傳統上的金屬電漿子透鏡由於製程上與幾何尺寸上的限制，限制了透鏡上的相位控制 (小於0.5π)，無法有效的操控光學相位來達成聚焦元件的最佳化，所以本論文提出了一種金屬平面透鏡的聚焦元件，由圓形孔洞和同心圓孔洞組成。由於低深寬比的圓形孔洞僅能提供較低相位補償，因此我們設計另一種同心圓孔洞來提供另一個相位補償，圓形孔洞和同心圓孔洞在入射光的照射下可以產生局部和圓柱形表面電漿子。
這兩種模態在波導中的傳遞相位與孔徑幾何形狀有關，我們將這些孔徑設計為具有0到π的人工相位，利用雙曲相位公式，將圓形與同心圓孔置入在同心圓陣列中的不同位置，進而操控透鏡的波前。焦距與焦點大小隨著電漿子透鏡上的結構分布，可以適當地控制相位來得到小焦點尺寸 (入射波長的一半)。
我們還透過實驗證明了這種電漿子透鏡的聚焦特性，以驗證我們的設計，由於圓形和同心圓孔徑的圓形對稱性，這種類型的電漿子透鏡同時具有成為偏振不敏感器件的潛力。
關鍵字：電漿子，超穎透鏡，相位補償

An unconventional plasmonic lens which are both constructed by circular and annular apertures in the silver film is proposed to be a focusing device. The circular and annular apertures can induce localized and cylindrical surface plasmon modes with the incident light, respectively. Their propagation phase in the waveguide is related to aperture geometries. We design these apertures to have the artificial phase from zero to Pi and arrange the apertures in concentric arrays to manipulate the wavefront of lens. The focal length and size of focal spot are accompanied by the phase distribution on the plasmonic lens. The small focal spot size (half of wavelength) can be obtained by the proper manipulation of phase. We also demonstrate the focusing properties of this plasmonic lens experimentally to validate our design. Owing to the circular symmetry of circular and annular apertures, this type of plasmonic lens have a great potential to be a polarization-insensitive device.
KEYWORDS: Plasmonic, Metalens, Phase-compensation.

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