太赫兹片上系统和基于微纳结构的太赫兹超宽谱源的研究进展

Research progress of super-continuum terahertz source based on nano-structures and terahertz lab on-chip system

目前太赫兹辐射信号的功率不高,辐射带宽也较窄,这些对于生物化学、含能材料的太赫兹检测应用领域来说是一大限制因素,因此如何获得宽谱高功率的太赫兹源对于太赫兹时域光谱系统的发展是非常重要的;另一方面,常规的太赫兹系统是在自由空间传输探测的,测量过程需要在氮气或者干燥空气环境中进行,以克服空气中水的吸收干扰,同时自由空间中的光场与物质相互作用的模式又降低了物质检测的灵敏度,这对于痕量物质检测来说构成了挑战.面对这一问题,太赫兹片上系统利用微纳结构中的局域场效应实现对物质的低浓度检测,此方案有助于解决这一应用难题.综上所述,本文分成以下两部分阐述:首先阐述了纳米金属薄膜作为新的太赫兹源,它可以同时产生非相干的和相干的太赫兹信号,其输出为超过100 THz的太赫兹-红外辐射,功率高达10 mW,这种超宽谱和高功率现象主要是由于非相干的热辐射效应引起的;第二,阐述了基于不同传输线结构、不同基底材料的太赫兹片上系统结构设计和光谱应用.基于共面带状线结构和聚合物材料基底的太赫兹片上系统有着较低的损耗,能够实现超过2 THz带宽的测量和生物化学应用.

The terahertz applications of bio-materials and energetic materials are hindered by the low power-intensity of the terahertz output and the narrow band of terahertz emission. So the crucial part of the development of terahertz time- domain spectroscopy （TDS） systems is the new terahertz source with broadband frequency range and high power output. As to the free-space TDS system, the system is necessarily purged by dried nitrogen gas to remove the absorbed water vapor. In addition, the low detection sensitivity also exists because of the free-space interactions between the terahertz emission and the substances. To address these problems, terahertz lab on-chip system is proposed. The local field effect in the nano-structures of on-chip system can contribute to the detection of low concentration of the substance. The present paper is composed of two sections. Firstly, a new terahertz source based on the metal nano-film can produce an intense and broad-band terahertz-infrared emission, which is comprised of incoherent terahertz-infrared signals and coherent terahertz signals. This emission can cover more than 100 THz and has an output power of up to 10 mW. This optical phenomenon mainly arises from the incoherent thermal radiation effect. Secondly, the terahertz lab on-chip systems with different transmission lines and different substrates are clarified. There exists lower loss on the on-chip system with coplanar stripline structure and copolymer substrate. High sensitivity of biological detection in terahertz band of up to 2 THz can be achieved by using this system.