Bonded MEMS Mirror VCSEL for OCT Swept Source
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The monolithic formation of MEMS electrostatically actuated dielectric mirrors in MEMS tunable VCSELs leads to compatibility issues with the active region chemistry and risks of mirror snap-down due to overlap between the optical and electrostatic cavities, limiting tunability and stability.
Innovation Solution
A bonded MEMS mirror configuration is used, allowing for a separate electrostatic cavity outside the optical resonant cavity, enabling wider latitude in fabrication technologies and reducing the risk of mirror snap-down by pulling the mirror away from the active region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If MEMS mirror is monolithically formed over the active region, then device integration is improved, but chemistry compatibility issues arise and mirror snap-down risk increases
Solution Approach 1:
The device is divided into two separate components: the VCSEL active region and the MEMS mirror structure. The MEMS mirror is fabricated on a separate substrate and then bonded to the VCSEL, eliminating the overlap between optical and electrostatic cavities that causes snap-down issues while maintaining integration benefits
Solution Approach 2:
The MEMS mirror structure is extracted from the monolithic integration approach and placed on a separate substrate. This allows independent optimization of the electrostatic cavity geometry without being constrained by the optical cavity requirements, resolving the chemistry compatibility and snap-down risk issues
2Use of energy by moving object
If electrostatic cavity is made small to minimize drive voltage, then energy consumption is reduced, but optical cavity performance is compromised
Solution Approach 1:
The electrostatic cavity and optical cavity are segmented into separate structures on different substrates. This allows the electrostatic cavity to be independently optimized for minimal drive voltage without compromising optical cavity performance, as the two cavities no longer share the same space
Solution Approach 2:
A bonding substrate acts as an intermediary between the VCSEL active region and the MEMS mirror. This intermediary allows the electrostatic cavity to be positioned optimally for low drive voltage while maintaining the optical cavity's required dimensions and performance characteristics
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 enhances the tunability and stability of MEMS tunable VCSELs, improving high-speed frequency tuning and reducing the risk of damage, thereby supporting advanced imaging applications like OCT.
Implementation Method 1
An electrostatically actuated dielectric mirror is suspended over the active region and separated by an air gap that forms part of the electrostatic cavity for the dielectric mirror
Implementation Method 2
MEMS tunable vertical-cavity surface-emitting lasers (VCSELs) have been used in telecommunications applications
Implementation Method 3
a bonded gallium arsenide (GaAs)-based oxidized mirror
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A microelectromechanical systems (MEMS)-tunable vertical-cavity surfaceemitting laser (VCSEL) in which the MEMS mirror is a bonded to the active region. This allows for a separate electrostatic cavity, that is outside the laser's optical resonant cavity. Moreover, the use of this cavity configuration allows the MEMS mirror to be tuned by pulling the mirror away from the active region. This reduces the risk of snap down. Moreover, since the MEMS mirror is now bonded to the active region, much wider latitude is available in the technologies that are used to fabricate the MEMS mirror. This is preferably deployed as a swept source in an optical coherence tomography (OCT) system.