Leaky-mode waveguide modulators with high deflection angle for use in holographic video displays

Abstract

Film display holograms typically diffract light over a wide enough view-angle to be viewed, directly, without intervening optics. However, all holographic video displays (with the exception of eye-tracked systems) must use optics beyond the hologram surface to overcome the challenges of small display extent and low diffraction angle by using some form of demagnification and derotation (i.e. angle magnification and optical multiplexing). We report a leaky mode waveguide spatial light modulator with sufficiently high angular diffraction to obviate the need for demagnification in scanned aperture systems. This high angle was achieved by performing a number of experiments to determine the depth of the annealed, proton-exchanged waveguide which corresponded to a maximized diffracted angle. Diffraction sweeps were recorded in excess of 19.5° (corresponding to only 70 MHz of input bandwidth) for 632.8 nm light which is above the 15° required for direct view display. Device geometries are proposed which might achieve greater than 20° of total angular sweep for red, green, and blue light.