Modes in silver-iodide-lined hollow metallic waveguides mapped by terahertz near-field time-domain microscopy
Modes in silver-iodide-lined hollow metallic waveguides mapped by terahertz near-field time-domain microscopy
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DOI：
10.1364/josab.30.000127
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发表时间：
2013
影响因子：
1.9
通讯作者：
M. Navarro‐Cía;C. Bledt;M. Vitiello;H. Beere;D. Ritchie;J. Harrington;O. Mitrofanov
中科院分区：
文献类型：
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作者：
M. Navarro‐Cía;C. Bledt;M. Vitiello;H. Beere;D. Ritchie;J. Harrington;O. Mitrofanov
当主波导模转变为混合HE11模时，中空金属波导中的薄介质层被用来改善波导的传输特性。研究了1μm厚的碘化银(AgI)薄膜在太赫兹(�)频率下对柱形波导中基模的影响，在介质层厚度小于最佳厚度的情况下，最低阶模的分布在1-3.2太赫兹范围内与�≈11和μ11模相似，这是由时间分辨近场测量确定的，并得到了数值验证。由于多模传播，高次模被实验检测为模混合。应用数值电磁建模来解决模式结构的模糊性，使我们能够将实验检测到的模式与TM11和高阶模式TE12的叠加关联起来。所测得的模式分布表明，在超薄介质区(h≪0.1Ef)，介质层不会将主模转变为低损耗的λ模。然而，由于模式跳动，可以形成类似于HE11和TE01模式的实验模式图案。结果表明，Ag/AgI光波导可用于THz波在TE01模或TE12模中的传输，且对其他模具有较高的分辨率。2012年美国光学学会OCIS代码：110.6795、180.4243、320.7100。
Thin dielectric layers inside hollow metallic waveguides are used to improve the waveguide transmission characteristics as the dominant waveguide mode changes into the hybrid HE11 mode. We investigate the effect of 1 μm thick silver iodide (AgI) coatings on the fundamental modes in cylindrical waveguides at terahertz (THz) frequencies, in the regime of the dielectric layer being thinner than the optimal thickness hopt� 2 THz� ≈ 20 μm. In the region of 1–3.2 THz, the lowest-order modes are similar in profile to the TE11 and TM11 modes, as determined by the timeresolved near-field measurements and verified numerically. Higher-order modes are detected experimentally as mode mixtures due to the multimode propagation. Numerical electromagnetic modeling is applied to resolve the mode structure ambiguity, allowing us to correlate experimentally detected patterns with a superposition of the TM11 and the higher-order mode, TE12. Mode profiles determined here indicate that in the regime of ultrathin dielectric (h ≪ 0.1λeff), the dielectric layer does not transform the dominant mode into the low-loss HE11 mode. Experimental mode patterns similar to the HE11 and the TE01 modes nevertheless can be formed due to mode beating. The results indicate that the Ag/AgI waveguides can be used for guiding THz waves in the TE01 mode or the TE12 mode with high discrimination against other modes. © 2012 Optical Society of America OCIS codes: 110.6795, 180.4243, 320.7100.