A grating-based backlight (200, 300) comprising: a light guide comprising: a plate light guide (220, 310) to guide light at a non-zero propagation angle; characterized in that the light guide is a grating-coupled light guide and further comprises: a grating coupler (230, 320) at an input of the plate light guide, the grating coupler to receive light from a light source and to diffractively redirect the light into the plate light guide at the non-zero propagation angle as guided light, wherein the grating coupler comprises diffractive features whose characteristics determine the non-zero propagation angle, a first spread angle, and a second spread angle of the guided light, the first spread angle being an angle in a plane perpendicular to a surface of the plate light guide and the second spread angle being an angle in a plane parallel to the surface of the plate light guide; and wherein the grating-based backlight is a multibeam grating-based backlight and further comprises: an array of a multibeam diffraction gratings (250,330) adjacent to the surface of the plate light guide, each of the multibeam diffraction gratings configured to couple out a portion of the guided light as a plurality of light beams, a principal angular direction of a light beam of the light beam plurality being different from principal angular directions of other light beams of the light beam plurality. a light guide comprising: a plate light guide (220, 310) to guide light at a non-zero propagation angle; characterized in that the light guide is a grating-coupled light guide and further comprises: a grating coupler (230, 320) at an input of the plate light guide, the grating coupler to receive light from a light source and to diffractively redirect the light into the plate light guide at the non-zero propagation angle as guided light, wherein the grating coupler comprises diffractive features whose characteristics determine the non-zero propagation angle, a first spread angle, and a second spread angle of the guided light, the first spread angle being an angle in a plane perpendicular to a surface of the plate light guide and the second spread angle being an angle in a plane parallel to the surface of the plate light guide; and wherein the grating-based backlight is a multibeam grating-based backlight and further comprises: an array of a multibeam diffraction gratings (250,330) adjacent to the surface of the plate light guide, each of the multibeam diffraction gratings configured to couple out a portion of the guided light as a plurality of light beams, a principal angular direction of a light beam of the light beam plurality being different from principal angular directions of other light beams of the light beam plurality. a grating coupler (230, 320) at an input of the plate light guide, the grating coupler to receive light from a light source and to diffractively redirect the light into the plate light guide at the non-zero propagation angle as guided light, wherein the grating coupler comprises diffractive features whose characteristics determine the non-zero propagation angle, a first spread angle, and a second spread angle of the guided light, the first spread angle being an angle in a plane perpendicular to a surface of the plate light guide and the second spread angle being an angle in a plane parallel to the surface of the plate light guide; and wherein the grating-based backlight is a multibeam grating-based backlight and further comprises: an array of a multibeam diffraction gratings (250,330) adjacent to the surface of the plate light guide, each of the multibeam diffraction gratings configured to couple out a portion of the guided light as a plurality of light beams, a principal angular direction of a light beam of the light beam plurality being different from principal angular directions of other light beams of the light beam plurality.