摘要
智能化时代对超大容量、超高密度信息传输需求使得超窄带滤光片研究得到越来越多的重视。将具有类狄拉克点简并能带结构的光学超构材料引入传统共振腔结构的滤光片模型中,提出了一种零折射率效应与谐振效应相结合的复合滤光片结构。基于COMSOL Multiphysics软件的仿真结果表明,相比于单一缺陷态的滤光片,复合滤光片的透射峰带宽能够被显著压缩,同时又能保持高的峰值透过率。揭示了零折射材料所具备的零相位延迟及强色散特性是复合滤光片形成超窄带宽的内在原因,并探索了其带宽的窄带优化设计方案。基于超材料的复合超窄带滤光片可为密集波分复用提供一条新的技术途径。
Objective In a dense wavelength-division multiplexing(DWDM)system,the narrow-band filter is a core component ensuring the quality of information transmission,and its importance is self-evident.As data transmission continues to develop towards larger capacity and higher density,the DWDM system faces even greater challenges.To improve the utilization rate of optical fiber transmission channels,the number of multiplexing needs to be continuously increased,which leads to a continuous narrowing of the channel spacing.Therefore,the filters with high transmittance,ultra-narrow bandwidth,and large aperture have attracted increasing attention from researchers.Zero-index metamaterial(ZIM)possess a series of unique physical properties,and their zero-index characteristic only exists within a narrow frequency range.This characteristic is extremely beneficial for the design of ultra-narrow-band optical filters.For this purpose,an ultra-narrow-band compsite filter baseed on ZIM is designed.Methods Firstly,a ZIM material with a thickness of d_(2) is designed to be embedded in the resonant cavity of the filter to compose a composite filter(Fig.2).The degeneracy frequency ω_(d) of the ZIM is designed to be equal to the center frequency ω_(0) of the resonant cavity with a thickness of d_(1),that is,ω_(0)=ω_(d).Subsequently,the COMSOL Multiphysics software is used to simulate the transmission curve(Fig.3(a))of the composite filter and the electricfield distribution at the frequency of ω_(0)(Fig.3(b)and Fig.3(c)).Furthermore,the equivalent permittivity and permeability of the ZIM at the Dirac-like frequency point are calculated(Fig.4).Finally,in order to analyze the mechanism of the compression of the transmission bandwidth of the composite filter,the influence of the thickness d_(2) on the bandwidth of the composite filter is simulataed(Fig.5).Results and Discussions To compose a composite filter,a ZIM with a thickness of d_(2)=2.8μm is embedded in a resonant cavity with a defect of d_(1)=0.3μm(Fig.2(b)).The simulated results indicate that the resonant frequencies of these two cavities are nearly identical(Fig.3(a)).This phenomenon suggests that light with resonant frequency experiences almost no phase delay when passing through the ZIM material.Through further calculations and analyses,it is found that the equivalent refractive index of the ZIM approaches zero(Fig.4(a)).In such a situation,the transmittance of the composite filter is hardly affected by the thickness of the ZIM,which is consistent with that of a single line-defect filter without ZIM.At the resonant frequency of 195.9 THz,the full-width at halfmaximum(FWHM)of the proposed composite filter is only 70 GHz(Fig.4(b)).Compared with the 300-GHz FWHM bandwidth of a sigle line-defect filter,its bandwidth is compressed by a factor of approximately 4.5(Fig.4(b)),fully demonstrating the characteristics of ultra-narrowband filtering.Meanwhile,the quality factor of the composite filter is also significantly improved.Finally,by thoroughly calculating the influence of the thickness d_(2) on the bandwidth of the proposed composite filter,the simulated results show that the thickness of the ZIM has little effect on the resonance mode of the composite filter.Moreover,the ultra-narrowband characteristics of the composite filter can be optimized through the meticulous design of the ZIM thickness d_(2)(Fig.5).Conclusions The rapid growth in demand for ultra large capacity and high-density information transmission in the era of intelligence has led to increasing attention being paid to the research of ultra narrowband filters.An optical metamaterial with degenerate energy bands and Dirac-like point are introdeced into the traditional resonant cavity structure filter model,and a composite ultra-narrow-band filter that combines zero refractive index effect and resonant effect is proposed.The COMSOL Multiphysics software is used to simulate the transmission rate of the optical filter and its electric-field distribution.The simulation results show that when the Dirac-like frequency point coincides with the resonant frequency of the cavity,the zero-phase-delay characteristic and the strong dispersion characteristic of ZIM will work together,and the filtering bandwidth of the proposed filter can be significantly compressed.Specifically,a composite filter based on ZIM material with a thickness of 2.8μm and a 0.3μm-line-defect resonant cavity is designed.At the resonant frequency of 195.9 THz,the FWHM of the composite filter is only 70 GHz.Compared with the 300-GHz bandwidth of a single line-defect filter,its bandwidth is compressed by a factor of approximately 4.5,fully demonstrating the characteristics of ultranarrowband filtering.An in-depth analysis of the mechanism of bandwidth compression and explores the optimization design of ultra-narrow-band are also provided.The research results provide new technical ideas for the design and application of optical communication devices based on optical metamaterials.
作者
陈英
周晓霞
蔡力
CHEN Ying;ZHOU Xiaoxia;CAI Li(Department of Electronic information and Electrical engineering,Changsha University,Changsha 410022,China;Laboratory of Science and Technology on Integrated Logistics Support,College of Intelligence Science,National University of Defense Technology,Changsha 410073,China)
出处
《红外与激光工程》
北大核心
2025年第8期358-366,共9页
Infrared and Laser Engineering
基金
国家自然科学基金项目(61308005)
湖南省自然科学基金项目(2018JJ2455)。
关键词
超窄带滤光片
零折射率超材料
缺陷态
共振腔
ultra-narrow-band filter
zero-refractive index
the defective state
resonant cavity
作者简介
陈英,男,教授,博士,主要从事光电子器件及超快激光技术方面的研究;通讯作者:周晓霞,女,讲师,硕士,主要从事光电子器件方面的研究。
