Katyba G M, Chizhov P A, Kurlov V N, Dolganova I N, Garnov S V, Zaytsev K I, Bukin V V
Opt Express. 2022 Jan 31;30(3):4215-4230. doi: 10.1364/OE.447060.
In this paper, hollow-core antiresonance sapphire waveguides were applied to guide the THz radiation emitted by the two-color laser air plasma, as well as to manage the THz source angular distribution. For this aim, three distinct waveguides were developed. Each of them is based on a cylindrical sapphire tube, either suspended in free space or coated by a polymer. The waveguides were first studied numerically, using the finite-difference eigenmode method, and experimentally, using the in-house THz pulsed spectrometer. The observed data uncovered the antiresonance regime of their operation, as well as their ability to guide broadband THz pulses over tens of centimeters with a high optical performance. The waveguides were then used to couple and guide (over the considerable distance) of THz radiation from the in-house two-color laser air plasma emitter, that exploits the mJ-energy-level femtosecond pulses of a Ti-sapphire laser. Small dispersion of a THz pulse and low-to-moderate propagation loss in the developed waveguide were observed, along with a considerable narrowing of the THz radiation angular distribution after passing the waveguide. Our findings revealed that such technologically-reliable hollow-core sapphire waveguides can boost the performance of laser air plasma-based THz emitters and make them more suitable for applications in the vigorously-explored THz sensing and exposure technologies.
在本文中，空心反谐振蓝宝石波导被用于引导双色激光空气等离子体发出的太赫兹辐射，并控制太赫兹源的角分布。为此，开发了三种不同的波导。它们每一种都基于圆柱形蓝宝石管，要么悬浮在自由空间中，要么涂覆有聚合物。首先使用有限差分本征模方法对波导进行了数值研究，并使用内部太赫兹脉冲光谱仪进行了实验研究。观测数据揭示了它们的反谐振工作模式，以及它们在数十厘米的距离上以高光性能引导宽带太赫兹脉冲的能力。然后，这些波导被用于耦合和引导（在相当长的距离上）来自内部双色激光空气等离子体发射器的太赫兹辐射，该发射器利用了钛宝石激光器的毫焦耳能量级飞秒脉冲。观测到太赫兹脉冲的色散较小，并且在开发的波导中传播损耗较低到中等，同时太赫兹辐射通过波导后的角分布显著变窄。我们的研究结果表明，这种技术可靠的空心蓝宝石波导可以提高基于激光空气等离子体的太赫兹发射器的性能，并使其更适合在蓬勃发展的太赫兹传感和辐照技术中的应用。
