Abstract-Terahertz photoresponse of black phosphorus

Edward Leong, Ryan J. Suess, Andrei B. Sushkov, H. Dennis Drew, Thomas E. Murphy, and Martin Mittendorff

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-11-12666

Two-dimensional black phosphorus is a new material that has gained widespread interest as an active material for optoelectronic applications. It features high carrier mobility that allows for efficient free-carrier absorption of terahertz radiation, even though the photon energy is far below the bandgap energy. Here we present an efficient and ultrafast terahertz detector, based on exfoliated multilayer flakes of black phosphorus. The device responsivity is about 1 mV/W for a 2.5 THz beam with a diameter of 200 μm, and is primarily limited by the small active area of the device in comparison to the incident beam area. The intrinsic responsivity is determined by Joule heating experiments to be about 44 V/W, which is in agreement with predictions from the Drude conductivity model. Time resolved measurements at a frequency of 0.5 THz reveal an ultrafast response time of 20 ps, making black phosphorus a candidate for high performance THz detection at room temperature.

© 2017 Optical Society of America

Abstract-Terahertz Nonlinearity in Graphene Plasmons

Mohammad M. Jadidi, Jacob C. König-Otto, Stephan Winnerl, Andrei B. Sushkov, H. Dennis Drew, Thomas E. Murphy, Martin Mittendorff

http://arxiv.org/abs/1512.07508
Sub-wavelength graphene structures support localized plasmonic resonances in the terahertz and mid-infrared spectral regimes. The strong field confinement at the resonant frequency is predicted to significantly enhance the light-graphene interaction, which could enable nonlinear optics at low intensity in atomically thin, sub-wavelength devices. To date, the nonlinear response of graphene plasmons and their energy loss dynamics have not been experimentally studied. We measure and theoretically model the terahertz nonlinear response and energy relaxation dynamics of plasmons in graphene nanoribbons. We employ a THz pump-THz probe technique at the plasmon frequency and observe a strong saturation of plasmon absorption followed by a 10 ps relaxation time. The observed nonlinearity is enhanced by two orders of magnitude compared to unpatterned graphene with no plasmon resonance. We further present a thermal model for the nonlinear plasmonic absorption that supports the experimental results.

Abstract-Hybrid Metal-Graphene Plasmons for Tunable Terahertz Optoelectronics

Mohammad M. Jadidi, Andrei B. Sushkov, Rachael L. Myers-Ward, Anthony K. Boyd, Kevin M. Daniels, D.Kurt Gaskill, Michael S. Fuhrer, H.Dennis Drew, Thomas E. Murphy

(Submitted on 18 Jun 2015)

http://xxx.tau.ac.il/abs/1506.05817

Graphene has unique and advantageous electronic and optical properties, especially in the underdeveloped terahertz range of the electromagnetic spectrum. Sub-micron graphene structures support terahertz (THz) plasmonic resonances that can be tuned by applying a gate voltage. Because these plasmonic structures are sub-wavelength in size, they need to be integrated with a THz antenna or a metamaterial structure to optimize the graphene coupling to the free space radiation. Furthermore, nearly all THz optoelectronic applications including detectors, filters, and modulators require electrical connection or antenna coupling to the graphene, which inhibits the accumulation of charge at the edges of the graphene. Here, we present the first observation and systematic study of plasmon resonances in a hybrid graphene-metal design in which the graphene acts as a gate-tuneable inductor, and metal as a capacitive reservoir for charge accumulation. We experimentally demonstrate a large resonant absorption in low-mobility graphene (μ=1000 cm2V−1s−1), and show that the peak can approach 100% in an optimized device, ideal for graphene-based THz detectors. We predict that use of high mobility graphene (μ>50000 cm2V−1s−1) will allow resonant THz transmission near 100%, realizing a near perfect tunable THz filter or modulator.

Abstract-Plasmon-enhanced Terahertz Photodetection in Graphene

Xinghan Cai , Andrei B. Sushkov , Mohammad M. Jadidi , Luke O Nyakiti , Rachael L. Myers-Ward , D Kurt Gaskill , Thomas E. Murphy , Michael S Fuhrer , and H. Dennis Drew

Nano Lett., Just Accepted Manuscript

DOI: 10.1021/acs.nanolett.5b00137

Publication Date (Web): April 14, 2015

Copyright © 2015 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.5b00137

We report a large area terahertz detector utilizing a tunable plasmonic resonance in sub-wavelength graphene micro-ribbons on SiC(0001) to increase the absorption efficiency. By tailoring the orientation of the graphene ribbons with respect to an array of sub-wavelength bimetallic electrodes, we achieve a condition in which the plasmonic mode can be efficiently excited by an incident wave polarized perpendicular to the electrode array, while the resulting photothermal voltage can be observed between the outermost electrodes.

Abstract-Sensitive Room-Temperature Terahertz Detection via Photothermoelectric Effect in Graphene

Xinghan Cai, Andrei B. Sushkov, Ryan J. Suess, Mohammad M. Jadidi, Greg S. Jenkins, Luke O. Nyakiti, Rachael L. Myers-Ward, Jun Yan, D. Kurt Gaskill, Thomas E. Murphy, H. Dennis Drew,Michael S. Fuhrer

(Submitted on 14 May 2013 (v1), last revised 7 Nov 2013 (this version, v2))

http://arxiv.org/abs/1305.3297

Terahertz (THz) radiation has uses from security to medicine, however sensitive room-temperature detection of THz is notoriously difficult. The hot-electron photothermoelectric effect in graphene is a promising solution: 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. Here we demonstrate a graphene thermoelectric THz photodetector with sensitivity exceeding 100 V/W at room temperature and noise equivalent power (NEP) less than 100 pW/Hz1/2, competitive with the best room-temperature THz detectors, while time-resolved measurements indicate our graphene detector is eight to nine orders of magnitude faster. A simple model of the response, including contact asymmetries (resistance, work function and Fermi-energy pinning) reproduces the qualitative features of the data, and indicates that orders-of-magnitude sensitivity improvements are possible.

Abstract-Sensitive Room-Temperature Terahertz Detection via Photothermoelectric Effect in Graphene

http://arxiv.org/abs/1305.3297
 Xinghan Cai, Andrei B. Sushkov, Ryan J. Suess, Greg S. Jenkins, Jun Yan, Thomas E. Murphy, H. Dennis Drew, Michael S. Fuhrer

Terahertz (THz) radiation has uses from security to medicine, however sensitive room-temperature detection of THz is notoriously difficult. The hot-electron photothermoelectric effect in graphene is a promising solution: 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. Here we demonstrate a graphene thermoelectric THz photodetector with sensitivity exceeding 100 V/W at room temperature and noise equivalent power (NEP) less than 100 pW/Hz^1/2, competitive with the best room-temperature THz detectors, while time-resolved measurements on similar devices indicate our graphene detector is more than seven orders of magnitude faster. A simple model of the response, including contact asymmetries (resistance, work function and Fermi-energy pinning) reproduces the qualitative features of the data, and indicates that orders-of-magnitude sensitivity improvements are possible.