An optical coupling system includes an optical signal source to provide an optical signal from an aperture. The system also includes a substantially planar high-contrast grating (HCG) lens to convert an optical mode of the optical signal to provide a converted optical signal having a mode-isolating intensity profile. The system further includes an optical element to receive the converted optical signal. The optical signal source and the substantially planar HCG lens can be arranged to substantially mitigate coupling of a reflected optical signal associated with the converted optical signal that is reflected from the optical element to the aperture of the optical signal source based on a reflected mode-isolating intensity profile.