Coupled-Wave Theory Improvements for Diffractive Optics

The objective of this project is to develop improved simulation and modeling codes for diffractive optics based on Rigorous Coupled-Wave (RCW) theory. Phase 1 will focus on the following tasks: (1) Develop and test a new algorithmic method for reliably simulating grating structures having sloped and curved surfaces (e.g., tapered lamellar gratings, arrays of circular posts). (2) Explore and test a method for more accurately and efficiently simulating electromagnetic field singularities at grating edges. (3) Develop and test grating design software based on generic functional modeling code, which automatically generates derivative information from MATLAB numeric equations. (This has applicability for automated grating design optimization, metrology, and sensitivity analysis.) (4) Evaluate options for applying parallel computing (multi-core, GPU, distributed computing) to accelerate the runtime performance of MATLAB-based RCW code. (Tasks (1), (2) and (3) will be performed by KJ Innovation and Task (4) will be performed by Sandia National Laboratories.). KJ Innovation currently produces a MATLAB-based RCW software product, the Grating Diffraction Calculator (GD-Calc), which has very general capabilities for simulating uniperiodic and biperiodic grating geometries (e.g., any number of grating layers and materials, arbitrary user-defined geometries). As currently implemented, the code represents sloped and curved surfaces using a staircase approximation, which has limited accuracy and is unsuitable for evaluating internal fields near grating surfaces. Also, grating structures having sharp edges give rise to field singularities, which can limit simulation accuracy and speed. Under Phase 2 and 3 these limitations will be overcome with a GD-Calc successor product based on the results of Phase 1. The new product will be designed to work with functional modeling code (a separate software product) to enable grating design optimization and sensitivity analyses similar to that commonly used in lens design. It will also be designed to take full advantage of modern computer hardware, e.g., to enable fast simulation of complex grating structures in an optimization loop. The software will be useful for a broad range of commercial applications including, but not limited to, those within the mission of DOEs Office of Science.