arXiv 2407.196202024-07-29physics.optics

与 $λ/5000$ 纳米波导的方向性耦合

Directional coupling to a $λ/5000$ nano-waveguide

Alessandro Tuniz, Sabrina Garattoni, Han-Hao Cheng, Giuseppe Della Valle

AI总结：

本文提出并实验验证了一种将太赫兹辐射高效耦合至λ/5000纳米间隙波导的策略，通过相位匹配介电与纳米间隙模式实现约10%耦合效率，为片上纳米光谱和量子技术提供新途径。

摘要：

硅基微器件被认为是将几种太赫兹技术整合到一个通用且实用的平台上的有希望的候选者。其实用性源于相对较低的损耗、器件紧凑性、易于制造以及广泛的可用无源和有源功能。然而，典型器件的占用面积受衍射限制在几百微米，这阻碍了太赫兹频率的新兴纳米级应用。虽然金属间隙模式提供了纳米级太赫兹限制，但高效耦合到它们是困难的。在这里，我们提出并实验演示了一种策略，用于将太赫兹辐射（λ=1 mm）高效接口到由金膜中刻蚀的纳米间隙形成的波导，该纳米间隙宽 200 nm（λ/5000），长达 4.5 mm。设计原理依赖于相位匹配介电波导和纳米间隙波导模式，当并排放置时，它们之间会产生高效的方向性耦合。通过介电波导的宽带远场太赫兹传输实验揭示了在设计波长附近由于谐振耦合而产生的传输凹陷。金层表面的近场测量证实，这种凹陷伴随着功率向纳米间隙的转移，估计耦合效率约为 10%。我们的方法为高效接口毫米波和近红外光子电路提供了一条途径，提供了可控和定制的纳米级太赫兹限制，对片上纳米光谱学、电信和量子技术具有重要意义。

英文摘要：

Silicon-based micro-devices are considered promising candidates for consolidating several terahertz technologies into a common and practical platform. The practicality stems from the relatively low loss, device compactness, ease of fabrication, and wide range of available passive and active functionalities. Nevertheless, typical device footprints are limited by diffraction to several hundreds of micrometers, which hinders emerging nanoscale applications of terahertz frequencies. While metallic gap modes provide nanoscale terahertz confinement, efficiently coupling to them is difficult. Here we present and experimentally demonstrate a strategy for efficiently interfacing sub-terahertz radiation (λ=1 mm) to a waveguide formed by a nanogap, etched in a gold film, that is 200 nm (λ/5000) wide and up to 4.5 mm long. The design principle relies on phase matching dielectric and nanogap waveguide modes, resulting in efficient directional coupling between them when placed side-by-side. Broadband far field terahertz transmission experiments through the dielectric waveguide reveal a transmission dip near the designed wavelength due to resonant coupling. Near field measurements on the surface of the gold layer confirm that such a dip is accompanied by a transfer of power to the nanogap, with an estimated coupling efficiency of ~10%. Our approach provides a pathway for efficiently interfacing millimeter-wave and near-infrared photonic circuits, providing controlled and tailored nanoscale terahertz confinement, with important implications for on-chip nanospectroscopy, telecommunications, and quantum technologies.

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