Microlens Arrays Correct Fabrication-Induced Curvature in Micromirror-Based Spatial Light Modulators, Achieving Near 100% Fill Factor

High-speed control of light is crucial for advances in areas like holographic displays and optogenetics, but creating devices that can accurately shape light beams presents significant challenges. Munkyu Kang, Elizabeth Murray, Leyla A. Kabuli, and colleagues at the University of California, Berkeley, address this problem by developing a new method for correcting distortions in micromirror-based spatial light modulators. The team demonstrates that stress during fabrication often causes these tiny mirrors to curve, degrading performance, but a carefully designed microlens array can refocus light onto the centre of each mirror, effectively eliminating these distortions. This innovative approach achieves nearly 100% fill factor and dramatically improves the accuracy of the generated light patterns, increasing brightness by a factor of eight and boosting the correlation of the imparted phase profile from 0. 11 to 0. 85, paving the way for scalable, high-fidelity wavefront control.

Microlens Arrays Correct Mirror Fabrication Curvature

Researchers detail a technique for correcting fabrication-induced curvature in micromirror devices, specifically spatial light modulators used for creating dynamic optical patterns. The study explains methods used to model light propagation, align the correction system, and verify its effectiveness, utilizing the angular spectrum method to simulate curved mirror surfaces and reflected wavefronts. Precise alignment between the microlens array and the spatial light modulator is critical, established through transmission imaging and refined with Digital Holographic Microscopy. Matching the pitch of the microlens array to the spatial light modulator is essential for uniform correction across the surface, validating the implementation and demonstrating the importance of accurate modeling, precise alignment, and pitch matching for improving device performance.

Stress Compensation in Micromirror Array Fabrication

Researchers have developed a novel compensation method to address challenges in fabricating high-speed spatial light modulators for computer generated holography. Focusing on piston-motion micromirror arrays capable of exceeding 10kHz refresh rates, the study addresses stress-induced curvature in larger mirrors, which degrades optical performance by focusing light instead of shifting its phase. Scientists engineered a pitch-matched microlens array to focus light onto the center of each micromirror, optically compensating for deformation and maintaining high diffraction efficiency regardless of mechanical fill factor. Experiments with intentionally bowed mirrors demonstrated a dramatic improvement in phase profile correlation, increasing from 0.

11 to 0. 85 with the microlens array, and enhanced the brightness of a holographically-generated single spot by a factor of 8. This hybrid optical-electromechanical strategy provides a scalable path toward high-fidelity wavefront control for adaptive optics, dynamic spectroscopy, and real-time holographic displays.

Microlens Array Corrects Mirror Curvature Distortion

Scientists have developed a novel compensation technique to significantly improve the performance of high-speed spatial light modulators used in applications like holographic displays and optogenetics. The research addresses stress-induced curvature in micromirrors, which degrades the quality of projected light, with fabricated arrays exhibiting bowing causing light reflection to focus 0. 85 millimeters from the mirror surface. To counteract this, the team introduced a pitch-matched microlens array focusing light onto the central region of each mirror, effectively avoiding distortions and achieving near 100% optical fill factor independent of mechanical limitations.

Wave propagation simulations and experimental validation demonstrated a substantial improvement in phase profile accuracy, increasing the Pearson correlation coefficient from 0. 11 to 0. 85, and enhanced the brightness of a holographically-generated single spot by a factor of 8, demonstrating a scalable path toward high-speed, high-fidelity wavefront control.

Micromirror Holography Corrects Distortion With Microlenses

This research demonstrates a method for significantly improving the performance of micromirror-based spatial light modulators, crucial components in dynamically creating three-dimensional holograms. Scientists addressed the challenge of mirror curvature, a common issue in high fill factor designs that degrades holographic image quality, by integrating a pitch-matched microlens array focusing light onto the center of each mirror, effectively correcting distortions and achieving near 100% optical fill factor. Experimental results confirm the effectiveness of this technique, showing an improvement in the correlation between the intended and actual phase profile from 0. 11 to 0. 85, and an eight-fold increase in the brightness of holographically generated spots, restoring phase uniformity on curved mirror surfaces and offering a scalable path towards high-speed, high-fidelity wavefront control for applications including adaptive optics, holographic displays, and optogenetics.