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Three-Dimensional Resolvable Plasmonic Concentric Compound Lens: Approaching the Axial Resolution from Microscale to Nanoscale
ACS Photonics ( IF 7 ) Pub Date : 2017-12-07 00:00:00 , DOI: 10.1021/acsphotonics.7b01003
Kai-Hao Chang , Yen-Chun Chen , Wen-Hao Chang , Po-Tsung Lee

We propose the design and working principle of a plasmonic concentric compound lens (CCL) comprising inner circular nanoslits and outer circular nanogrooves. Dual-wavelength operations have been achieved for 650 and 750 nm at nanoscale and microscale focal lengths along with their depth of focus (DOF). By tuning the arrangement of nanogrooves, the axial resolution can be modulated and the narrowest DOF is achieved by a design of gradually decreasing groove width. For the ultrahigh tunability of axial resolution, DOF over 400 nm for both working wavelengths is also achieved. We not only developed an approximate-perturbed-focus model for explaining the performance of DOF but also found an extraordinary way to improve the resolution. The enhanced resonance of central disk as nannoantenna in CCL also has great influence on nanofocusing with different deigns of outer nanogrooves. This work provides new sight of focusing ability governed by the general optical nanogrooves. The optimized CCL shows excellent focusing performance with a lateral resolution down to 0.32λ (λ = 650 nm), which is the best resolving ability achieved thus far in the near field region with a long focal length up to 500 nm.

中文翻译:

三维可分辨等离激元同心复合透镜:从微米级到纳米级的轴向分辨率接近。

我们提出了包括内圆纳米缝和外圆纳米沟槽的等离激元同心复合透镜(CCL)的设计和工作原理。已经在纳米级和微米级焦距及其焦点深度(DOF)上实现了650和750 nm的双波长操作。通过调整纳米凹槽的排列,可以调节轴向分辨率,并通过逐渐减小凹槽宽度的设计来实现最窄的自由度。对于轴向分辨率的超高可调性,两个工作波长的自由度也都超过了400 nm。我们不仅开发了一种近似摄动焦点模型来解释自由度的性能,而且还找到了一种提高分辨率的非凡方法。在CCL中,中心盘作为纳米天线的增强共振对纳米聚焦也有很大的影响,外部纳米沟槽的设计各不相同。这项工作提供了由一般光学纳米凹槽控制的聚焦能力的新视野。优化的CCL表现出出色的聚焦性能,横向分辨率低至0.32λ(λ= 650 nm),这是迄今为止在近场区域获得的最佳分辨能力,长焦距可达500 nm。
更新日期:2017-12-07
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