Abstract- Antenna Integrated THz Uni-Traveling Carrier Photodiodes

Cyril C. Renaud, Michele Natrella,   Chris Graham,  James Seddon,   Frederic Van Dijk,  Alwyn J. Seeds

http://ieeexplore.ieee.org/document/7979505/

High-speed photodiodes are a key element of numerous photonic systems. With the development of potential applications in the THz range such as sensing, spectroscopy, and wireless transmission, devices with integrated antenna covering the frequency range from 0.1 to 3 THz will become essential. In this paper, we discuss the development of uni-traveling carrier photodiodes with integrated antennas to address that need. In particular we develop the key elements to present a simple design tool for the efficient integration of the device with an antenna. We also present fabricated device results that show the highest figure of merit to date for photonic THz emitters. When integrated with well-matched antennas the devices have achieved record level of power up to 1 THz compared to other published photomixers. We also show that these devices can be used as receivers at frequencies up to 560 GHz with conversion losses of the order of 30 dB.

Abstract-Resonant terahertz probes for near-field scattering microscopy

Thomas Siday, Michele Natrella, Jiang Wu, Huiyun Liu, and Oleg Mitrofanov

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-22-27874


We propose and characterize a scattering probe for terahertz (THz) near-field microscopy, fabricated from indium, where the scattering efficiency is enhanced by the dipolar resonance supported by the indium probe. The scattering properties of the probe were evaluated experimentally using THz time-domain spectroscopy (TDS), and numerically using the finite-difference time-domain (FDTD) method in order to identify resonant enhancement. Numerical measurements show that the indium probes exhibit enhanced scattering across the THz frequency range due to dipolar resonance, with a fractional bandwidth of 0.65 at 1.24 THz. We experimentally observe the resonant enhancement of the scattered field with a peak at 0.3 THz. To enable practical THz microscopy applications of these resonant probes, we also demonstrate a simple excitation scheme utilizing a THz source with radial polarization, which excites a radial mode along the length of the tip. Strong field confinement at the apex of the tip, as required for THz near-field microscopy, was observed experimentally.

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.

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

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-9-10177

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.

Abstract-Accurate equivalent circuit model for millimetre-wave UTC photodiodes

Michele Natrella, Chin-Pang Liu, Chris Graham, Frederic van Dijk, Huiyun Liu, Cyril C. Renaud, and Alwyn J. Seeds
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-5-4698

We present a comprehensive study of uni-travelling carrier photodiode impedance and frequency photo-response supported by measurements up to 110 GHz. The results of this investigation provide valuable new information for the optimisation of the coupling efficiency between UTC-PDs and THz antennas. We show that the measured impedance cannot be explained employing the standard junction-capacitance/series-resistance concept and propose a new model for the observed effects, which exhibits good agreement with the experimental data. The achieved knowledge of the photodiode impedance will allow the absolute level of power emitted by antenna integrated UTCs to be predicted and ultimately maximized.

© 2016 Optical Society of America

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Abstract-Coherent terahertz photonics

 

 

 

Alwyn J. Seeds, Martyn J. Fice, Katarzyna Balakier, Michele Natrella, Oleg Mitrofanov, Marco Lamponi, Mourad Chtioui, Frederic van Dijk, Michael Pepper, Gabriel Aeppli, A. Giles Davies, Paul Dean, Edmund Linfield, and Cyril C. Renaud

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-21-19-22988

We present a review of recent developments in THz coherent systems based on photonic local oscillators. We show that such techniques can enable the creation of highly coherent, thus highly sensitive, systems for frequencies ranging from 100 GHz to 5 THz, within an energy efficient integrated platform. We suggest that such systems could enable the THz spectrum to realize its full applications potential. To demonstrate how photonics-enabled THz systems can be realized, we review the performance of key components, show recent demonstrations of integrated platforms, and give examples of applications.

© 2013 OSA