Ultra compact, broadband tunable optical bandstop filters based on a multimode one dimensional photonic crystal waveguide.
In this paper, ultra compact, broadband tunable optical bandstop filters (OBSFs) based on a multimode one dimensional photonic crystal waveguide (PhCW) are proposed and systematically investigated. For the wavelengths in the mini stopband, the input mode is coupled to a contra propagating higher order mode by the PhCW and then radiates in a taper, resulting in a stopband at the output with low backreflection at the input. Three dimensional finite difference time domain method is employed to study the OBSFs. The influence of main structural parameters is analyzed, and the design is optimized to reduce the back reflection and band sidelobes. Using localized heating, we can shift the stopband and tune the bandwidth continuously by cascading the proposed structures. Due to the strong grating strength, our device provides a more compact footprint (40 mm x 1 mm) and much broader stopband (bandwidth of up to 84 nm) compared to the counterparts based on microrings, long period waveguide gratings, and multimode two dimensional PhCWs.
Optics express