超快激光成丝产生太赫兹波的传输特性研究

Femtosecond laser filamentation is a unique nonlinear optical phenomenon being able to generate THz wave at a remote distance up to hundreds of meters. Laser-induced filaments can guide energy in the form of electric current and microwave or infrared laser radiation in air. Related works regarding the plasma filaments guiding the terahertz wave have not yet been reported abroad. This innovation research is to study the fundamental properties of THz wave propagation during ultrafast laser filamentation, providing a theoretical basis on applications such as THz remote sensing, spectroscopy detection in air and environmental monitoring, etc. Study mainly includes near-field spatial mode, the propagation mechanism and parameters optimization of THz wave propagation during ultrafast laser filamenation. The key scientific issues in the research need to be solved including experimental near-field measurement technique on the THz wave spatial mode, the physical model for THz wave propagation and the optimization of parameters. We expect to obtain the THz spatial distribution and establish the physical model and to form a theory system on THz wave propagation during the ultrafast laser filametation and to provide a theoretical basis for realization of the THz remote sensing.

超快激光成丝可远程辐射太赫兹波，可以引导微波与红外激光能量的传输。光丝能否作为太赫兹波波导，迄今尚需研究。本项目开展基于超快激光成丝辐射太赫兹波在光丝（等离子体通道）中传输特性的创新研究，为实现太赫兹波远程遥感、光谱探测与环境检测等应用提供研究基础，研究内容主要包括：实验研究太赫兹波在光丝中传输的近场空间分布模式、太赫兹波在光丝中传输的物理机制与太赫兹波在光丝中传输特性影响参数的优化。项目研究要解决的关键科学问题有：太赫兹波在光丝中传输的近场测量技术、太赫兹波在光丝中传输的物理模型的建立与传输参数的优化技术。课题预期的成果是实验测量得到太赫兹波在光丝中传输的近场空间模式，建立太赫兹波传输的物理模型，初步建立太赫兹波在光丝中传输特性理论，为实现太赫兹波远程遥感提供理论基础。

本项目拟研究超快激光成丝产生太赫兹波在空气中的传输特性，在本项目的资助下，研究了影响太赫兹波在等离子体中传输的因素，发现等离子体密度与半径、太赫兹频率会影响太赫兹波在光丝中的传输；研究结果显示：(1)太赫兹波被束缚于光丝中传输，束缚作用将随太赫兹波频率的增大而减弱；(2)高等离子体密度具有更强的空间束缚能力；(3)超快激光电离空气产生的等离子体通道的半径越大，太赫兹波束缚半径也随之变大。基于对太赫兹波在等离子体通道(光丝)中的研究，提出简化的一维负介电常数光传输波导模型，太赫兹波在等离子体中折射率的变化是赫兹波传输的主要影响因素，揭示了太赫兹波在等离子体中传输的物理机制。