We propose the narrowband perfect absorbers with enormously high fabrication tolerance, which consists of a low-contrast grating and a finite distributed Bragg reflector (DBR) layer with an ultrathin absorbing medium (graphene). It is numerically shown that the proposed perfect absorber outperforms the previously proposed schemes in fabrication tolerance. According to the rigorous coupled wave analysis (RCWA) and coupled mode theory (CMT) fitting, over a considerably wide range of grating width and thickness, the proposed absorber provides a proper ratio of leakage rate to loss rate while preserving resonant condition, so that almost perfect absorption (>99.9%) can be obtained. This result is attributed to the strong electric field confinement in the DBR region rather than the grating layer owing to lower index of grating compared to DBR. In addition, without degrading the fabrication tolerance, the bandwidth of the proposed absorber can be controlled by the DBR thickness (the number of pairs) and a narrow absorbing bandwidth of sub-nanometer is achieved with 8.5 Si/SiO2 pair stacked DBR.
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机译:我们提出了具有极高制造公差的窄带完美吸收体,该吸收体由低对比度的光栅和有限分布的布拉格反射器(DBR)层组成,并具有超薄吸收介质(石墨烯)。数值显示,提出的理想吸收体在制造公差方面优于先前提出的方案。根据严格的耦合波分析(RCWA)和耦合模式理论(CMT)拟合,在相当宽的光栅宽度和厚度范围内,所提出的吸收器在保持谐振条件的同时,提供了合适的泄漏率与损耗率之比,因此可获得几乎完美的吸收(> 99.9%)。该结果归因于由于与DBR相比更低的光栅折射率,在DBR区域而不是光栅层中的强电场约束。另外,在不降低制造公差的情况下,可以通过DBR的厚度(对的数量)来控制所提出的吸收体的带宽,并且通过8.5 Si / SiO2对堆叠的DBR可以实现亚纳米级的窄吸收带宽。
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