From a reliable source wrt to the Cai patent:

The application is written around the use of an "Optical Multi-die interconnect bridge" to optically connect two parts of an optoelectrical circuit (for example, the MUX and DeMUX circuits of a Transceiver.)

None of the claims are written around the mirror or lens but an image is provided that includes a surface mounted chiplet having one or more lasers and for which the lasers may be coupled to a waveguide or device on a substrate below via a reflector/lens.  This is not really what POET is doing with the mirrors generally in a same plane with a planar waveguide layer formed in a substrate.  The Celestial image shows the mirror as part of a chiplet mounted on the surface.  No description is provided on the formation of the mirror, or the details of the incorporation of a lens.

Generally speaking, there are quite a few applications and patents that include mirrors and reflectors.