Silicon Photonic Broadband Suspended Directional Coupler

We demonstrate a broadband Silicon Photonic directional coupler that is entirely suspended in air. The device has been fabricated in a simplified Silicon Photonics process based on the standard IMEC ISIPP5OG platform, combined with custom post-processing including an HF vapor release step. The coupler exhibits a 1 dB bandwidth of 35 nm at lambda=1550 nm, and an insertion loss of 0.5 dB at 1560 nm, confirmed experimentally. With an extinction ratio of 25 dB at 1550 nm and a compact footprint of similar to 30 x 20 mu m(2), the coupler can serve as basis for a new generation of compact standard Silicon Photonic MEMS library components.