Abstract-Broadband Terahertz Circular-Polarization Beam Splitter

Wendy S. L. Lee, Shruti Nirantar, Daniel Headland, Madhu Bhaskaran, Sharath Sriram, Christophe Fumeaux, Withawat Withayachu

http://onlinelibrary.wiley.com/doi/10.1002/adom.201700852/full

Splitting circularly polarized waves is desirable for high-data-rate wireless communications and study of molecular chirality at terahertz frequencies. Typically, this functionality is achieved using bulk optical systems with limitations in material availability, bandwidth, and efficiency. As an alternative, metasurfaces with spatially varying broadband birefringence are employed to attain the same functionality. It is demonstrated that a metasurface designed with gradually rotated birefringent resonators can deflect normally incident left-handed circularly polarized and right-handed circularly polarized waves into different directions. This beam splitting functionality is maintained over an experimentally demonstrated relative deflection bandwidth of 53%, namely, covering the band of 0.58–1.00 THz.

Abstract-Terahertz near-field imaging of dielectric resonators

Wendy S. L. Lee, Korbinian Kaltenecker, Shruti Nirantar, Withawat Withayachumnankul, Markus Walther, Madhu Bhaskaran, Bernd M. Fischer, Sharath Sriram, and Christophe Fumeaux

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-4-3756

As an alternative to metallic resonators, dielectric resonators can increase radiation efficiencies of metasurfaces at terahertz frequencies. Such subwavelength resonators made from low-loss dielectric materials operate on the basis of oscillating displacement currents. For full control of electromagnetic waves, it is essential that dielectric resonators operate around their resonant modes. Thus, understanding the nature of these resonances is crucial towards design implementation. To this end, an array of silicon resonators on a quartz substrate is designed to operate in transmission at terahertz frequencies. The resonator dimensions are tailored to observe their low-order modes of resonance at 0.58 THz and 0.61 THz respectively. We employ a terahertz near-field imaging technique to measure the complex near-fields of this dielectric resonator array. This unique method allows direct experimental observation of the first two fundamental resonances.

© 2017 Optical Society of America

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Abstract-Dielectric Resonator Reflectarray as High-Efficiency Nonuniform Terahertz Metasurface

Daniel Headland*†, Eduardo Carrasco‡¶, Shruti Nirantar§∥, Withawat Withayachumnankul†⊥, Philipp Gutruf§∥,James Schwarz§∥, Derek Abbott†, Madhu Bhaskaran§∥, Sharath Sriram§∥, Julien Perruisseau-Carrier‡, and Christophe Fumeaux†

† School of Electrical and Electronic Engineering, The University of Adelaide, Adelaide, SA 5005, Australia

‡ École Polytechnique Fédérale de Lausanne, EPFL, 1015 Lausanne, Switzerland

¶ Foundation for Research on Information Technologies in Society, IT’IS, 8004 Zürich, Switzerland

§Functional Materials and Microsystems Research Group and ∥MicroNano Research Facility, RMIT University, Melbourne, Victoria 3000, Australia

⊥ Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan

ACS Photonics, Article ASAP

DOI: 10.1021/acsphotonics.6b00102

Publication Date (Web): May 13, 2016

Copyright © 2016 American Chemical Society

*E-mail: daniel.headland@adelaide.edu.au.

http://pubs.acs.org/doi/abs/10.1021/acsphotonics.6b00102

Advances in terahertz technology rely on the combination of novel materials and designs. As new devices are demonstrated to address the terahertz gap, the ability to perform high-efficiency beam control will be integral to making terahertz radiation a practical technology. Here, we use a metasurface composed of nonuniform dielectric resonator antennas on a ground plane to achieve efficient beam focusing at 1 THz. The dielectric resonators are made of high-resistivity silicon, which is a low-loss, nondispersive material for terahertz waves. The resonators operate around the resonance of the displacement current in the silicon, which is crucial to attaining high efficiency. The reflectarray’s capacity to focus terahertz radiation is experimentally verified, and hence by the principle of antenna reciprocity, it can also be employed as a terahertz collimator. The demonstrated device can therefore be deployed for high-gain terahertz antennas. Further measurements show that the loss of the reflectarray is negligible, which confirms the high efficiency of the dielectric resonators. This finding will enable the design of efficient flat-profile terahertz reflectarrays and metasurfaces to serve arbitrary beam control requirements in the near and far fields.

Abstract-Dielectric resonator reflectarray as high-efficiency non-uniform terahertz metasurface

Daniel Headland, Eduardo Carrasco, Shruti Nirantar, Withawat Withayachumnankul, Philipp Gutruf, James Schwarz, Derek Abbott, Madhu Bhaskaran, Sharath Sriram, Julien Perruisseau-Carrier, and Christophe Fumeaux

ACS Photonics, Just Accepted Manuscript

DOI: 10.1021/acsphotonics.6b00102

Publication Date (Web): May 13, 2016

Copyright © 2016 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acsphotonics.6b00102

Abstract

Advances in terahertz technology rely on the combination of novel materials and designs. As new devices are demonstrated to address the terahertz gap, the ability to perform high-efficiency beam control will be integral to making terahertz a practical technology. Here, we use a metasurface composed of nonuniform dielectric resonator antennas on a ground plane to achieve efficient beam focusing at 1 THz. The dielectric resonators are made of high-resistivity silicon, which is a low-loss, non-dispersive material for terahertz waves. The resonators operate around the resonance of displacement current in the silicon, which is crucial to attaining high-efficiency. The reflectarray’s capacity to focus terahertz radiation is experimentally verified, and hence by the principle of antenna reciprocity, it can also be employed as a terahertz collimator. The demonstrated device can therefore be deployed for high-gain terahertz antennas. Further measurements show that the loss of the reflectarray is negligible, which confirms the high efficiency of the dielectric resonators. This finding will enable the design of efficient flat-profile terahertz reflectarrays and metasurfaces to serve arbitrary beam control requirements in the near- and far-field.

Abstract-Terahertz Magnetic Mirror Realized with Dielectric Resonator Antennas

1. Daniel Headland¹, 
2. Shruti Nirantar^2,3,
3. Withawat Withayachumnankul^1,2,4, 
4. Philipp Gutruf^2,3, 
5. Derek Abbott¹, 
6. Madhu Bhaskaran^2,3, 
7. Christophe Fumeaux^1,*and
8. Sharath Sriram^2,3,*

Article first published online: 9 OCT 2015

DOI: 10.1002/adma.201503069

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

http://onlinelibrary.wiley.com/doi/10.1002/adma.201503069/abstract;jsessionid=5E1D330CB11C192A553C5E4A3AC815B7.f04t02?userIsAuthenticated=false&deniedAccessCustomisedMessage=

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.