窄刻槽亚波长金属波导光栅透射滤波研究

Study on Narrowband Transmission Filter Based on the Subwavelength Metal Waveguide Grating with Narrow Grooves

提出了一种窄刻槽亚波长金属波导光栅透射滤波器的设计,其工作原理是利用窄光栅刻槽取得低透射背景,再利用导模共振与表面等离子激元共振的混合产生峰值透射,进而实现良好的窄带透射滤波效应。研究发现,利用多模共振与表面等离子激元共振的混合模式,通过增加波导厚度即可实现性能良好的双通道透射滤波,在波长1 412和1 653nm处,峰值透射率分别为72.1%和63.6%。进一步分析表明,由于长波处磁场能量较多地局域在金属光栅层,峰值位置和峰值透射率受光栅深度变化影响显著;而短波处磁场能量较多地局域在波导层中,因此短波处峰值漂移对波导层厚度变化更为敏感。

The design approach of the transmission filter using the subwavelength metal waveguide grating with narrow grooves is proposed.The operational principle of the filter is that its low transmission background is obtained by using the metal grating with narrow grooves,and its transmission peak is achieved by using the hybrid Guided-Mode Resonance（GMR）and the Surface Plasmon Polariton（SPP）resonances.It is shown that by increasing the thickness of the waveguide layer,a dual-channel transmission filter with good filtering performance can be obtained based on the hybrid modes of multiorder GMR and SPP resonances.The transmission peaks of the dual-channels at 1 412 nm and 1 653 nm are 72.1% and 63.6%,respectively.Further analysis show that the peak transmission and its location of the filter at longer wavelength is mainly affected by the grating thickness.This is because that the energy of the magnetic field of the longer wavelength is mainly confined in the grating layer.For the transmission peak of the filter at the shorter wavelength,the energy of the magnetic field is mainly confined in the waveguide.Therefore,the shift of the transmission peak is sensitive to the variation of the waveguide thickness.