Hybrid-core co-planar waveguide mode multiplexer fabricated by multi-step photolithography for high-order-mode-passed guide mode manipulating

We propose a methodology for fabricating a hybrid-core planar waveguide mode multiplexer using multi-step photolithography and demonstrate the manipulation of the fundamental mode without affecting the high-order modes in the experiment. We design and fabricate the proposed mode multiplexer, and our experimental device provides coupling ratios for the fundamental mode that are higher than 92.0 % and 91.6 % for the transverse-electric (TE) and transverse-magnetic (TM) polarizations and the modal crosstalks are lower than −10.6 dB and −10.4 dB for the TE and TM polarizations, respectively, over the C + L band. The device is confirmed to be low sensitivity to the state of polarization. The proposed methodology can be further developed to realize the fabrication of a two-material system heterogeneous integrated photonic device.