Compact Focusing Grating Couplers Between Optical Fibers and Silicon-on-Insulator Photonic Wire Waveguides

We present compact and broadband grating couplers in silicon-on-insulator, between single-mode fiber and nanophotonic waveguides. Curved gratings allow for a very short transition between wide waveguides and photonic wires, resulting in very compact devices.

1 Introduction

Using high refractive index contrast materials is the route towards ultra-dense photonic integrated circuits. The last few years, a lot of very compact components were demonstrated in Silicon-on-Insulator (SOl) [1]. For this high-index contrast material system, CMOS-fabrication processes can be used, allowing for volume fabrication. An important problem remains the interface with the outside world. The large difference in mode-size between a singlemode optical fiber and nanophotonic on-chip waveguides results in large coupling losses and high packaging costs.