Dual SOI Optical Deflector for Frequency Tuning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing two-dimensional optical deflectors face limitations in frequency adjustment and surface quality due to constraints in thickness of piezoelectric actuators, leading to suboptimal performance and potential damage to the active layer during PZT deposition and etching.
Innovation Solution
The design employs a dual SOI structure with varying active layer heights to independently control the frequencies of inner and outer piezoelectric actuators, while keeping the mirror separate from the active layer to prevent surface damage, allowing for improved frequency adjustment and mirror quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the outer piezoelectric actuators is decreased to lower their frequency, then the frequency of outer piezoelectric actuators is reduced, but the thickness cannot be decreased while maintaining the thickness of the mirror, torsion bars and inner piezoelectric actuators
Solution Approach 1:
The patent divides the SOI structure into two separate structures: a first SOI structure for the inner piezoelectric actuators and a second SOI structure for the outer piezoelectric actuators and mirror. This segmentation allows independent thickness control for each component, enabling the outer piezoelectric actuators to have different thickness than the mirror and torsion bars, thus resolving the contradiction in frequency adjustment.
Solution Approach 2:
The patent applies different active layer heights to different parts of the device: the first monocrystalline silicon active layer has a first height for inner piezoelectric actuators, while the second monocrystalline silicon active layer has a second height for outer piezoelectric actuators and mirror. This local quality differentiation allows each component to have optimized thickness for its specific function, enabling independent frequency control.
2Speed
If the thickness of the inner piezoelectric actuators is increased to raise their frequency, then the frequency of inner piezoelectric actuators is increased, but the thickness cannot be increased while maintaining the thickness of the outer piezoelectric actuators
Solution Approach 1:
By segmenting the SOI structure into two separate structures, the patent enables independent thickness optimization for inner and outer piezoelectric actuators. The first SOI structure can have a different active layer height than the second SOI structure, allowing the inner piezoelectric actuators to have increased thickness for higher frequency without constraining the outer piezoelectric actuators.
Solution Approach 2:
The patent implements different active layer heights locally: the first monocrystalline silicon active layer has a first height optimized for inner piezoelectric actuators, while the second monocrystalline silicon active layer has a second height for outer piezoelectric actuators. This local differentiation allows independent frequency optimization for each actuator type.
3Ease of manufacture
If PZT layer is deposited and patterned on the active layer, then the piezoelectric actuators are formed, but the surface of the active layer is damaged and residual stresses are generated
Solution Approach 1:
The patent extracts the PZT layer deposition process from the mirror fabrication sequence. By forming the PZT layer and patterning it before mirror deposition, and by using a separate second SOI structure for the mirror, the process eliminates damage to the active layer surface while still achieving the required piezoelectric actuator functionality.
Solution Approach 2:
The patent performs the PZT layer deposition and patterning as a preliminary action before mirror formation. The PZT layer is deposited on the first monocrystalline silicon active layer, patterned, and then the mirror is formed on the second monocrystalline silicon active layer. This preliminary action sequence prevents surface damage to the final mirror surface while still achieving the piezoelectric actuators.
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 approach enables flexible frequency tuning and enhances the mirror's quality by decoupling the piezoelectric actuators' thickness from the mirror's surface, reducing residual stresses and maintaining the active layer's integrity.
Implementation Method 1
inner piezoelectric actuators coupled between the torsion bars and supported by the inner frame via inner coupling portions, serving as cantilevers for rocking the mirror with respect to the X-axis of the mirror
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A two-dimensional optical deflector includes a first S0I structure (S1) and a second S0I structure (S2). A height (h1) of a monocrystalline silicon support layer (101) of the first S0I structure (S1) is smaller than a height (h3) of a monocrystalline silicon support layer (201) of the second S0I structure (S2). A mirror (1) includes a monocrystalline silicon active layer (203) of the first S0I structure (S1). An inner frame (3), an inner piezoelectric actuator (4a, 4b; 14a, 14b) and an outer frame (5) include a monocrystalline silicon active layer (103) of the first S0I structure (S1) and the monocrystalline silicon active layer (203) of the second S0I structure (S2). An outer piezoelectric actuator (6a, 6b) includes the monocrystalline silicon active layer (103) of the first S0I structure (S1).