Compact mode converter on SOI based on a polygonal subwavelength grating structure.

In this Letter, we design and experimentally demonstrate compact mode converters with a lightning-like and arrow-like polygonal subwavelength grating (SWG) structure on a silicon-on-insulator (SOI) platform, which can convert the TE mode to the TE and TE modes, respectively. The footprints of the proposed TE and TE mode converters are only 4.44 × 1.3 and 5.89 × 1.8 µm, respectively. The experimental results show the mode converters have a low insertion loss (<1 dB) and a broad bandwidth (>50 nm). The measured cross talks of the TE and TE mode converters are -7.2 dB and -10.3 dB, respectively. In addition, the proposed mode converters with the SWG structure have the advantage in fabrication, since only a one-step full-etching process is required.