Optical assembly with diffractive optical element

An optical assembly of the present invention includes (a) a crystalline substrate (101) having a top planar surface (101a) and a crystalline plane angle; (b) at least one groove (102) defined in the top planar surface and having side walls (104) extending from an edge (315) of the substrate to a terminal end (103), the groove (102) having a first facet (105) at the terminal (103), the first facet (105) having a first angle relative to the top planar surface, the first facet (105) being reflective; (c) an optical conduit (110) having an optical axis and an end face optically coupled with the first facet; (d) a waveguide (131); and (e) a diffractive optical element (DOE) (140) disposed above the first facet and configured to couple light between the waveguide and the optical conduit as reflected by the first facet.