Methods for fabricating an optical waveguide and a display device and photomask used therein

A method for fabricating a display device comprising:

• providing a photomask and forming a first light curing resin layer on a first transparent substrate, wherein the photomask has light blocking structures that are regularly distributed;
• placing the photomask on the first light curing resin layer;
• irradiating and curing the first light curing resin layer to have a first curing level and a corresponding first refractive index with incident light through the photomask and the light blocking structures, wherein the first curing level and the first refractive index are periodically distributed;
• removing the photomask from the first light curing resin layer to form an optical waveguide with the first light curing resin layer having a periodically distributed the first curing level and the first transparent substrate;
• and
• connecting a body with a display module and the optical waveguide to form a display device;
• wherein after the step of removing the photomask from the first light curing resin layer and before the step of forming the optical waveguide with the first light curing resin layer having the periodically distributed the first curing level and the first transparent substrate, at least one light curing process is performed, and the at least one light curing process comprises:
• forming a second light curing resin layer on a latest formed the light curing resin layer;
• placing the photomask on a latest formed the second light curing resin layer and irradiating and curing the latest formed the second light curing resin layer to have a second curing level and a corresponding second refractive index with the incident light through the photomask and the light blocking structures, wherein the second curing level and the second refractive index are periodically distributed;
• and
• removing the photomask from the latest formed the second light curing resin layer, wherein in the step of forming the optical waveguide with the first light curing resin layer having the periodically distributed the first curing level and the first transparent substrate, the optical waveguide with the first light curing resin layer having the periodically distributed the first curing level, the second light curing resin layer having the periodically distributed the second curing level, and the first transparent substrate is formed;
• gratings that are spaced at uniform intervals along a direction parallel to a surface of the first transparent substrate are formed between the first transparent substrate and the first light curing resin layer;
• wherein the gratings and the light blocking structures have same positions along a direction parallel to the surface of the first transparent substrate;
• wherein the first light curing resin layer has completely-cured areas that separate from each other, and the completely-cured areas and the gratings are alternately arranged on the first transparent substrate.