Mirror-Enhanced MEMS Spatial Light Modulator for Long Wavelength Steering
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Solution Overview
Problem
MEMS-based spatial light modulators (SLMs) face challenges in steering light with longer wavelengths, requiring increased stroke lengths that complicate manufacturing and affect performance, especially in LIDAR applications where mechanical mirrors are slow, expensive, and fragile.
Innovation Solution
Incorporating a mirror and/or dispersive elements into the MEMS-based SLMs to enhance light steering, allowing operation at longer wavelengths without increasing stroke lengths, and using a flat mirror to reflect light back onto the modulation elements, increasing phase modulation and enabling efficient light steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the stroke length of MEMS-based SLM is increased to steer longer wavelengths, then the light steering capability for longer wavelengths is improved, but the manufacturing complexity and device fragility increase
Solution Approach 1:
A fixed mirror is introduced as an intermediary element in the optical path. The mirror reflects light back through the modulation elements, effectively doubling the optical path length and phase modulation without requiring increased physical stroke length of the MEMS ribbons. This mediator enables longer wavelength operation while maintaining the original compact MEMS structure.
Solution Approach 2:
The optical path is folded back through the use of a mirror, effectively utilizing the return path dimension. Light travels through the modulation elements twice (forward and backward), doubling the phase modulation effect without increasing the physical dimension of the MEMS device. This dimensional approach allows longer wavelength steering capability while maintaining compact form factor.
2Speed
If mechanical mirrors are used to steer light in LIDAR systems, then light steering is achieved, but the system becomes slow, expensive, and fragile
Solution Approach 1:
The patent replaces traditional mechanical steering mirrors with a MEMS-based spatial light modulator using electrostatically actuated ribbons. These ribbons can be individually addressed and actuated at high speeds with no moving parts beyond the micro-scale ribbon deflection, eliminating the mechanical inertia and fragility of traditional mirrors while enabling random-access pointing capability.
Solution Approach 2:
The modulation elements use thin ribbon structures with reflective surfaces that can be electrostatically deflected. These flexible thin-film ribbons are suspended over gaps and can be individually actuated by applying voltage between the ribbon electrode and base electrode, providing fast, reliable, and cost-effective light steering without the mechanical complexity of traditional mirror systems.
3Measurement precision
If the stroke length is increased to maintain 2π phase operation at longer wavelengths, then the phase modulation capability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The fixed mirror acts as a mediator that doubles the effective optical path length through the modulation elements. This allows the system to achieve 2π phase modulation at longer wavelengths without increasing the physical stroke length, thereby maintaining the same manufacturing precision requirements while improving wavelength adaptability.
Solution Approach 2:
The system changes the optical configuration parameter by introducing a mirror to double the light path through the modulation elements. This parameter change allows the same physical stroke to produce doubled phase modulation, enabling longer wavelength operation without requiring increased stroke precision.
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
This configuration improves the performance of MEMS-based SLMs by allowing operation at longer wavelengths with reduced stroke requirements, enhancing robustness and efficiency in LIDAR and other applications, while maintaining the ability for 2π phase operation.
Implementation Method 1
The modulation element is electrostatically actuated to deflect the reflective layer vertically through the gap
Implementation Method 2
The light is reflected off the mirror and back toward the modulation element
Implementation Method 3
The light reflected off the mirror is reflected by the modulation element out of the MEMS-based SLM
Data Source
AI summary
A micromechanical systems (MEMS)-based spatial light modulator (SLM) incorporates a mirror to increase the travel path of light. Light incoming to the MEMS-based SLM is incident on a modulation element of a phased-array. The modulation element reflects the light to a mirror, which reflects the light back to the modulation element. The modulation element reflects the light reflected off the mirror out of the MEMS-based SLM. A dispersive element allows the light to be steered by changing a wavelength of the light.