An optoelectronic device includes a display configured to emit first optical radiation in a first wavelength band through a front surface of the display. A planar optical waveguide, which is transparent in the first wavelength band, is overlaid on the display and is configured to guide second optical radiation in a second wavelength band along a direction transverse to the front surface. One or more diffractive structures are formed in the planar optical waveguide so as to couple the guided second optical radiation between the planar optical waveguide and a region in front of or behind the display.