Abstract-Current-injection terahertz lasing in a distributed-feedback dual-gate graphene-channel transistor

G. Tamamushi,  T. Watanabe,  J. Mitsushio,  A. A. Dubinov,  A. Satou, T. Suemitsu,  M. Ryzhii,  V. Ryzhii,  T. Otsuji

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10111/1011126/Current-injection-terahertz-lasing-in-a-distributed-feedback-dual-gate/10.1117/12.2249983.pdf?SSO=1

This paper reviews recent advancement on the research toward graphene-based terahertz (THz) lasers. Optical and/or injection pumping of graphene can enable negative-dynamic conductivity in the THz spectral range, which may lead to new types of THz lasers. A forward-biased graphene structure with a lateral p-i-n junction was implemented in a distributed-feedback (DFB) dual-gate graphene-channel FET and observed a single mode emission at 5.2 THz at 100K. The observed spectral linewidth fairly agrees with the modal gain analysis based on DFB-Fabry-Perrot hybrid-cavitymode modeling. Although the results obtained are still preliminary level, the observed emission could be interpreted as THz lasing in population-inverted graphene by carrier-injection.

© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

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.

Abstract: Ultrafast carrier dynamics and terahertz emission in optically pumped graphene at room temperature

http://prb.aps.org/abstract/PRB/v85/i3/e035443

Received 5 April 2011; revised 11 November 2011; published 26 January 2012

We report, within a picosecond time scale, fast relaxation and relatively slow recombination dynamics of photogenerated electrons and holes in an exfoliated graphene under infrared pulse excitation. We conduct time-domain spectroscopic studies using an optical pump and terahertz probe with an optical probe technique and show that graphene sheet amplifies an incoming terahertz field. The graphene emission spectral dependency on laser pumping intensity shows a threshold-like behavior, testifying to the occurrence of the negative conductivity and the population inversion. The phase behavior of the measured terahertz electric field also shows clear Lorentzian-like normal dispersion around the gain peak, testifying to the amplification that can be attributed to stimulated emission of photocarriers in the inverted states. The emission spectra clearly narrow at a longer terahertz probe delay time, giving evidence that the quasi-Fermi energy moves closer to the equilibrium at this longer terahertz probe delay time.

©2012 American Physical Society

URL:

http://link.aps.org/doi/10.1103/PhysRevB.85.035443

DOI:

10.1103/PhysRevB.85.035443

PACS:

78.45.+h, 78.47.D-, 78.66.Tr, 78.70.-g

^*stephanealbon@hotmail.com