CME Seminar - Thursday, November 20th - Dennis Drew, CNAM, University of Maryland

[Longbrake, Patricia]

Please join us for the Condensed Matter Experiment Seminar presented by Dennis Drew, CNAM, University of Maryland on Thursday, November 20th at 11:30am in the Smith Seminar Room (1080 PRB).

TITLE:  "THz detectors and emitters with graphene devices"

ABSTRACT:  Terahertz (THz) radiation has important uses from security to medicine, however the THz spectral range is notoriously underdeveloped because of the lack of room temperature sources and detectors. As a result little technology exists for this otherwise attractive ultrahigh frequency band. I will describe recent work suggests that graphene, a single atom thick carbon honeycomb lattice, may be the key to a robust THz technology. Graphene has a gapless Dirac electronic spectrum and a strong specific coupling to light. The gapless character implies optical coupling at all frequencies. Moreover, doped graphene exhibits plasmonic charge density waves that allow resonant excitation in micron sized samples with THz radiation.

We have demonstrated room temperature THz detectors that operate on the hot‐electron photothermoelectric effect in graphene.  Photoexcited carriers rapidly thermalize due to strong electron-electron interactions, but lose energy to the lattice more slowly. The electron temperature gradient drives electron diffusion, and asymmetry due to local gating or dissimilar contact metals produces a net current via the thermoelectric effect. The performance is competitive with the best room‐temperature THz detectors for an optimally coupled device, while time‐resolved measurements show that our graphene detector is eight to nine orders of magnitude faster.

We are currently studying THz emission based on the hot electron effect.  By mixing two NIR laser signals on graphene elements with a frequency difference in the THz range the photo-thermo-electric effect can be used to excite plasma resonances.  The excited plasmons are then coupled to the far field with an antenna.

If you would like to meet with Dr. Drew during his visit, please contact me for available times.

Thank you,
Trisch
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