Abstract-Enhancing THz generation in photomixers using a metamaterial approach

Daniel J. Ironside, Rodolfo Salas, Pai-Yen Chen, Khai Q. Le, Andrea Alú, and Seth R. Bank

Fig. 1 As illustration depicting key photomixer design features between (a) the conventional photomixer design and (b) the proposed enhanced metamaterial design.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-7-9481

Photomixers at THz frequencies offer an attractive solution to fill the THz gap; however, conventional photomixer designs result in low output powers, on the order of microwatts, before thermal failure. We propose an alternative photomixer design capable of orders of magnitude enhancement of continuous-wave THz generation using a metamaterial approach. By forming a metal-semiconductor-metal (MSM) cavity through layering an ultrafast semiconductor material between subwavelength metal-dielectric gratings, tailored resonance can achieve ultrathin absorbing regions and efficient heat sinking. When mounted to a tunable E-patch antenna, gratings also act as vertically biased electrodes, further enhancing photoconductive gain by reducing the carrier path length to nanoscales. Thus, through these multiplicative enhancements, the metamaterial-enhanced photomixer is projected to generate THz powers in the milliwatt range and exceed the Manley-Rowe limit for frequencies less than 2 THz.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Graphene metascreen for designing compact infrared absorbers with enhanced bandwidth

Pai-Yen Chen1, Mohamed Farhat2 and Hakan Bağcı2
http://iopscience.iop.org/0957-4484/26/16/164002

pychen@wayne.edu mohamed.farhat@kaust.edu.sa

1 Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI 48202, USA
2 Division of Computer, Electrical, and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia 

We propose a compact, wideband terahertz and infrared absorber, comprising a patterned graphene sheet on a thin metal-backed dielectric slab. This graphene-based nanostructure can achieve a low or negative effective permeability, necessary for realizing the perfect absorption. The dual-reactive property found in both the plasmonic graphene sheet and the grounded high-permittivity slab introduces extra poles into the equivalent circuit model of the system, thereby resulting in a dual-band or broadband magnetic resonance that enhances the absorption bandwidth. More interestingly, the two-dimensional patterned graphene sheet significantly simplifies the design and fabrication processes for achieving resonant magnetic response, and allows the frequency-reconfigurable operation via electrostatic gating.

Abstract-A Graphene-Based Plasmonic Platform for Reconfigurable Terahertz Nanodevices

Pai-Yen Chen , Haiyu Huang , Deji Akinwande , and Andrea Alu

http://pubs.acs.org/doi/abs/10.1021/ph500046r


We propose here a new platform to realize a plethora of graphene-based plasmonic nanodevices for frequency-agile terahertz (THz) frontend circuits. We demonstrate that a class of hybrid electronic-plasmonic nanodevices combining active graphene field-effect transistors (GFET) and graphene plasmonic waveguides (GPWG) supporting tightly-confined propagation of THz signals, with tailored phase velocity and characteristic impedance controlled by the gate and drain voltages of GFET. We propose a variety of reconfigurable graphene-based nanodevices based on this general architecture, including reconfigurable and electronically-programmable phase-shifters, filters, impedance transformers, modulators, and terminators. We envision the integration of these active THz circuit elements into a fully reconfigurable THz system as a fundamental step towards new design architectures and protocols for THz communication, sensing, actuation, and biomedical applications.

Abstract -Nanostructured graphene metasurface for tunable terahertz cloaking

Pai-Yen Chen1, Jason Soric1, Yashwanth R Padooru2, Hossein M Bernety2, Alexander B Yakovlev2 and Andrea Alù1,3

http://iopscience.iop.org/1367-2630/15/12/123029/article;jsessionid=CFFC252A066AB15BD39AA849D2CEA0DF.c1

alu@mail.utexas.edu

1 Department of Electrical and Computer Engineering, University of Texas at Austin, Austin, TX 78712, USA
2 Center for Applied Electromagnetic Systems Research (CAESR), Department of Electrical Engineering, The University of Mississippi, University, MS 38677-1848, USA
3 Author to whom any correspondence should be addressed. 

Pai-Yen Chen et al 2013 New J. Phys. 15 123029
doi:10.1088/1367-2630/15/12/123029
© IOP Publishing and Deutsche Physikalische Gesellschaft
Received 20 July 2013
Published 17 December 2013

We propose and analyze a graphene-based cloaking metasurface aimed at achieving widely tunable scattering cancelation in the terahertz (THz) spectrum. This 'one-atom-thick' mantle cloak is realized by means of a patterned metasurface comprised of a periodic array of graphene patches, whose surface impedance can be modeled with a simple yet accurate analytical expression. By adjusting the geometry and Fermi energy of graphene nanopatches, the metasurface reactance may be tuned from inductive to capacitive, as a function of the relative kinetic inductance and the geometric patch capacitance, enabling the possibility of effectively cloaking both dielectric and conducting objects at THz frequencies with the same metasurface. We envision applications for low-observable nanostructures and efficient THz sensing, routing and detection.

Paper-A terahertz photomixer based on plasmonic nanoantennas coupled to a graphene emitter

Pai-Yen Chen¹ and Andrea Alù
http://iopscience.iop.org/0957-4484/24/45/455202;jsessionid=662617F0AD91E1046CDC2A989905027D.c2

pychen@utexas.edu alu@mail.utexas.edu
Department of Electrical and Computer Engineering, The University of Texas at Austin, 1 University Station C0803, Austin, TX 78712, USA

We propose the concept of a graphene-based nanoantenna-enhanced photomixer to realize wideband-tunable terahertz (THz) frequency generation. When two laser beams are focused on the graphene nanoemitter of a planar field-emission diode, THz current oscillations can be created at the emitter tip through the optical heterodyne. Graphene's optical transparency allows suitably designed plasmonic nanoantennas to boost the mixing of laser radiation at the emitter tip, significantly increasing the overall produced photomixing current. The THz wave generated at the graphene emitter is then coupled to a loading circuit, thanks to the THz wave confinement in the graphene nanostructures. Our design is ideally suited for THz sources that may be tuned from DC to 10 THz by simply shifting the frequency offset of two pumping lasers.