20 Mbit/s wireless communication demonstration using terahertz quantum devices

Scheme of the transmission setup based on a THz QCL and a THz QWP.

Terahertz communication (0.1~10 THz) has attracted much attention due to the high carrier frequency and large bandwidth over 100 Gbps. At present, most of the research work is focused on the frequency of 100 ~ 600 GHz, some has made good results by using the mature technology of component manufacturing and communication for microwave and millimeter-wave wireless communication. However, high speed communication system has not yet been realized in the carrier frequency between 1~10 THz. The communication demonstration system with carrier frequency between 1~10 THz relies largely on THz quantum cascade lasers (QCLs) and THz quantum-well photo-detectors (QWPs) as the emitter and receiver, respectively.

With a THz QCL and a frequency well-matched THz QWP set up for THz communication system, a data signal transmitted over a 2.2 m and data rate as high as 20Mbps was realized, and photocurrent extraction circuit was improved by Prof. Juncheng Cao's research group, from Key Laboratory of Terahertz Solid-State Technology, Chinese Academy of Sciences, based on their previous work. It is reported in Chinese Optics Letters, Vol. 13, No. 8, 2015 (Li Gu et al., 20 Mbps wireless communication demonstration using terahertz quantum devices).

The THz QWP matching the emitting frequency of the THz QCL can make sure that the QWP achieves more than 90% responsivity for the THz wave emitted from the QCL, which greatly improves the photocurrent outputting from the QWP. With the current extraction circuit enhanced according to THz QWP small signal model , the signal-to-noise ratio is improved while the bandwidth of the link increases to 11.8 MHz.

For the first time as far as we know, more than 20 Mbps wireless communication demonstration between 1~10 THz carrier frequency has been achieved. The results provide a feasible scheme for terahertz communication, and using THz QCLs and THz QWPs to build the THz high speed communication system has a great potential.

The following work will be focused on researching the high performance THz communication key devices, developing the high-speed THz modulation technology, improving the circuit bandwidth and realizing the THz high-speed communication systems.

COL封面故事：大气条件下在1~10THz频段成功实现20Mbps以上通信速率

图片说明：基于太赫兹QCL与QWP的通信演示系统示意图

太赫兹通信（0.1~10 THz）能够提供较高的载波频率以及较大的带宽来实现100 Gbps以上的传输速率，近些年成为研究热点。目前大部分的研究工作集中在100~600 GHz，研究人员借鉴微波与毫米波无线通信中成熟的器件制造技术与通信技术取得了一些较好的结果，但1 ~10 THz频段还未实现较高速率的通信系统。该频段的通信演示系统主要依赖THz量子级联激光器（QCLs）与THz量子阱探测器（QWPs）作为发射源与探测器。

中国科学院太赫兹固态技术重点实验室曹俊诚研究员课题组根据前期工作，采用频率相匹配的THz量子级联激光器（QCLs）与THz量子阱探测器（QWPs）建立THz通信系统，在距离2.2 m时通信速率达到了20 Mbps以上的实验结果。相关研究成果发表Chinese Optics Letters 2015年第8期上（Li Gu et al., 20 Mbps wireless communication demonstration using terahertz quantum devices）。

频率相匹配的QCL与QWP能保证太赫兹波有90%以上的吸收效率，极大地提高了探测器的光电流输出，根据太赫兹QWP器件小信号模型改进的光电流提取电路在提高信噪比的同时，将链路带宽提高至11.8MHz。

这是国际上首次报道大气条件下在 大于1THz频段成功实现20Mbps以上通信速率的实验。该研究结果为太赫兹通信提供了一种可行方案，采用THz QCL与 THz QWP作为发射源与探测器来搭建太赫兹高速通信系统具有很大潜力。

后续工作主要是研制高性能的太赫兹通信关键器件，开发高速太赫兹调制技术，提高电路带宽，实现太赫兹高速通信系统。