scholarly journals Enhanced Terahertz Amplification Based on Photo-Excited Graphene-Dielectric Hybrid Metasurface

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2448
Author(s):  
Shengnan Guan ◽  
Jierong Cheng ◽  
Tiehong Chen ◽  
Shengjiang Chang
Keyword(s):  
Transition Process ◽  
Pump Intensity ◽  
Gain Medium ◽  
Monolayer Graphene ◽  
Amplification Coefficient ◽  
Optical Pump ◽  
Dynamic Conductivity ◽  
Coupled Mode ◽  
Gain Loss ◽  
Terahertz Lasers

Graphene under optical pump has been shown to be an attractive gain medium with negative dynamic conductivity at terahertz frequencies. However, the amplification over a monolayer graphene is very weak due to its one-atom thickness. In this paper, the proposed graphene-dielectric reflective metasurface effectively improved terahertz field localization and enhanced coherent amplification. The amplification coefficient of 35 was obtained at 3.38 THz at room temperature with an infrared pump intensity of 8 W/mm2. As pump intensity increased from 0 to 15 W/mm2, we observed a loss–gain–loss transition process, which was discussed in detail through coupled-mode theory. In addition, amplification at different frequencies was achieved by merely re-optimizing the geometric parameters of the dielectric resonators. This study offers an effective solution for enhancing terahertz radiation and developing terahertz lasers.

Terahertz-wave generation using graphene

2012 ◽  
Vol 1437 ◽  
Author(s):  
Taiichi Otsuji ◽  
Stephane Boubanga Tombet ◽  
Akira Satou ◽  
Maxim Ryzhii ◽  
Victor Ryzhii
Keyword(s):  
Terahertz Wave ◽  
Wave Generation ◽  
Nonequilibrium Carrier ◽  
Terahertz Range ◽  
Two Dimensional ◽  
Carrier Relaxation ◽  
Dynamic Conductivity ◽  
Electrically Pumped ◽  
Terahertz Lasers ◽  
Recombination Dynamics

ABSTRACTIn this paper recent advances in terahertz-wave generation in graphene are reviewed. First, fundamental basis of the optoelectronic properties of graphene is introduced. Second, nonequilibrium carrier relaxation and recombination dynamics in optically or electrically pumped graphene is described to introduce a possibility of negative dynamic conductivity in a wide terahertz range. Third, recent theoretical advances toward the creation of current-injection graphene terahertz lasers are described. Fourth, unique terahertz dynamics of the two-dimensional plasmons in graphene are described. Finally, the advantages of graphene materials and devices for terahertz-wave generation are summarized.

Pressure-induced threshold optical pump intensity in a CdTe/ZnTe quantum dot

2016 ◽  
Vol 90 (3) ◽  
pp. 213-226 ◽  
Author(s):  
P. Sujanah ◽  
A. John Peter ◽  
Chang Woo Lee
Keyword(s):  
Quantum Dot ◽  
Pump Intensity ◽  
Optical Pump

scholarly journals Optical tunable multifunctional slow light device based on double monolayer graphene grating-like metamaterial

2021 ◽  
Author(s):  
Hui Xu ◽  
Xiaojing Wang ◽  
Zhiquan Chen ◽  
Xuelei Li ◽  
Longhui He ◽  
...  
Keyword(s):  
Slow Light ◽  
Incident Light ◽  
Monolayer Graphene ◽  
Group Index ◽  
Dark Mode ◽  
Coupled Mode ◽  
Frequency Selection ◽  
Electrostatic Doping ◽  
Tunable Device ◽  
Induced Transparency

Abstract A very simple optical tunable device, which can realize multiple functions of frequency selection, reflection and slow light, is presented at the investigation. The proposed device is constructed by a periodic grating-like structure. There are two dielectrics (graphene and silicon) in a period of the equivalent grating. The incident light will strongly resonate with the graphene of electrostatic doping, forming an evanescent wave propagating along the surface of graphene, and this phenomenon is the surface plasmon. Under constructive interference of the polaritons, a unique plasmonic induced transparency phenomenon will be achieved. The induced transparency produced by this device can be well theoretically fitted by the bright and dark mode of optical equivalent cavity which can be called coupled mode theory (CMT). This theory can well analyze the influence of various modes and various losses between the function of this device. The device can use gate voltages for electrostatic doping in order to change the graphene carrier concentration and tune the optical performance of the device. Moreover, the length of the device in y-direction is will be much larger than the length of single cycle, providing some basis for realizing the fast tunable function and laying a foundation for the integration. Through a simulation and calculation, we can find that the group index and group delay of this device are as high as 515 and 0.257 picoseconds (ps) respectively, so it can provide a good construction idea for the slow light device. The proposed grating-like metamaterial structure can provide certain simulation and theoretical help for the optical tunable reflectors, absorbers, and slow light devices.

scholarly journals Generalized coupled-mode formalism in reciprocal waveguides with gain, loss, anisotropy, or bianisotropy

2019 ◽  
Vol 99 (19) ◽  
Author(s):  
Weijin Chen ◽  
Zhongfei Xiong ◽  
Jing Xu ◽  
Yuntian Chen
Keyword(s):  
Coupled Mode ◽  
Gain Loss

Graphene Terahertz Lasers: Injection versus Optical Pumping

2013 ◽  
Vol 1505 ◽  
Author(s):  
Taiichi Otsuji ◽  
Akira Satou ◽  
Maxim Ryzhii ◽  
Vladimir Mitin ◽  
Victor Ryzhii
Keyword(s):  
Spectral Range ◽  
Population Inversion ◽  
Optical Pumping ◽  
Optically Pumped ◽  
Dynamic Conductivity ◽  
Graphene Layers ◽  
Nonequilibrium States ◽  
Injection Type ◽  
Terahertz Lasers ◽  
Graphene Structures

ABSTRACTIn this paper we demonstrate that graphene is one of the best materials for new types of terahertz lasers as optical and/or injection pumping of graphene can exhibit negative-dynamic conductivity in the terahertz spectral range. We analyze the formation of nonequilibrium states in optically pumped graphene layers and in forward-biased graphene structures with lateral p-i-n junctions and consider the conditions of population inversion and lasing. The latter provides a significant advantage of the injection pumping in realization of graphene terahertz lasers. We benchmark graphene as a prospective material for injection-type terahertz lasers.

Tunable terahertz photoconductivity of hydrogen functionalized graphene using optical pump-terahertz probe spectroscopy

Nanoscale ◽  
2018 ◽  
Vol 10 (29) ◽  
pp. 14321-14330 ◽  
Author(s):  
Srabani Kar ◽  
Dipti R. Mohapatra ◽  
A. K. Sood
Keyword(s):  
Spectral Dependence ◽  
Monolayer Graphene ◽  
Functionalized Graphene ◽  
Optical Pump ◽  
Quantitative Understanding ◽  
Probe Spectroscopy ◽  
Different Levels

We show that the terahertz photoconductivity of monolayer graphene following 800 nm femtosecond optical pump excitation can be tuned by different levels of hydrogenation (graphane) and provide a quantitative understanding of the unique spectral dependence of photoconductivity.

Tunable dual plasmon-induced transparency and slow-light analysis based on monolayer patterned graphene metamaterial

2022 ◽  
Author(s):  
Pengju Yao ◽  
Biao Zeng ◽  
Enduo Gao ◽  
Hao Zhang ◽  
Chao Liu ◽  
...  
Keyword(s):  
Absorption Rate ◽  
Slow Light ◽  
Monolayer Graphene ◽  
Destructive Interference ◽  
Group Index ◽  
Coupled Mode ◽  
External Bias ◽  
Internal Mechanism ◽  
Induced Transparency ◽  
Plasmon Induced Transparency

Abstract We propose a novel terahertz metamaterial structure based on patterned monolayer graphene. This structure produces an evident dual plasmon-induced transparency (PIT) phenomenon due to destructive interference between bright and dark modes. Since the Fermi level of graphene can be adjusted by an external bias voltage, the PIT phenomenon can be tuned by adjusting the voltage. Then the coupled-mode theory (CMT) is introduced to explore the internal mechanism of the PIT. After that, we investigate the variation of absorption rate at different graphene carrier mobilities, and it shows that the absorption rate of this structure can reach 50%, which is a guideline for the realization of graphene terahertz absorption devices. In addition, through the study of the slow-light performance for this structure, it is found that its group index is as high as 928, which provides a specific theoretical basis for the study of graphene slow-light devices.

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