集成共振單位元件組成之寬頻刻作超穎表面

Broadband metasurface with integrated resonant units

陳郁涵(Yu-Han Chen)

指導教授 ： 蔡定平

國立臺灣大學/理學院/物理學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201801686

摘要

由多個共振器或一個具有多個共振模態的共振器組成的單位構建模塊，我們稱之為集成共振單位元(簡稱IRU)，其顯示具有實現平滑和線性相位色散關係的能力，以及在連續性和極寬頻得頻譜上具有調變高振幅的能力。利用集成共振單位元的特性，我們展示了三種消色差超穎梯度板，光束偏折的反射角為9.5˚，19˚和28˚分別對應三種元件，即當入射波長從400到667 nm(約中心波長50%的寬度)，波長偏折角度皆不變。此外，實驗上我們也展示了三種具有不同數值孔徑(Numerical aperture, NA)值和直徑的可見光消色差聚焦超穎元件，在幾乎整個可見光波段內具有不變的焦距。在直徑為41.86微米的消色差超穎透鏡其在實驗上420 nm，550 nm和650 nm波長入射下，聚焦偏振轉換後的效率分別達到26.31％，19.71％和20.37％。此外，多根奈米棒集成共振單位元的設計經過數值優化，可實現從可見光到近紅外（400 nm到1400 nm）的50％以上的偏振轉換效率。因此，我們採用此多根奈米棒IRU構建多功能偏振轉產生器，在一束線性偏振光照明時，會同時產生六種常見的偏振態。轉向圓偏振和線偏振輸出光束的最大轉換效率分別達到80％和40％。我們利用集成共振單位元在連續寬頻寬上有效控制振幅和相位響應的方法為實現多功能全彩色元器件提供了前所未有的平台。

關鍵字

超穎介面 ； 超穎透鏡 ； 偏振產生器 ； 光束偏折器

並列摘要

With the incorporation of multiple elements or multiple resonances of nano-resonators into artifical plasmonic structures for optical components, these integrated-resonant units (IRUs), show a great ability for achieving controllable smooth and linear phase dispersion as well as amplitude manipulation over a continuous and broad bandwidth. Utilizing the property of IRUs design, we realize three achromatic deflectors showing constant steering angles of 9.5˚, 19˚, and 28˚ as the incident wavelength is varied from 400 to 667 nm (~50% bandwidth to the central wavelength). In, addition, three visible achromatic metalenses with various numerical aperture (NA) values and diameters are also experimentally demonstrated, displaying an unchanged focal length throughout almost the entire visible light wavelength range. The experimentally focusing efficiency of the achromatic metalens with diameter of 41.86μm achieves 26.31%, 19.71%, and 20.37%, respectively, at wavelengths of 420 nm, 550 nm, and 650 nm. Besides, a broadband versatile polarization generator is composed of multi-nanorod IRU design as building blocks numerically optimized to achieve above 50% conversion efficiency from visible to near-infrared (400 nm to 1400 nm). The versatile polarization convertor with high efficiency generates six common polarization states simultaneously upon one linear-polarized illumination. The maximal conversion efficiency for steered circular-polarized and linear-polarized output light beams reaches 80% and 40%, respectively. Our method with complete control of amplitude and phase response over continuously broad bandwidth provides an unprecedented platform in realizing multifunctional full-color meta-devices.

並列關鍵字

metasurface ； achromatic metalens ； polarization generator ； beam deflector

參考文獻

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