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 ISIPP 50G platform, combined with custom post-processing including an HF vapor release step. The coupler exhibits a 1 dB bandwidth of35 nm at $\lambda=1550nm,$ 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 $\sim 30\times 20\mu m^{2}$, the coupler can serve as basis for a new generation of compact standard Silicon Photonic MEMS library components.