Abstract-Enhanced plasmonic nanofocusing of terahertz waves in tapered graphene multilayers

Weiwei Liu, Bing Wang, Shaolin Ke, Chengzhi Qin, Hua Long, Kai Wang, and Peixiang Lu
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-13-14765

We investigate the plasmonic nanofocusing of terahertz waves in tapered graphene multilayers separated by dielectrics. The nanofocusing effect is significantly enhanced in the graphene multilayer taper compared with that in a single layer graphene taper due to interlayer coupling between surface plasmon polaritons. The results are optimized by choosing an appropriate layer number of graphene and the field amplitude has been enhanced by 620 folds at λ = 50 μm. Additionally, the structure can slow light to a group velocity ~1/2815 of the light speed in vacuum. Our study provides a unique approach to compress terahertz waves into deep subwavelength scale and may find great applications in terahertz nanodevices for imaging, detecting and spectroscopy.

© 2016 Optical Society of America

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Abstract-Branchlike nano-electrodes for enhanced terahertz emission in photomixers

Qing Yang Steve Wu1, Hendrix Tanoto1, Lu Ding1, Chan Choy Chum1, Bing Wang2, Ah Bian Chew1, Agnieszka Banas3, Krzysztof Banas3, Soo Jin Chua4,5 and Jinghua Teng1,5

http://iopscience.iop.org/0957-4484/26/25/255201

elecsj@nus.edu.sg jh-teng@imre.a-star.edu.sg

1 Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore 117602, Singapore
2 School of Physics, Huazhong University of Science and Technology, Wuhan, People's Republic of China
3 Singapore Synchrotron Light Source, National University of Singapore, Singapore 117576, Singapore
4 Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
5 Authors to whom any correspondence should be addressed. 

Branchlike nano-electrode structures were found to improve the THz emission intensity of a photomixer by approximately one order of magnitude higher than that of a photomixer with one row of nano-electrodes separated by the same 100 nm gap. The enhancement is attributed to a more efficient collection of generated carriers, which is in turn due to a more intense electric field under the branchlike nano-electrodes' structures. This is coupled with an increased number of effective areas where strong tip-to-tip THz field enhancements were observed. The optical-to-THz conversion efficiency of the photomixers with the new branchlike nano-electrodes was found to be 10 times higher. The more efficient THz photomixer will greatly benefit the development of continuous-wave THz imaging and spectroscopy systems.