Hiroaki Niwa, Naotaka Yoshikawa, Masashi Kawaguchi, Masamitsu Hayashi, and Ryo Shimanohttps://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-9-13331&id=450178
Hiroaki Niwa, Naotaka Yoshikawa, Masashi Kawaguchi, Masamitsu Hayashi, and Ryo Shimano
|(a) THz generation from a spintronic THz emitter. Transient spin current |
|The gated graphene sample device in which the graphene film acts as a channel between source and drain electrodes subjected to a constant potential difference of 0.2 mV. Image from Science Advances|
In a new study, a team of researchers demonstrates that graphene's nonlinearity can be very efficiently controlled by applying comparatively modest electrical voltages to the material.
Wei-Mang Pan and Jiu-Sheng Li
|(a) Three-dimensional schematic diagram of terahertz metasurface with diversified functions, (b) Designed unit cell with the relevant geometric parameters|
Xiangfei Gao, Zebin Zhu, Jing Yuan, and Liyong Jiang
| Real part (a) and imaginary part (b) of the photonic bands of the graphene-Si 1D APC when |
Graphene is conceivably the most nonlinear optoelectronic material we know. Its nonlinear optical coefficients in the terahertz frequency range surpass those of other materials by many orders of magnitude. Here, we show that the terahertz nonlinearity of graphene, both for ultrashort single-cycle and quasi-monochromatic multicycle input terahertz signals, can be efficiently controlled using electrical gating, with gating voltages as low as a few volts. For example, optimal electrical gating enhances the power conversion efficiency in terahertz third-harmonic generation in graphene by about two orders of magnitude. Our experimental results are in quantitative agreement with a physical model of the graphene nonlinearity, describing the time-dependent thermodynamic balance maintained within the electronic population of graphene during interaction with ultrafast electric fields. Our results can serve as a basis for straightforward and accurate design of devices and applications for efficient electronic signal processing in graphene at ultrahigh frequencies.