Abstract: Embodiments described herein relate to improved waveguides with materials layers improving the optical properties of one or more surface regions of waveguides and methods of forming the same. In one embodiment, a waveguide is provided. The waveguide including a substrate, a grating disposed in or on the substrate, the grating comprising a plurality of structures defined by a plurality of trenches, a layer of silicon oxide or aluminum oxide disposed over the structures on the substrate. The layer is disposed over sidewalls and top surfaces of the structures, and a bottom surface of the trenches. The waveguide further includes a high index layer disposed over the layer. The high index layer is disposed over the sidewalls and the top surfaces of the structures, and the bottom surface of the trenches with the layer disposed in between the structures and the high index layer.

Abstract: A hot melt adhesive composition comprises at least one styrene block copolymer, at least one acid modified rubber, and a tackifying resin comprising at least one acid tackifying resin. The hot melt adhesive composition can be used to bond substrates. The invention further relates to an article comprising the hot melt adhesive composition, to the use of a combination of an acid modified rubber and an acid tackifying resin for improving the aged wet adhesiveness of a hot melt adhesive composition, and to the use of a non-acid tackifying resin having a softening point of at least 110° C. for improving the initial adhesiveness of a hot melt adhesive composition comprising a combination of an acid modified rubber and an acid tackifying resin.