A bar collimator and a backlight system employ diffractive coupling to provide a collimated source of illumination to a backlight. The bar collimator includes a light guide and a diffraction grating disposed on a side of the light guide. The light guide is configured to guide light received from a light source as guided light. The diffraction grating is configured to diffractively couple out a portion of the guided light and to direct the diffractively coupled-out portion toward an input of a backlight as a collimated light having an extent corresponding to a length of the backlight input. A backlight system includes the bar collimator and further includes a light source and a backlight adjacent to the light guide of the bar collimator, the backlight being configured to receive collimated light from a diffraction grating of the bar collimator.