Optical Grating Fabrication via Segmented Photoresist Masking
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Solution Overview
Problem
Conventional optical grating fabrication methods often result in geometrical discrepancies, such as varying trough widths, depths, and profiles, which degrade the optical efficiency and coupling efficiency of the grating.
Innovation Solution
A method involving a first optically transparent layer, a stop layer configured to be invisible to light, and a second optically transparent layer with discrete ridges spaced by a pitch, decoupling the pitch from the height of the ridges and troughs, allowing for precise control of geometry and improved optical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photoresist mask fabrication is used, then manufacturing process is simple, but manufacturing precision of grating geometry deteriorates due to varying trough widths, depths, and profiles
Solution Approach 1:
The fabrication process is segmented into multiple sequential steps: forming the photoresist mask with lines and apertures, depositing the first core material layer, depositing the second core material layer through apertures, and removing the mask. This segmentation allows each step to be optimized independently, achieving precise control over trough geometry (width, depth, profile) while maintaining overall process manageability
Solution Approach 2:
The photoresist mask is formed in advance with precisely defined lines and apertures before any core material deposition. This preliminary action establishes the exact geometric template for the grating structure, ensuring that subsequent material deposition follows the desired pitch and profile specifications, thereby achieving high manufacturing precision
2Reliability
If pitch and depth are closely controlled to achieve high coupling efficiency, then optical performance improves, but manufacturing complexity increases
Solution Approach 1:
Different regions of the grating structure are formed with different materials and properties: the first core material layer forms the ridge regions while the second core material layer forms the trough regions. This local differentiation allows independent optimization of each region's properties to achieve the desired coupling efficiency and optical performance
Solution Approach 2:
The invention changes the approach from controlling pitch and depth as continuous parameters to defining them through discrete geometric features (line widths, aperture sizes, layer thicknesses). This parameter transformation enables more precise control over the effective pitch and trough depth, directly improving coupling efficiency through better-defined geometric parameters
Data Source
AI summary
A method and system for providing an optical grating are described. The optical grating is configured for light of a wavelength and includes a first optically transparent layer, a stop layer on the first optically transparent layer, and a second optically transparent layer on the stop layer. The first optically transparent layer is continuous and includes a material. The second optically transparent layer also includes the material. The second optically transparent layer also includes a plurality of discrete ridges spaced apart by a pitch. The stop layer is configured to be invisible to the light.