Ultra-narrowband filter based on the metal-cladding resonant waveguide

The simple and effective optical filter is the significantly scientific and technical interest in optical signal processing and communication. Especially, the development of microsystem integration is limited in traditional optical filters, due to the complicated structure, small choice, large cost, etc. In this paper, we report an ultra-narrowband filter based on a metal-cladding resonant waveguide. Therein, the ultra-narrowband resonant mode is achieved based on the resonance screening of incident light and cavity modes. According to the experimental data, the full width at half maximum (FWHM) can reach less than 0.1 nm. Furthermore, the resonant peak of FWMH is determined by the thickness of the waveguide, and the resonant wavelength can be selected by changing the incident angle.