Highly Efficient Grating Couplers with Mode Conversion Functions

In this work, we show the possibility of combining grating couplers and mode converters, both with a high efficiency. The proposed devices are very compact with no extra fabrication efforts required. We have shown that the LP01, LP11a, LPilb and LP21b modes in an optical fiber can be successfully excited directly from the proposed grating couplers, which have the fundamental mode as an input from an integrated waveguide. It is shown the overall efficiency could be as high as 50%.