A strategy for polarization-independent ultra-narrowband filters by sub-wavelength all-dielectric meta-materials

Ultra-narrowband light filtering is with wide applications in display, image and optical measurement devices. Here, we theoretically propose and show a new and simple strategy for achieving notch filters by sub-wavelength all-dielectric meta-materials (ADMMs). The ADMM is comprised of a triple-layered high/low/high-index dielectric structure. Similar to the plasmonic resonances existed in the metallic meta-materials, strong optical field resonances have been observed in this ADMM. Dual-band reflective notch filtering phenomenon is achieved. Spectral bandwidth down to 3 nm and the spectral contrast reaching 97% are obtained. Moreover, the polarization-independent response is simultaneously achieved in this ADMM. Furthermore, high spectral tunability for the observed ultra-narrowband filtering is obtained via tuning the structural parameters.