Asymmetric Waveguide Gratings With Varying Height for Light Coupling

The patent applies asymmetry by designing grating structures with non-uniform heights across the substrate. Specifically, the grating structures have different heights at different locations, creating asymmetric profiles that optimize light coupling and distribution. This is achieved through selective etching processes that remove material to varying degrees across the grating array, transforming uniform structures into asymmetric ones with enhanced optical performance.

The patent implements local quality by varying the height of individual grating structures based on their specific location and function. Different regions of the substrate receive grating structures with tailored heights optimized for their local optical requirements. This localized optimization allows each grating structure to perform its specific function efficiently while maintaining overall system performance.

The patent applies preliminary action by first forming a uniform photoresist layer across the entire substrate before patterning. This initial uniform layer serves as a baseline that can then be selectively removed to create the varying heights. The preliminary deposition of the uniform photoresist simplifies the subsequent etching process, as the variation is achieved through selective removal rather than selective deposition, reducing manufacturing complexity.

The patent implements segmentation by dividing the grating fabrication into distinct stages: forming uniform photoresist structures, selectively removing photoresist in certain regions, and then etching the substrate through the remaining photoresist patterns. This segmented approach breaks down the complex task of creating varying heights into manageable steps, each with controlled parameters, thereby simplifying the overall manufacturing process.