[论文解读] Individual nanoantennas empowered by bound states in the continuum for nonlinear photonics

Kirill Koshelev, Sergey Kruk+5 more|arXiv (Cornell University)|Aug 26, 2019

Photonic and Optical Devices参考文献 31被引用 175

一句话总结

本文通过实验证明了一个孤立的亚波长 AlGaAs 纳米谐振腔，承载准BIC共振，使用结构光激发，并作为非线性纳米天线实现了创纪录的高二次谐波生成效率。

ABSTRACT

Bound states in the continuum (BICs) represent localized modes with energies embedded in the continuous spectrum of radiating waves. BICs were discovered initially as a mathematical curiosity in quantum mechanics, and more recently were employed in photonics. Pure mathematical bound states have infinitely-large quality factors (Q factors) and zero resonant linewidth. In optics, BICs are physically limited by a finite size, material absorption, structural disorder, and surface scattering, and they manifest themselves as the resonant states with large Q factors, also known as supercavity modes or quasi-BICs. Optical BIC resonances have been demonstrated only in extended 2D and 1D systems and have been employed for distinct applications including lasing and sensing. Optical quasi-BIC modes in individual nanoresonators have been discovered recently but they were never observed in experiment. Here, we demonstrate experimentally an isolated subwavelength nanoresonator hosting a quasi-BIC resonance. We fabricate the resonator from AlGaAs material on an engineered substrate, and couple to the quasi-BIC mode using structured light. We employ the resonator as a nonlinear nanoantenna and demonstrate record-high efficiency of second-harmonic generation. Our study brings a novel platform to resonant subwavelength photonics.

研究动机与目标

• 在孤立的纳米谐振腔中推动并实现连续体边界态(BIC)；用于非线性光子学。
• 在亚波长纳米谐振腔中实验性演示准BIC模的激发。
• 展示该纳米天线作为具有高二次谐波生成效率的非线性元件。

提出的方法

• 在定制基底上制造亚波长 AlGaAs 纳米谐振腔。
• 利用结构光辨识并调谐以耦合到准BIC模。
• 表征共振品质因子和非线性响应。
• 展示纳米天线的二次谐波生成。
• 将性能与常规谐振腔进行比较，以突出准BIC的优势。

实验结果

研究问题

• RQ1 孤立的亚波长纳米谐振腔是否能承载可被高效激发的准BIC共振？
• RQ2 与准BIC模耦合是否能在单一纳米天线中实现增强的非线性光学过程？
• RQ3 在结构光驱动下，这样的纳米天线可达到的二次谐波生成效率是多少？

主要发现

• 通过实验证明了一个孤立的亚波长纳米谐振腔承载准BIC共振。
• 该谐振腔通过在定制基底上的 AlGaAs 制作，并通过结构光激发。
• 该纳米天线作为具有创纪录高二次谐波生成效率的非线性元件。
• 单个纳米谐振腔中的准BIC模在紧凑平台上实现了高-Q共振。