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A Tunable Semiconductor‐Based Transmissive Metasurface: Dynamic Phase Control with High Transmission Level
Laser & Photonics Reviews ( IF 11.0 ) Pub Date : 2020-05-14 , DOI: 10.1002/lpor.201900353 Ali Forouzmand 1 , Hossein Mosallaei 1
Laser & Photonics Reviews ( IF 11.0 ) Pub Date : 2020-05-14 , DOI: 10.1002/lpor.201900353 Ali Forouzmand 1 , Hossein Mosallaei 1
Affiliation
Herein, a tunable semiconductor‐based metasurface, based on electro‐optical modulation of an array of geometrically‐fixed silicon (Si) nanobars, sandwiched between two distributed Bragg reflectors (DBRs) is proposed. A flat‐top transmission spectrum with a steep phase profile, which turns out to be essential to realize a highly‐efficient spatial light modulator in transmission mode, is formed by excitation of two spectrally close Fabry‐Pérot‐type and guided‐mode resonances. The refractive‐index of Si nanobars is electrically modulated by the injection of electrons and holes using a P–I–N junction configuration, considered along each nanobar. It is theoretically demonstrated that wide phase agility of 215° and transmission amplitude higher than 0.6 (with an average of ≈0.83) can be accomplished at the operating wavelength of ≈1.55 µm. This wide‐range tunability is realized by introducing free electron and hole carrier densities of ∆N = ∆P = 5 × 1018 cm−3 accompanied with Si refractive‐index‐change of ∆nSi = 0.01. The transmission phase of each unit cell can be separately controlled, which in turn allows to design a tunable meta‐array with real‐time beam control. As a proof of concept, a dynamic focusing metalens with an adjustable focal length is designed and numerically investigated.
中文翻译:
可调谐的基于半导体的透射超表面:具有高透射水平的动态相位控制
在此,提出了一种基于可调谐半导体的超表面,该超表面基于几何固定的硅(Si)纳米棒阵列的电光调制,该阵列固定在两个分布式布拉格反射器(DBR)之间。通过激发两个光谱上接近的法布里-珀罗型和导模共振,形成了具有陡峭相位分布的平顶透射光谱,这对于在透射模式下实现高效空间光调制器至关重要。硅纳米棒的折射率是通过沿每个纳米棒考虑的P–I–N结结构注入电子和空穴而进行电调制的。从理论上证明,在约1.55 µm的工作波长下,可以实现215°的宽相位捷变和大于0.6的透射幅度(平均≈0.83)。N = ∆ P = 5×10 18 cm -3,伴随着Si折射率的变化∆ n Si = 0.01。每个晶胞的传输阶段可以单独控制,从而可以设计带有实时波束控制的可调元阵列。作为概念的证明,设计并数值研究了焦距可调的动态聚焦金属。
更新日期:2020-05-14
中文翻译:
可调谐的基于半导体的透射超表面:具有高透射水平的动态相位控制
在此,提出了一种基于可调谐半导体的超表面,该超表面基于几何固定的硅(Si)纳米棒阵列的电光调制,该阵列固定在两个分布式布拉格反射器(DBR)之间。通过激发两个光谱上接近的法布里-珀罗型和导模共振,形成了具有陡峭相位分布的平顶透射光谱,这对于在透射模式下实现高效空间光调制器至关重要。硅纳米棒的折射率是通过沿每个纳米棒考虑的P–I–N结结构注入电子和空穴而进行电调制的。从理论上证明,在约1.55 µm的工作波长下,可以实现215°的宽相位捷变和大于0.6的透射幅度(平均≈0.83)。N = ∆ P = 5×10 18 cm -3,伴随着Si折射率的变化∆ n Si = 0.01。每个晶胞的传输阶段可以单独控制,从而可以设计带有实时波束控制的可调元阵列。作为概念的证明,设计并数值研究了焦距可调的动态聚焦金属。