interference filter for terahertz waves
Publisher: Elsevier BV
Date: 05-2008
Dual-mode terahertz time-domain spectroscopy system
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2013
High-$Q$ Terahertz Absorber With Stable Angular Response
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2020
Near-field interactions in electric inductive-capacitive resonators for metamaterials
Publisher: IOP Publishing
Date: 06-11-2012
DOI: 10.1088/0022-3727/45/48/485101
Abstract: Near-field interactions in an array of electric inductive–capacitive (ELC) resonators are investigated analytically, numerically and experimentally. The measurement and simulation results show that inter-cell coupling plays an important role in determining the response of metamaterials. A quasistatic dipole–dipole interaction model, together with a Lagrangian formalism, quantitatively explains the interplay between the electric and magnetic couplings in the resonator array. Depending on the alignment of the resonators, the couplings can cause resonance shifting and/or splitting. The knowledge obtained from this study is crucial in designing metamaterials with ELC resonators.
Tutorial on broadband transmissive metasurfaces for wavefront and polarization control of terahertz waves
Publisher: AIP Publishing
Date: 10-02-2022
DOI: 10.1063/5.0077652
Abstract: In order to harness the capabilities of terahertz waves, various metasurface-based functional devices have been developed recently. However, due to the limited usage of systematic optimization methodologies, many existing designs leave room for further bandwidth and efficiency improvement. This article provides an overview on the bandwidth limiting factors associated with metasurfaces and gives a tutorial on a semi-analytical approach to broadband design. The broadband approach incorporates network analysis and genetic algorithm to determine the frequency-independent optimal circuit parameters for multi-layer transmissive metasurfaces, so that targeted complex transmission coefficients can be achieved over a wide bandwidth. The broadband design approach is enabling the configuration and optimization of erse metasurfaces for wavefront and polarization control of terahertz waves, including quarter- and half-waveplates.
Frequency-Reconfigurable Circularly Polarized Omnidirectional Antenna
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2022
Terahertz Reflectarray with Enhanced Bandwidth
Publisher: Wiley
Date: 04-07-2019
Abstract: Reflectarrays offer unique potential for beamforming at terahertz frequencies as they combine the advantages of low‐profile of phased arrays and high‐efficiency of parabolic antennas. However, one challenge associated with reflectarrays is their bandwidth limitation resulting from the nonlinear phase response. To enhance bandwidth, a single‐layer stub‐loaded resonator is proposed for constructing reflectarrays. This resonator design shows a smooth and near‐linear phase response with a complete 360° phase coverage at and around the design frequency. To demonstrate its capability in realizing beamforming, a focusing reflectarray is then constructed using the proposed resonator as a building block. The measured results reveal that the 3 dB relative bandwidths of the reflectarray for the transverse electric (TE)‐ and transverse magnetic (TM)‐polarized excitations are 23.3% and 23.9%, respectively, while retaining an efficiency of 71.9% for the TE polarization and 71.0% for the TM polarization at the center frequency of 1.00 THz. The simulation bandwidth of this proposed focusing reflectarray is over twice that of an existing dielectric resonator reflectarray. The proposed resonator has a potential to enhance the bandwidth of terahertz reflectarrays for various beamforming functions.
Metamaterials in the Terahertz Regime
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2009
Broadband and wide-angle reflective linear polarization converter for terahertz waves
Publisher: AIP Publishing
Date: 09-2019
DOI: 10.1063/1.5116149
Hybrid metasurface for ultra-broadband terahertz modulation
Publisher: AIP Publishing
Date: 03-11-2014
DOI: 10.1063/1.4901050
Abstract: We demonstrate an ultra-broadband free-space terahertz modulator based on a semiconductor-integrated metasurface. The modulator is made of a planar array of metal cut-wires on a silicon-on-sapphire substrate, where the silicon layer functions as photoconductive switches. Without external excitation, the cut-wire array exhibits a Lorentzian resonant response with a transmission passband spanning dc up to the fundamental dipole resonance above 2 THz. Under photoexcitation with 1.55 eV near-infrared light, the silicon regions in the cut-wire gaps become highly conductive, causing a transition of the resonant metasurface to a wire grating with a Drude response. In effect, the low-frequency passband below 2 THz evolves into a stopband for the incident terahertz waves. Experimental validations confirm a bandwidth of at least 100%, spanning 0.5–1.5 THz with −10 dB modulation depth. This modulation depth is far superior to −5 dB achievable from a plain silicon-on-sapphire substrate with effectively 25 times higher pumping energy. The proposed concept of ultra-broadband metasurface modulator can be readily extended to electrically controlled terahertz wave modulation.
Ultra-wideband tri-layer transmissive linear polarization converter for terahertz waves
Publisher: AIP Publishing
Date: 04-2020
DOI: 10.1063/1.5144115
THz Systems Exploiting Photonics and Communications Technologies
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2023
1-to-N terahertz integrated switches enabling multi-beam antennas
Publisher: Optica Publishing Group
Date: 13-10-2023
All-silicon, low-cross-talk terahertz waveguide crossing based on effective medium
Publisher: Optica Publishing Group
Date: 29-10-2021
DOI: 10.1364/OL.436039
Abstract: All-silicon effective-medium-clad waveguides are a promising candidate for an integrated terahertz platform with high efficiency and broad bandwidth. Waveguide crossings are essential circuit components, allowing for wave routing over shorter paths to increase circuit density. However, the simple intersection of two orthogonal effective-medium-clad waveguides results in terahertz wave scattering, leading to relatively high cross talk. In this work, a low-loss, 40% fractional bandwidth crossing utilizing Maxwell–Garnet effective-medium theory and wavefront planarization techniques is proposed. This monolithic structure is fabricated on a single high-resistivity float-zone silicon wafer using a deep reactive ion etching process with a modest 4.4 mm diameter ( 4.03 λ 0 ) structure footprint. Experimentally verified results show low insertion loss, less than 1 dB, and average cross talk level of − 39 d B for both E 11 x and E 11 y operating modes, over 220–330 GHz with a 40% fractional bandwidth. This waveguide crossing can be foreseen as a useful routing component for terahertz all-silicon integrated circuits. The proposed techniques are applicable to other dielectric waveguide platforms at infrared and optical frequencies.
Compact electric-LC resonators for metamaterials
Publisher: The Optical Society
Date: 26-11-2010
DOI: 10.1364/OE.18.025912
Terahertz integration platforms using substrateless all-silicon microstructures
Publisher: AIP Publishing
Date: 09-2023
DOI: 10.1063/5.0158350
Effective-medium-clad Bragg grating filters
Publisher: AIP Publishing
Date: 07-2021
DOI: 10.1063/5.0051310
Abstract: We propose a series of integrated Bragg grating filters with performance enhancement via the concept of effective medium. The bandstop filters are built in a high-resistivity silicon wafer and operated over the WR-3.4 band (220–330 GHz) with in-plane polarization. The proposed designs use an additional degree of freedom in controlling the effective refractive index so as to fully use the potential of the Bragg grating structures. As a result, the high insertion loss typically observed at the low-frequency bound of the filters due to weak wave confinement can be reduced, while radiation caused by the leaky-wave effect at the high-frequency bound is minimized, allowing for a 40% operation fractional bandwidth. These features are not achievable with conventional waveguide Bragg grating filters. All-silicon prototypes of filter s les are experimentally validated, demonstrating promising performance for a wide range of terahertz applications. The techniques to improve the filter characteristics by controlling the effective medium can be adopted in both microwave and optics domains.
All-dielectric integration of dielectric resonator antenna and photonic crystal waveguide
Publisher: The Optical Society
Date: 19-06-2017
DOI: 10.1364/OE.25.014706
Spectral and angular characteristics of dielectric resonator metasurface at optical frequencies
Publisher: AIP Publishing
Date: 10-11-2014
DOI: 10.1063/1.4901735
Abstract: The capability of manipulating light at subwavelength scale has fostered the applications of flat metasurfaces in various fields. Compared to metallic structure, metasurfaces made of high permittivity low-loss dielectric resonators hold the promise of high efficiency by avoiding high conductive losses of metals at optical frequencies. This letter investigates the spectral and angular characteristics of a dielectric resonator metasurface composed of periodic sub-arrays of resonators with a linearly varying phase response. The far-field response of the metasurface can be decomposed into the response of a single grating element (sub-array) and the grating arrangement response. The analysis also reveals that coupling between resonators has a non-negligible impact on the angular response. Over a wide wavelength range, the simulated and measured angular characteristics of the metasurface provide a definite illustration of how different grating diffraction orders can be selectively suppressed or enhanced through antenna sub-array design.
Mechanically Tunable Dielectric Resonator Metasurfaces at Visible Frequencies
Publisher: American Chemical Society (ACS)
Date: 02-12-2016
Abstract: Devices that manipulate light represent the future of information processing. Flat optics and structures with subwavelength periodic features (metasurfaces) provide compact and efficient solutions. The key bottleneck is efficiency, and replacing metallic resonators with dielectric resonators has been shown to significantly enhance performance. To extend the functionalities of dielectric metasurfaces to real-world optical applications, the ability to tune their properties becomes important. In this article, we present a mechanically tunable all-dielectric metasurface. This is composed of an array of dielectric resonators embedded in an elastomeric matrix. The optical response of the structure under a uniaxial strain is analyzed by mechanical-electromagnetic co-simulations. It is experimentally demonstrated that the metasurface exhibits remarkable resonance shifts. Analysis using a Lagrangian model reveals that strain modulates the near-field mutual interaction between resonant dielectric elements. The ability to control and alter inter-resonator coupling will position dielectric metasurfaces as functional elements of reconfigurable optical devices.
Rapid detection of hairline cracks on the surface of piezoelectric ceramics
Publisher: Springer Science and Business Media LLC
Date: 03-04-2013
Dielectric resonator nanoantennas: A review of the theoretical background, design examples, prospects, and challenges
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2017
Material thickness optimization for transmission-mode terahertz time-domain spectroscopy
Publisher: Optica Publishing Group
Date: 06-05-2008
DOI: 10.1364/OE.16.007382
Abstract: The thickness of a s le material for a transmission-mode terahertz time-domain spectroscopy (THz-TDS) measurement is the subject of interest in this paper. A s le that is too thick or too thin can raise the problem of measurement uncertainty. Although greater thickness allows the terahertz radiation--or T-rays--to interact more with bulk material, the SNR rolls off with thickness due to signal attenuation. A s le that is too thin renders itself nearly invisible to T-rays, in such a way that the system can hardly sense the difference between the s le and a free space path. The optimal trade-off is analyzed and revealed in this paper, where our approach is to find the optimal thickness that results in the minimal uncertainty of measured optical constants. The derived model for optimal thickness is supported by the results from experiments performed with polyvinyl chloride (PVC), high-density polyethylene (HDPE), and lactose s les.
Terahertz reflectarray as a polarizing beam splitter
Publisher: The Optical Society
Date: 23-06-2014
DOI: 10.1364/OE.22.016148
Terahertz Magnetic Mirror Realized with Dielectric Resonator Antennas
Publisher: Wiley
Date: 09-10-2015
Abstract: Single-crystal silicon is bonded to a metal-coated substrate and etched in order to form an array of microcylinder passive terahertz dielectric resonator antennas (DRAs). The DRAs exhibit a magnetic response, and hence the array behaves as an efficient artificial magnetic conductor (AMC), with potential for terahertz antenna and sensing applications.
Terahertz plasmonic Bessel beamformer
Publisher: AIP Publishing
Date: 12-01-2015
DOI: 10.1063/1.4905445
Abstract: We experimentally demonstrate terahertz Bessel beamforming based on the concept of plasmonics. The proposed planar structure is made of concentric metallic grooves with a subwavelength spacing that couple to a point source to create tightly confined surface waves or spoof surface plasmon polaritons. Concentric scatterers periodically incorporated at a wavelength scale allow for launching the surface waves into free space to define a Bessel beam. The Bessel beam defined at 0.29 THz has been characterized through terahertz time-domain spectroscopy. This approach is capable of generating Bessel beams with planar structures as opposed to bulky axicon lenses and can be readily integrated with solid-state terahertz sources.
Ultrasensitive terahertz sensing with high-Q Fano resonances in metasurfaces
Publisher: AIP Publishing
Date: 27-10-2014
DOI: 10.1063/1.4895595
Abstract: High quality factor resonances are extremely promising for designing ultra-sensitive refractive index label-free sensors, since it allows intense interaction between electromagnetic waves and the analyte material. Metamaterial and plasmonic sensing have recently attracted a lot of attention due to subwavelength confinement of electromagnetic fields in the resonant structures. However, the excitation of high quality factor resonances in these systems has been a challenge. We excite an order of magnitude higher quality factor resonances in planar terahertz metamaterials that we exploit for ultrasensitive sensing. The low-loss quadrupole and Fano resonances with extremely narrow linewidths enable us to measure the minute spectral shift caused due to the smallest change in the refractive index of the surrounding media. We achieve sensitivity levels of 7.75 × 103 nm/refractive index unit (RIU) with quadrupole and 5.7 × 104 nm/RIU with the Fano resonances which could be further enhanced by using thinner substrates. These findings would facilitate the design of ultrasensitive real time chemical and biomolecular sensors in the fingerprint region of the terahertz regime.
Efficiency and Scalability of Dielectric Resonator Antennas at Optical Frequencies
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2014
A Review on Thin-film Sensing with Terahertz Waves
Publisher: Springer Science and Business Media LLC
Date: 03-2012
Distributed source model for the full-wave electromagnetic simulation of nonlinear terahertz generation
Publisher: The Optical Society
Date: 26-07-2012
DOI: 10.1364/OE.20.018397
Recent Progress in Terahertz Metasurfaces
Publisher: Springer Science and Business Media LLC
Date: 18-03-2017
Dielectric-resonator metasurfaces for broadband terahertz quarter- and half-wave mirrors
Publisher: The Optical Society
Date: 22-05-2018
DOI: 10.1364/OE.26.014392
Varactor-Tunable Second-Order Bandpass Frequency-Selective Surface With Embedded Bias Network
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2016
Demonstration of a highly efficient terahertz flat lens employing tri-layer metasurfaces
Publisher: The Optical Society
Date: 05-2017
DOI: 10.1364/OL.42.001867
Sub-diffraction thin-film sensing with planar terahertz metamaterials
Publisher: The Optical Society
Date: 27-01-2012
DOI: 10.1364/OE.20.003345
Dielectric resonator nanoantennas at visible frequencies
Publisher: The Optical Society
Date: 11-01-2013
DOI: 10.1364/OE.21.001344
High-Sensitivity Metamaterial-Inspired Sensor for Microfluidic Dielectric Characterization
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2014
Wideband Endfire 3-D-Printed Dielectric Antenna With Designable Permittivity
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2018
DIRECT FABRY-PÉROT EFFECT REMOVAL
Publisher: World Scientific Pub Co Pte Lt
Date: 06-2012
DOI: 10.1142/S0219477506003318
Abstract: This study indicates that the removal of reflections from T-ray signals can be carried out in the frequency domain without prior knowledge of material parameters or s le thickness. By fitting polynomials to the logarithm and the argument of the s le's transfer function, the Fabry-Pérot reflection term is canceled out, leading to disappearance of the reflections in spatial domain. The method successfully removes the reflections for optically thick s les under the condition of noise or litude fluctuations. The application to optically thin s les is possible when the s les are subjected to broadband terahertz measurements. The Fabry-Pérot free signal, when used as input to the parameter estimation method, results in correct material parameters with low variance.
Dielectric Resonator Reflectarray as High-Efficiency Nonuniform Terahertz Metasurface
Publisher: American Chemical Society (ACS)
Date: 19-05-2016
Integrated Silicon Photonic Crystals Toward Terahertz Communications
Publisher: Wiley
Date: 25-06-2018
Ultra-wideband far-infrared absorber based on anisotropically etched doped silicon
Publisher: Optica Publishing Group
Date: 24-02-2020
DOI: 10.1364/OL.382458
Abstract: Far-infrared absorbers exhibiting wideband performance are in great demand in numerous applications, including imaging, detection, and wireless communications. Here, a nonresonant far-infrared absorber with ultra-wideband operation is proposed. This absorber is in the form of inverted pyramidal cavities etched into moderately doped silicon. By means of a wet-etching technique, the crystallinity of silicon restricts the formation of the cavities to a particular shape in an angle that favors impedance matching between lossy silicon and free space. Far-infrared waves incident on this absorber experience multiple reflections on the slanted lossy silicon side walls, being dissipated towards the cavity bottom. The simulation and measurement results confirm that an absorption beyond 90% can be sustained from 1.25 to 5.00 THz. Furthermore, the experiment results suggest that the absorber can operate up to at least 21.00 THz with a specular reflection less than 10% and negligible transmission.
Practical method for determining inductance and capacitance of metamaterial resonators
Publisher: Institution of Engineering and Technology (IET)
Date: 2012
DOI: 10.1049/EL.2011.3547
High Frequency Properties and Applications of Elastomeric Silicones
Publisher: Wiley
Date: 18-04-2014
Terahertz transmissive half-wave metasurface with enhanced bandwidth
Publisher: Optica Publishing Group
Date: 20-08-2021
DOI: 10.1364/OL.431285
Abstract: Polarization conversion is useful for studies of chiral structures in biology and chemistry, and for polarization ersity in communications. It is conventionally realized with wave plates, which, however, present challenges due to limited material availability, as well as narrow bandwidth and low efficiency at terahertz frequencies. To enhance bandwidth and efficiency, the concept of the Huygens' metasurface is adopted here for a transmissive half-wave plate. The half-wave metasurface is designed following the optimal frequency-independent circuit parameters provided by a broadband semi-analytical approach. Simulation results of an optimal design suggest that a 15-dB extinction ratio can be sustained from 219 GHz to 334 GHz, corresponding to a fractional bandwidth of 41.6%. The measured results indicate that the fabricated structure enables a 15-dB extinction ratio from 220 GHz to 303 GHz, with a cross-polarization transmission efficiency above 76.7% for both linear and circular polarizations. This half-wave metasurface design can be readily integrated into compact terahertz systems for erse applications.
Modeling terahertz heating effects on water
Publisher: Optica Publishing Group
Date: 22-02-2010
DOI: 10.1364/OE.18.004727
Mechanically tunable terahertz metamaterials
Publisher: AIP Publishing
Date: 25-03-2013
DOI: 10.1063/1.4773238
Abstract: Electromagnetic device design and flexible electronics fabrication are combined to demonstrate mechanically tunable metamaterials operating at terahertz frequencies. Each metamaterial comprises a planar array of resonators on a highly elastic polydimethylsiloxane substrate. The resonance of the metamaterials is controllable through substrate deformation. Applying a stretching force to the substrate changes the inter-cell capacitance and hence the resonance frequency of the resonators. In the experiment, greater than 8% of the tuning range is achieved with good repeatability over several stretching-relaxing cycles. This study promises applications in remote strain sensing and other controllable metamaterial-based devices.
Terahertz near-field imaging of dielectric resonators
Publisher: The Optical Society
Date: 13-02-2017
DOI: 10.1364/OE.25.003756
Compressing onto a single pixel
Publisher: Springer Science and Business Media LLC
Date: 31-07-2014
Terahertz absorption: Photonic crystal traps THz waves
Publisher: Springer Science and Business Media LLC
Date: 31-07-2014
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