Optimized fabrication of subwavelength slanted gratings via laser interference lithography and faraday cage-assisted etching

Abstract

Subwavelength slanted gratings are crucial components in devices such as augmented reality systems and optoelectronic sensors due to their high diffraction efficiency and compact design. However, their fabrication is often hindered by high costs and limited structural control. This paper presents a novel fabrication method that combines a laser interference lithography (LIL) process, optimized using a two-dimensional lithography simulation model, with a Faraday cage-assisted reactive ion etching (RIE) process. The simulation model integrates exposure intensity analysis under the standing wave effect with photoresist contrast curve characteristics, enabling accurate simulation of photoresist patterns and providing precise feedback on exposure time and the angle between exposure light beams to achieve precise control of key parameters, such as period and duty cycle. Compared to traditional models, it reduces complexity while delivering high accuracy. The LIL process optimized by this model achieves negligible period error and a duty cycle error $\le 0.01$. Faraday cage-assisted RIE further enhances control over grating height and tilt angle, achieving near-zero deviations. This scalable and cost-effective method provides a reliable solution for fabricating high-precision subwavelength slanted gratings, advancing their practical applications in sophisticated optical systems.