Zaman Sameia, Hassan Mohammad Muntasir, Hasanuzzaman M, Baten Md Zunaid
Opt Express. 2020 Aug 17;28(17):25007-25021. doi: 10.1364/OE.399505.
Inspired by the morphology of Coscinodiscus species diatom, bi-layered photonic structures comprised of dielectric-filled nano-holes of varying diameters have been designed and analyzed to enhance and tune absorption characteristics of GaAs-based thin-film photonic devices. Finite difference time domain-based numerical analysis and effective medium approximation based theoretical calculations show that by adjusting diameter and areal density of the nano-holes of the two layers, the peak absorption wavelength can be tuned over a wide spectral range, while attaining a maximum peak-absorptance value of about 97% and a maximum absorption bandwidth of ∼ 190 nm. The maximum enhancement factor of the bi-layered structure is about 11% higher than the value obtained for its equivalent single-layered counterpart over the near-ultraviolet to visible regime of the spectra. High absorptance over a wide-angle for TM polarization and tunable angle-dependent absorption characteristics for TE polarization are also obtained for the proposed ultra-thin absorbers. It has been shown that instead of having misaligned pore-centers as in Coscinodiscus species diatoms, a bi-layered structure designed with layers of identical lattice constant offers significant flexibility in terms of design and practical realization of thin-film photonic devices.
受圆筛藻属硅藻形态的启发，设计并分析了由不同直径的电介质填充纳米孔组成的双层光子结构，以增强和调节基于GaAs的薄膜光子器件的吸收特性。基于时域有限差分的数值分析和基于有效介质近似的理论计算表明，通过调整两层纳米孔的直径和面密度，可以在很宽的光谱范围内调谐峰值吸收波长，同时获得约97%的最大峰值吸收率和约190 nm的最大吸收带宽。在光谱的近紫外到可见光范围内，双层结构的最大增强因子比其等效单层结构的值高约11%。对于所提出的超薄吸收体，还获得了TM偏振在广角范围内的高吸收率以及TE偏振的可调角度依赖吸收特性。研究表明，与圆筛藻属硅藻中孔中心未对齐的情况不同，具有相同晶格常数层的双层结构在薄膜光子器件的设计和实际实现方面提供了显著的灵活性。
