May 13, 2016

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, ACS Photonics, online May 13, 2016, DOI: 10.1021/acsphotonics.6b00102

The terahertz spectral range has significant potential for applications, including communications, noninvasive medical imaging for cancer diagnosis, security screening, and pharmaceutical quality control. 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, a metasurface composed of nonuniform dielectric resonator antennas on a ground plane is used 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 for attaining high efficiency. The capacity of the reflectarray 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 device demonstrated can therefore be deployed for high-gain terahertz antennas. Further measurements indicate that the losses of the reflectarray are negligible, which confirms the high efficiency of the dielectric resonators. This finding will support the design of efficient flat-profile terahertz reflectarrays and metasurfaces to serve as arbitrary beam control requirements in the near- and far-field.

The scientific and technical impact of the study can be summarized as:

  • A high-efficiency reflectarray antenna that operates in the terahertz range has been experimentally demonstrated; this region of the spectrum has unique features that make it very suitable for applications such as noninvasive medical imaging for cancer diagnosis, security screening, and communications.
  • The flat-profile antenna can be used to control the reflected beam according to requirements in both the near- and far-field with negligible losses, a very desirable feature at such frequencies.
  • The antenna, designed as a proof-of-concept for operation as an off-axis focusing mirror, opens opportunities for design of more advanced devices for use in the terahertz range, such as holograms and anisotropic devices for beam-forming and polarization control applications.
  • Such efficient and versatile devices are expected to make a significant impact across broad fields of terahertz technology.