Wang Ride, Wu Qiang, Zhang Qi, Lu Yao, Zhao Wenjuan, Cai Wei, Qi Jiwei, Yao Jianghong, Xu Jingjun
Opt Express. 2018 Nov 26;26(24):31233-31243. doi: 10.1364/OE.26.031233.
Surface waves (SWs) have attracted a widespread attention due to the characteristic of subwavelength confinement and convenient manipulation in photonic integrated circuits. Though metasurface provides a powerful tool in realizing the conversion between freely propagating waves and surface modes in recent years, a gulf between guided waves (GWs) and SWs in terahertz (THz) range still exists as a bottleneck for on-chip photonic integrated devices. Here, we implemented the conversion from THz GWs to SWs through the coupling of a lithium niobate (LN) subwavelength waveguide and metasurface antennas on an all-feature on-chip THz integrated platform. The conversion process and transmission mode of the THz waves were directly visualized via a time-resolved imaging system. Based on the dynamic process, the formation of SWs could be clarified through analyzing the dispersion relation of propagating modes, which is in good agreement with numerical models. In further, relying on the numerical simulation, SWs were induced from the collective oscillations of the metasurface antenna array and the maximum coupling efficiency was around 62.6 percent. Our work provides an efficient approach to control of GWs, and promotes the practicability of THz surface integrated devices, including THz surface spectroscopy sensing.
表面波（SWs）因其在光子集成电路中具有亚波长限制和便于操控的特性而受到广泛关注。尽管超表面近年来为实现自由传播波与表面模式之间的转换提供了强大工具，但太赫兹（THz）频段的导波（GWs）与表面波之间仍存在差距，这是片上光子集成器件的一个瓶颈。在此，我们在全功能片上太赫兹集成平台上，通过铌酸锂（LN）亚波长波导与超表面天线的耦合，实现了太赫兹导波到表面波的转换。太赫兹波的转换过程和传输模式通过时间分辨成像系统直接可视化。基于该动态过程，通过分析传播模式的色散关系可以阐明表面波的形成，这与数值模型吻合良好。进一步地，依靠数值模拟，表面波由超表面天线阵列的集体振荡诱导产生，最大耦合效率约为62.6%。我们的工作为控制导波提供了一种有效方法，并推动了太赫兹表面集成器件（包括太赫兹表面光谱传感）的实用性。
