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SUMMARY:Fast Terahertz Optoelectronic Amplitude Modulator Based on Plasmon
 ic Metamaterial Antenna Arrays and Graphene (SP Workshop) - Mr David Jesso
 p\, University of Cambridge\, Semiconductor Physics Group
DTSTART:20160203T141500Z
DTEND:20160203T151500Z
UID:TALK60991@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:The growing interest in terahertz (THz) technologies in recent
  years has seen a wide range of demonstrated applications\, spanning from 
 security screening\, non-destructive testing\, gas sensing\, to biomedical
  imaging and communication. Communication with THz radiation offers the ad
 vantage of much higher bandwidths than currently available\, in an unalloc
 ated spectrum. For this to be realized\, optoelectronic components capable
  of manipulating THz radiation at high speeds and high signal-to-noise rat
 ios must be developed. In this work we demonstrate a room temperature freq
 uency dependent optoelectronic amplitude modulator working at around 2 THz
 \, which incorporates graphene as the tuning medium. The architecture of t
 he modulator is an array of plasmonic dipole antennas surrounded by graphe
 ne. By electrostatically doping the graphene via a back gate electrode\, t
 he reflection characteristics of the modulator are modified. The modulator
  is electrically characterized to determine the graphene conductivity and 
 optically characterization\, by THz time-domain spectroscopy and a single-
 mode 2 THz quantum cascade laser\, to determine the optical modulation dep
 th and cut-off frequency. A maximum optical modulation depth of ~30% is es
 timated and is found to be most (least) sensitive when the electrical modu
 lation is centered at the point of maximum (minimum) differential resistiv
 ity of the graphene. A 3 dB cut-off frequency > 5 MHz\, limited only by th
 e area of graphene on the device\, is reported. The results agree well wit
 h theoretical calculations and numerical simulations\, and demonstrate the
  first steps towards ultra-fast\, graphene based THz optoelectronic device
 s.
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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