Since the British physicists Andrei Heim and Konstantin Novoselov successfully separated graphene from graphite in 2004, this magical material has attracted the interest of many scientists around the world. Paying more attention to its mechanical toughness, superior electrical and thermal conductivity, which combines only one atom thick and honeycomb material. According to a recent report by the physicist organization network, a team of scientists at Iowa State University in the United States has discovered two new properties of graphene: electronic particle inversion and wide-band optical gain, which can be applied to high-speed telecommunication equipment and laser technology. on. Because the power of graphene is so "magic", an international team of scientists is planning to make graphene artificially, making it perform better and more perfect. Excited electron broadband particle inversion . Assistant Professor of the Department of Physics and Astronomy at Iowa State University, and Associate Research Fellow of the US Department of Energy's Ames Laboratory, Wang Jigang, led a research team that flashed very short laser pulses in graphene. A new graphene state of light-excited electron broadband particle number inversion is immediately discovered. Under normal conditions, most of the electrons occupy a low-energy state, and only a few will fill a high-energy state. In the reverse of the number of particles, the opposite is true: more electrons fill the high energy state rather than the low energy. In nature, this number of particles is very rare and can have very unusual properties. Thus, in graphene, the new state produces a visible infrared light gain. Simply put, light gain means that more visible light "outs" than "in", which can only occur when using a gain medium as an external pump and then stimulating with stimulated light. The researchers' findings can open the door to high-efficiency amplifiers and extremely fast optoelectronic devices in the telecommunications industry. Wang Jingang said: "This is very exciting. Graphene is possible as an optical amplifying gain medium. It can be used in high-speed modulators for broadband optical amplifiers or telecommunications, and even affects the development of graphene-based lasers." The research results were recently published in the journal Physical Review Letters. Creating a nonlinear state of dynamism Wang Jigang believes that other scientists have studied the optical properties of graphene, but mainly linear. His research team can serve as a bridge to help raise awareness of the new properties of graphene to compensate for the gaps in understanding of current research, and to understand the unbalanced electronic states by interpreting the nonlinear optical properties of graphene. The research team's conclusions may cause graphene to form a new "particularly unconventional state" that leads to population inversion and optical gain. He explained: "Linear optical properties can only transmit light, an optical signal enters and exits the material. But non-linear properties can change and adjust the signal, not just the transmission, to provide functionality for new device applications. "In this respect, this is the first time that a new breakthrough has been made. It is observed that graphene is in a state of extremely dense electron composition, that is, a highly nonlinear state. Graphene therefore has unique properties." The research team adopted The high-quality graphite monolayer produced by Ames Laboratories uses an ultrafast laser with only 35 femtosecond short pulsed light to "excite" the material's electrons. It has been found that by measuring the light-induced electronic state, when the pulse energy pump is increased above the threshold, the photoconductivity or absorption of the graphene layer changes from positive to negative, resulting in optical gain. The results show that in the state of particle reversal, graphene is excited by light and emits much more light than it absorbs, and the absorption is negative. The researchers explained that this means that the population inversion is indeed based on exciting graphene and more light coming out of the inversion medium than on the incoming light, thereby achieving optical gain. The optical gain layer it emits is only one atom thick, and this effect requires hundreds of times the thickness of a conventional semiconductor optical amplifier.
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