Capacitive MEMS Spatial Light Modulator for Phased-Array Beam Steering
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Solution Overview
Problem
Optical phased-array systems, particularly in LIDAR, face challenges with mechanical SLMs due to their bulkiness and limited speed, while DMD-based SLMs struggle with achieving large scan angles efficiently due to size constraints and damping issues with narrow ribbons.
Innovation Solution
A capacitive microelectromechanical system (MEMS) device with a ribbon-type spatial light modulator featuring a damping structure and air-gaps to enable fast beam steering and large scan angles, along with an efficient method of driving MEMS pixels in a repetitive pattern to steer light beams effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a mechanical SLM with a spinning or moving mirror is used, then the device can steer light beams, but the device becomes bulky and the beam steering speed is limited due to the large mass of the mirror
Solution Approach 1:
The patent replaces the traditional mechanical mirror system with a MEMS-based spatial light modulator that uses electrostatic forces to deflect ribbons. This substitution of mechanical systems with electrostatic actuation enables faster beam steering speeds while reducing the mass of moving parts, directly resolving the contradiction between steering speed and mirror mass.
Solution Approach 2:
The patent changes the physical parameters of the deflectable elements from large mirrors to narrow ribbons with dimensions on the order of a few micrometers. This parameter change in size and mass allows for significantly faster response times while maintaining the light steering function.
2Speed
If a DMD-based SLM with microscopic mirrors is used, then beam steering speed improves, but achieving large scan angles requires small DMD dimensions which makes it difficult to maintain the speed advantage
Solution Approach 1:
The patent uses thin ribbon structures that can be electrostatically deflected to large angles. These flexible thin film structures achieve large scan angles without requiring the entire DMD device to be small, maintaining the speed advantage while enabling large angular deflections through the flexible nature of the ribbons.
Solution Approach 2:
The patent employs dynamically deflectable ribbons that can achieve large scan angles through electrostatic actuation. The dynamic response of these thin structures allows for both large angular deflections and fast response times, resolving the contradiction between scan angle size and device dimensions.
3Length of moving object
If narrow ribbons are used in DMD-based SLM to achieve large scan angles, then the scan angle increases, but damping issues arise that make it difficult to maintain speed advantage
Solution Approach 1:
The patent introduces a damping structure as an intermediary element that provides controlled damping to the narrow ribbons. This damping structure enables the narrow ribbons to achieve large scan angles while maintaining fast response speeds by controlling the damping characteristics, preventing excessive oscillations that would slow down the response.
4Length of moving object
If the ribbon width is reduced to achieve large scan angles, then the scan angle increases, but the ribbons become prone to snap-down issues
Solution Approach 1:
The patent implements a damping structure that acts as a cushioning mechanism to prevent snap-down of the narrow ribbons. This beforehand cushioning provides controlled damping that prevents the ribbons from snapping down unexpectedly, ensuring reliable operation while maintaining the narrow ribbon dimensions necessary for large scan angles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for rapid and precise beam steering with large scan angles, improving the dynamic response and preventing snap-down issues, enabling high-speed operation without sacrificing damping, thus enhancing the performance of phased-array applications like LIDAR systems.
Implementation Method 1
each of the plurality of movable members including a top electrode and being configured to deflect towards the bottom electrode by electrostatic force
Implementation Method 2
an electrically permeable damping structure formed over the bottom electrode... enabling fast beam steering and large scan angles
Data Source
AI summary
A capacitive micro-electromechanical system (MEMS) structure or device and methods of making and operating the same are described. Generally, the MEMS device provides a large stroke while maintaining good damping, enabling fast beam steering and large scan angles. In one embodiment, the capacitive MEMS device includes a bottom electrode formed over a substrate; an electrically permeable damping structure formed over the bottom electrode, the electrically permeable damping structure including a first air-gap and a dielectric layer suspended above and separated from the bottom electrode by the first air-gap; and a plurality of movable members suspended above the damping structure and separated therefrom by a second air-gap, each of the plurality of movable members including a top electrode and being configured to deflect towards the bottom electrode by electrostatic force. Other embodiments are also described.