Long-Working-Distance Grating Coupler for Integrated Optical Devices

A novel grating coupler design is presented with its experimental demonstration. The grating can focus the outcoming light upward without the need for a lens or additional fabrication steps. The lenslike effect is introduced by applying a deformation to the grating stripes in order to add a phase map that matches the phase of the spherical wavefront coming from the fiber. The presented grating is designed for silicon photonics technology and has a working distance of 230 μm to a standard single-mode fiber. This long distance would introduce an excess loss of 9 dB with a standard grating, whereas with the long-working-distance grating, we demonstrate no extra loss with respect to the standard grating.