Zhao Tao, Gong Sen, Hu Min, Zhong Renbin, Liu Diwei, Chen Xiaoxing, Zhang Ping, Wang Xinran, Zhang Chao, Wu Peiheng, Liu Shenggang
Terahertz Research Center, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054, China.
Cooperative Innovation Centre of Terahertz Science, Chengdu, Sichuan, 610054, China.
Sci Rep. 2015 Nov 3;5:16059. doi: 10.1038/srep16059.
Terahertz (THz) radiation can revolutionize modern science and technology. To this date, it remains big challenges to develop intense, coherent and tunable THz radiation sources that can cover the whole THz frequency region either by means of only electronics (both vacuum electronics and semiconductor electronics) or of only photonics (lasers, for example, quantum cascade laser). Here we present a mechanism which can overcome these difficulties in THz radiation generation. Due to the natural periodicity of 2π of both the circular cylindrical graphene structure and cyclotron electron beam (CEB), the surface plasmon polaritions (SPPs) dispersion can cross the light line of dielectric, making transformation of SPPs into radiation immediately possible. The dual natural periodicity also brings significant excellences to the excitation and the transformation. The fundamental and hybrid SPPs modes can be excited and transformed into radiation. The excited SPPs propagate along the cyclotron trajectory together with the beam and gain energy from the beam continuously. The radiation density is enhanced over 300 times, up to 10(5) W/cm(2). The radiation frequency can be widely tuned by adjusting the beam energy or chemical potential. This mechanism opens a way for developing desired THz radiation sources to cover the whole THz frequency regime.
太赫兹（THz）辐射能够彻底改变现代科学与技术。时至今日，要开发出能够覆盖整个太赫兹频率范围的高强度、相干且可调谐的太赫兹辐射源，无论是仅借助电子学手段（包括真空电子学和半导体电子学）还是仅依靠光子学手段（例如激光、量子级联激光器），都仍然面临着巨大挑战。在此，我们提出一种能够克服太赫兹辐射产生过程中这些困难的机制。由于圆柱状石墨烯结构和回旋电子束（CEB）都具有自然的2π周期性，表面等离激元极化激元（SPPs）色散能够穿过电介质的光线，使得SPPs立即转化为辐射成为可能。这种双重自然周期性还给激发和转化带来了显著优势。基模和混合SPPs模能够被激发并转化为辐射。被激发的SPPs与电子束一同沿着回旋轨迹传播，并持续从电子束获取能量。辐射密度提高了300多倍，达到10(5) W/cm(2)。通过调节电子束能量或化学势，辐射频率能够得到广泛调谐。这一机制为开发出能够覆盖整个太赫兹频率范围的理想太赫兹辐射源开辟了一条道路。
