Patent attributes
An optical coupling device can couple incident light, propagating orthogonal to a layered structure, into a layer of the layered structure. The device can include a lens having a lens central axis. The lens can focus a first beam to form a converging second beam. The first beam can have a first beam central axis that is offset from the lens central axis. The second beam can have a second beam central axis that is angled with respect to the first beam central axis. A planar grating can redirect the second beam to form a converging third beam. The third beam can have a third beam central axis that is parallel to a plane of the grating. Offsetting the first beam central axis from the lens central axis in this manner can help relax wavelength, manufacturing, and/or alignment tolerances, compared to a configuration in which there is no offset.