Abstract- Metal-graphene hybridized plasmon induced transparency in the terahertz frequencies

Anqi Yu, Xuguang Guo, Yiming Zhu, Alexey V. Balakin, Alexander P. Shkurinov,

(a) The proposed split T-shape metal/dielectric/graphene structure. (b) The top view of the proposed structure.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-24-34731

In this work, metal-graphene hybridized plasmon induced transparency (PIT) is systematically studied in the proposed simple metal/dielectric/graphene system. The PIT effect is the result of the coupling between the bright dipolar modes excited in the graphene regions under the shorter metallic bars and the dark quadrupolar modes excited in the graphene regions under the longer metallic bars. The coupled Lorentz oscillator model is used to help explain the physical origin of the PIT effect. Other than being tuned by the distance and the lateral displacement of the orthogonal metallic bars, the coupling efficiency can be further enhanced by the in-phase coupling or quenched by the out-of-phase coupling between the adjacent unit cells. Reduced barrier thickness will result in the enhancement of the coupling strengths and the scaling down of the device. Finally, we show that the PIT window can be actively tuned by changing the Fermi energy of graphene. The proposed structure has potential applications in actively tunable THz modulators, sensors and filters.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Plasmon ratchet effect with electrons and holes simultaneously existing in the graphene channel: a promising effect for the terahertz detection

Anqi Yu

http://iopscience.iop.org/article/10.1088/1361-6463/aad942

In this work, the plasmon drag effect in the grating gated graphene with symmetric unit cell, the plasmon ratchet effect and the photo-thermoelectric effect in the grating gated graphene with asymmetric unit cell are studied. The correlation between the total responsivity of the plasmon drag effect and the source-drain bias is calculated numerically through the hydrodynamic approach under small source-drain bias approximation. The total responsivity of the plasmon drag effect under small source-drain bias is found to be much smaller than the responsivity of the unidirectional travelling plasmons. The responsivity of the plasmon ratchet effect is calculated by fixing the lengths of the longer gated region and ungated region and changing the lengths of the shorter gated region and ungated region. The results show that non-zero plasmon ratchet responsivity can be obtained by only assuming one kind of charge carrier in the whole channel. By assuming holes in the shorter gated region and electrons in the other regions, the maximum responsivity is much higher than the former and can be as high as that reported in the reference. The responsivity of the photo-thermoelectric effect can be higher than that of the plasmon ratchet effect for currently available graphene. For ideal graphene with ultrahigh mobility, however, the responsivity of the photo-thermoelectric effect is orders of magnitude smaller than that of the plasmon ratchet effect.

Abstract-Toward Sensitive Room-Temperature Broadband Detection from Infrared to Terahertz with Antenna-Integrated Black Phosphorus Photoconductor

http://onlinelibrary.wiley.com/doi/10.1002/adfm.201604414/abstract;jsessionid=6D6EEA515BD415551858CA0C703C0EFC.f01t01?systemMessage=Wiley+Online+Library+Journal+subscribe+and+renew+pages+for+some+journals+will+be+unavailable+on+Wednesday+11th+January+2017+from+06%3A00-12%3A00+GMT+%2F+01%3A00-07%3A00+EST+%2F+14%3A00-20%3A00+SGT+for+essential+maintenance.+Apologies+for+the+inconvenience

Graphene-like two-dimensional materials (graphene, transition-metal dichalcogenides (TMDCs)) have received extraordinary attention owing to their rich physics and potential applications in building nanoelectronic and nanophotonic devices. Recent works have concentrated on increasing the responsivity and extending the operation range to longer wavelengths. However, the weak absorption of gapless graphene, and the large bandgap (>1 eV) and low mobility in TMDCs have limited their spectral usage to only a narrow range in the visible spectrum. In this work, we demonstrate for the first time a high-performance, antenna-integrated, black phosphorus (BP)-based photoconductor with ultra-broadband detection from the infrared to terahertz frequencies. The good trade-off between the moderate bandgap and good mobility results in a broad spectral absorption that is superior to that of graphene. Different photoconductive mechanisms, such as photothermoelectric (PTE), bolometric, and electron–hole generation can be distinguished depending on the device geometry, incident wavelength, and power. Especially, the photoconductive response remains highly efficient, even when the photon energy is extended to the terahertz (THz) band at room temperature, which is driven by the thermoelectric-induced well. The proposed photodetectors have a superior performance with an excellent sensitivity of over 300 V W−1, low noise equivalent power (NEP) (smaller than 1 nW Hz−0.5(10 pW Hz−0.5) with respect to the incident (absorbed) power), and fast response, all of which play key roles in multispectral biological imaging, remote sensing, and optical communications.

Abstract-Highly Sensitive and Wide-Band Tunable Terahertz Response of Plasma Waves Based on Graphene Field Effect Transistors

• Lin Wang,
• Xiaoshuang Chen,
• Anqi Yu,
• Yang Zhang,
• Jiayi Ding
• & Wei Lu

• Affiliations
• Contributions
• Corresponding author

http://www.nature.com/srep/2014/140627/srep05470/full/srep05470.html

Scientific Reports

 

4,

 

Article number:

 

5470

 

doi:10.1038/srep05470

Received

 

30 January 2014 

Accepted

 

27 May 2014 

Published

 

27 June 2014

Terahertz (THz) technology is becoming a spotlight of scientific interest due to its promising myriad applications including imaging, spectroscopy, industry control and communication. However, one of the major bottlenecks for advancing this field is due to lack of well-developed solid-state sources and detectors operating at THz gap which serves to mark the boundary between electronics and photonics. Here, we demonstrate exceptionally wide tunable terahertz plasma-wave excitation can be realized in the channel of micrometer-level graphene field effect transistors (FET). Owing to the intrinsic high propagation velocity of plasma waves (>~10⁸ cm/s) and Dirac band structure, the plasma-wave graphene-FETs yield promising prospects for fast sensing, THz detection, etc. The results indicate that the multiple guide-wave resonances in the graphene sheets can lead to the deep sub-wavelength confinement of terahertz wave and with Q-factor orders of magnitude higher than that of conventional 2DEG system at room temperature. Rooted in this understanding, the performance trade-off among signal attenuation, broadband operation, on-chip integrability can be avoided in future THz smart photonic network system by merging photonics and electronics. The unique properties presented can open up the exciting routes to compact solid state tunable THz detectors, filters, and wide band subwavelength imaging based on the graphene-FETs.