Design of reconfigurable on-chip mode filters based on phase transition in vanadium dioxide

On the basis of the phase transition between an insulator and a metal in vanadium dioxide (VO2), we propose ultracompact and broadband lower- and higher-order mode pass filters (LOMPF and HOMPF, respectively) for a multimode silicon waveguide supporting two transverse electric (TE) modes. Good performance of mode filtering can be maintained over a wavelength range of 100 nm. In addition, the two filters can be cascaded to achieve reconfigurable operation for both TE00 and TE01 modes, including TE00-pass, TE01-pass, all-pass, and all-block. The reconfigurable response of the proposed on-chip mode filter is helpful for flexible mode-division multiplexing applications.