Park Chang-Hyun, Yoon Yeo-Taek, Lee Sang-Shin
Department of Electronic Engineering, Kwangwoon University 447-1 Wolgye-Dong, Nowon-Gu, Seoul 139-701, South Korea.
Opt Express. 2012 Oct 8;20(21):23769-77. doi: 10.1364/OE.20.023769.
A nanophotonic polarization-independent visible wavelength filter is presented, incorporating a symmetric metal-dielectric resonant structure on quartz substrate, where a sub-wavelength grating, made up of a two-dimensional array of Al square sheets, is integrated with a Si(3)N(4) slab waveguide via an oxide layer. Incident light is orthogonally diffracted by the symmetric grating towards two directions of the grating groove, and then resonantly coupled to both transverse electric and transverse magnetic guided modes associated with the underlying waveguide, irrespective of light polarization. Polarization independent bandpass filtering was thus achieved around specific wavelengths, determined by the grating pitch and the effective index of the waveguide. Three devices, operating in the blue, green and red spectral bands, were built through design and analysis drawing upon the finite-difference time-domain method. The devices, DEV I, II, and III, were constructed with grating pitches of 285, 355 and 395 nm, respectively, while the core was 100 nm thick. They were inspected to function as an efficient bandpass filter, centered at 460, 560 and 610 nm, with bandwidths of about 13, 14 and 17 nm, respectively; the peak transmission efficiencies were consistently over 85%. Furthermore, the transfer characteristics, insensitive to light polarization, were satisfactorily confirmed for normal incidence.
本文提出了一种纳米光子偏振无关可见波长滤波器，它在石英衬底上集成了对称的金属 - 介质谐振结构，其中由二维铝方片阵列构成的亚波长光栅通过氧化层与Si(3)N(4)平板波导集成。入射光被对称光栅沿光栅槽的两个方向正交衍射，然后无论光的偏振如何，都与底层波导相关的横向电模和横向磁模谐振耦合。因此，在由光栅间距和波导有效折射率决定的特定波长附近实现了偏振无关带通滤波。通过基于时域有限差分法的设计和分析，制造了三个分别在蓝、绿和红光谱带工作的器件。器件DEV I、II和III的光栅间距分别为285、355和395 nm，而纤芯厚度为100 nm。经检测，它们可作为高效带通滤波器，中心波长分别为460、560和610 nm，带宽分别约为13、14和17 nm；峰值传输效率始终超过85%。此外，对于正入射，令人满意地证实了其对光偏振不敏感的传输特性。
