VCSEL Movable Mirror Beam Design for Electrostatic Deformation Control
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Solution Overview
Problem
The deformation of movable mirrors in tunable VCSELs due to electrostatic attractive forces leads to a decline in reflectance and increased lasing threshold, inhibiting the oscillation of surface emission lasers.
Innovation Solution
A surface emission laser design with a movable mirror connected by a second beam of shorter length, where both ends of the first beam are fixed, and the movable mirror is not electrically connected to the electrode, reducing deformation by minimizing the electrostatic influence and maintaining reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the HCG is pulled toward the active layer side by electrostatic attractive force, then the distance between the HCG and the active layer is reduced, but the shape of the HCG deforms to protrude toward the active layer side, causing reflectance decline
Solution Approach 1:
The patent divides the movable mirror structure into separate components: the HCG (high index contrast grating) and the beam structure. The HCG is positioned on the beam but not directly connected to the electrode, segmenting the electrostatic force application path and preventing direct deformation of the HCG by electrostatic forces.
Solution Approach 2:
The beam acts as an intermediary between the electrode and the HCG. The electrostatic force is applied to the beam rather than directly to the HCG, and the beam transmits this force mechanically to move the HCG. This intermediary structure prevents direct electrostatic deformation of the HCG while still achieving the desired movement.
2Length of moving object
If electrostatic attractive force is applied to the HCG, then the distance between the HCG and the active layer is reduced, but the lasing threshold increases due to shape deformation
Solution Approach 1:
The structure is segmented so that the HCG and the electrode actuation mechanism are separated. The HCG is not directly connected to the electrode, preventing direct electrostatic force application that would cause deformation and increase lasing threshold.
Solution Approach 2:
The beam serves as an intermediary that transmits mechanical force from the electrode to the HCG without applying electrostatic force directly to the HCG. This maintains the HCG's shape integrity while achieving the necessary position change to adjust the lasing wavelength.
3Adaptability or versatility
If the HCG is pulled toward the active layer, then the cavity length is varied for wavelength tuning, but the reflection direction changes and substantial reflectance declines
Solution Approach 1:
The HCG is segmented from the electrode actuation system, allowing independent optimization of each component. The HCG's geometry can be designed specifically for maintaining reflection direction, while the beam handles the actuation function.
Solution Approach 2:
The beam acts as an intermediary that provides controlled mechanical movement of the HCG without the electrostatic field distortion that would alter light reflection direction. This separation allows the HCG to maintain its optimal orientation for light reflection while still achieving wavelength tuning through position adjustment.
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 suppresses shape change of the movable mirror during operation, stabilizing the lasing threshold and ensuring consistent oscillation of the VCSEL.
Implementation Method 1
the HCG is pulled toward the side of an active layer by electrostatic attractive force
Data Source
AI summary
A surface emission laser includes a first beam, a second reflector disposed in an opening portion formed in the first beam, and a second beam disposed in the opening portion, and extending in a widthwise direction of the first beam to connect the second reflector and the first beam, wherein a length, in a longitudinal direction of the first beam, of the second beam is smaller than a length, in the longitudinal direction of the first beam, of the second reflector.