A grating assisted optical waveguide for use in free space optical detection is disclosed. High speed, high sensitivity, large field of view, and relaxed tolerance on alignment are enabled. The grating converts a free space incoming optical beam into guided mode. Converted optical signals propagate along the waveguide, and can be directed to an optical detector. As such, the optical intensity at the active area of the detector is increased significantly. A number of optical beam converter gratings for free space light collection can be used, including linear and ring structure gratings, chirped gratings, and multilayer gratings. Such a grating assisted optical waveguide can be used, for example, in a digital wireless multimedia system, where digital content is wirelessly transmitted from a source to a target destination, such as home-based video and audio entertainment systems.