Abstract-Terahertz ratchet effects in graphene with a lateral superlattice

P. Olbrich, J. Kamann, M. König, J. Munzert, L. Tutsch, J. Eroms, D. Weiss, Ming-Hao Liu (劉明豪), L. E. Golub, E. L. Ivchenko, V. V. Popov, D. V. Fateev, K. V. Mashinsky, F. Fromm, Th. Seyller, and S. D. Ganichev

Phys. Rev. B 93, 075422 – Published 12 February 2016

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.075422

Experimental and theoretical studies on ratchet effects in graphene with a lateral superlattice excited by alternating electric fields of terahertz frequency range are presented. A lateral superlattice deposited on top of monolayer graphene is formed either by periodically repeated metal stripes having different widths and spacings or by interdigitated comblike dual-grating-gate (DGG) structures. We show that the ratchet photocurrent excited by terahertz radiation and sensitive to the radiation polarization state can be efficiently controlled by the back gate driving the system through the Dirac point as well as by the lateral asymmetry varied by applying unequal voltages to the DGG subgratings. The ratchet photocurrent includes the Seebeck thermoratchet effect as well as the effects of “linear” and “circular” ratchets, sensitive to the corresponding polarization of the driving electromagnetic force. The experimental data are analyzed for the electronic and plasmonic ratchets taking into account the calculated potential profile and the near field acting on carriers in graphene. We show that the photocurrent generation is based on a combined action of a spatially periodic in-plane potential and the spatially modulated light due to the near-field effects of the light diffraction.

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Abstract-Terahertz ratchet effects in graphene with a lateral superlattice

P. Olbrich, J. Kamann, M. König, J. Munzert, L. Tutsch, J. Eroms, D.Weiss, Ming-Hao Liu, L.E. Golub, E.L. Ivchenko, V.V.Popov, D.V. Fateev, K.V. Mashinsky, F. Fromm, Th. Seyller, S.D. Ganichev

http://arxiv.org/abs/1510.07946

Experimental and theoretical studies on ratchet effects in graphene with a lateral superlattice excited by alternating electric fields of terahertz frequency range are presented. A lateral superlatice deposited on top of monolayer graphene is formed either by periodically repeated metal stripes having different widths and spacings or by inter-digitated comb-like dual-grating-gate (DGG) structures. We show that the ratchet photocurrent excited by terahertz radiation and sensitive to the radiation polarization state can be efficiently controlled by the back gate driving the system through the Dirac point as well as by the lateral asymmetry varied by applying unequal voltages to the DGG subgratings. The ratchet photocurrent includes the Seebeck thermoratchet effect as well as the effects of "linear" and "circular" ratchets, sensitive to the corresponding polarization of the driving electromagnetic force. The experimental data are analyzed for the electronic and plasmonic ratchets taking into account the calculated potential profile and the near field acting on carriers in graphene. We show that the photocurrent generation is based on a combined action of a spatially periodic in-plane potential and the spatially modulated light due to the near field effects of the light diffraction.

Abstract-Helicity sensitive terahertz radiation detection by dual-grating-gate high electron mobility transistors

P. Faltermeier¹, P. Olbrich¹, W. Probst¹, L. Schell¹, T. Watanabe², S. A. Boubanga-Tombet², T. Otsuji² and S. D. Ganichev¹
http://scitation.aip.org/content/aip/journal/jap/118/8/10.1063/1.4928969
1 Terahertz Center, University of Regensburg, 93040 Regensburg, Germany
2 Research Institute of Electrical Communication, Tohoku University, 980-8577 Sendai, Japan
J. Appl. Phys. 118, 084301 (2015); http://dx.doi.org/10.1063/1.4928969

We report on the observation of a radiation helicity sensitive photocurrent excited by terahertz (THz) radiation in dual-grating-gate (DGG) InAlAs/InGaAs/InAlAs/InP high electron mobility transistors (HEMT). For a circular polarization, the current measured between source and drain contacts changes its sign with the inversion of the radiation helicity. For elliptically polarizedradiation, the total current is described by superposition of the Stokes parameters with different weights. Moreover, by variation of gate voltages applied to individual gratings, the photocurrentcan be defined either by the Stokes parameter defining the radiation helicity or those for linearpolarization. We show that artificial non-centrosymmetric microperiodic structures with a two-dimensional electron system excited by THz radiation exhibit a dc photocurrent caused by the combined action of a spatially periodic in-plane potential and spatially modulated light. The results provide a proof of principle for the application of DGG HEMT for all-electric detection of the radiation's polarization state.