Friday, April 28, 2017

Abstract-Terahertz generation mechanism in nano-grating electrode photomixers on Fe-doped InGaAsP

Reshma A. Mohandas, Joshua R. Freeman, Michele Natrella, Mark C. Rosamond, Lalitha Ponnampalam, Martyn J. Fice, Alwyn J. Seeds, Paul. J. Cannard, Michael. J. Robertson, David. G. Moodie, A. Giles Davies, Edmund H. Linfield, and Paul Dean

We report the generation mechanism associated with nano-grating electrode photomixers fabricated on Fe-doped InGaAsP substrates. Two different emitter designs incorporating nano-gratings coupled to the same broadband antenna were characterized in a continuous-wave terahertz (THz) frequency system employing telecommunications wavelength lasers for generation and coherent detection. The current-voltage characteristics and THz emission bandwidth of the emitters is compared for different bias polarities and optical polarisations. The THz output from the emitters is also mapped as a function of the position of the laser excitation spot for both continuous-wave and pulsed excitation. This mapping, together with full-wave simulations of the structures, confirms the generation mechanism to be due to an enhanced optical electric field at the grating tips resulting in increased optical absorption, coinciding with a concentration of the electrostatic field.
Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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