A flat illuminator having substantially reduced or no diffractive artifacts may be realized by using a partially reflective, embedded layer of extraction features, such as partially reflective facets or partially reflective bumpy surface, buried with substantially matching refractive index on both sides of layer. Implementations may be used in creating infrared (IR) illumination, either as a frontlight unit (FLU) or backlight unit (BLU), as well as for supporting a floating image of IR illumination in a retroreflective, reconvergent imaging or a retroimaging application.