Fabry-Perot Interferometer Gap Control via Intermediate Structure
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Solution Overview
Problem
Existing Fabry-Perot interferometers face limitations in achieving small, uniform gaps between mirrors due to electrode contact and glue shrinkage, leading to non-uniform gap widths and increased weight and manufacturing costs.
Innovation Solution
Incorporating an intermediate structure with recesses and protrusions to house the electrodes, preventing contact and bending, and using resilient glue to compensate for glue shrinkage, allowing for precise control of the gap width and maintaining mirror parallelism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the gap between mirrors is made very small, then the interferometer achieves better optical performance with narrower pass band, but the electrodes may easily touch each other causing device failure
Solution Approach 1:
The electrode pattern is extended from a simple planar design to include three-dimensional protrusions that extend toward the opposing electrode. This dimensional change allows the electrodes to occupy vertical space within the gap rather than only horizontal space, enabling smaller gap distances while preventing electrode contact through the protrusion geometry.
Solution Approach 2:
The mirror substrate is designed with non-uniform thickness, featuring thicker edge portions and a thinner central portion. This local quality variation allows the gap to be smaller in the central optical region while maintaining sufficient distance at the edges where electrodes are positioned, preventing electrode contact while achieving the desired small gap for optical performance.
2Stability of the object's composition
If mirrors are made thick to reduce bending from glue shrinkage, then the structural stability improves, but the weight and manufacturing costs increase
Solution Approach 1:
The mirror substrate employs non-uniform thickness distribution with thicker edges and thinner center. This local quality approach provides structural stability at the edges to resist glue shrinkage forces while minimizing material usage and weight in the central optical region where thinness is beneficial for optical performance.
Solution Approach 2:
The mirror substrate is functionally segmented into different regions: edge portions that provide structural support and resistance to bending forces from glue shrinkage, and a central portion that is thinner to reduce weight and improve optical transmission. This segmentation allows each region to optimize for its specific function.
3Reliability
If the gap between mirrors is increased to prevent electrode contact, then the reliability improves, but the optical performance deteriorates with wider pass band
Solution Approach 1:
The electrode design incorporates vertical protrusions that extend into the gap space, allowing the electrodes to be separated in the horizontal plane while maintaining electrical functionality. This enables the gap distance to be minimized for optimal optical performance without compromising electrode separation reliability, as the protrusions provide the necessary spacing in the critical horizontal dimension.
4Ease of manufacture
If non-uniform gap is accepted to simplify manufacturing, then the production cost decreases, but the functional wavelength band becomes wider and shifted
Solution Approach 1:
Protrusions are pre-formed on the mirror substrates before assembly. These protrusions serve as built-in mechanical guides and spacers that automatically ensure uniform gap formation during the assembly process, eliminating the need for complex post-assembly adjustments while maintaining high gap uniformity for optimal optical performance.
Solution Approach 2:
The protrusions create localized geometric features that enforce uniform spacing between mirrors across the entire aperture. This local geometric constraint propagates uniformity throughout the gap, ensuring consistent optical performance without requiring complex manufacturing processes.
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 the creation of Fabry-Perot interferometers with smaller, more uniform gaps, reducing the risk of electrode contact and bending, achieving a narrow pass band, and lowering manufacturing costs while maintaining linear actuator control.
Implementation Method 1
The interferometer comprises piezoelectric, electrostrictive or flexoelectric actuators
Implementation Method 2
The interferometer comprises piezoelectric, electrostrictive or flexoelectric actuators
Data Source
Figure 1~3
Figure 4a~4e
Figure 5a~5b
AI summary
The invention relates to a Fabry-Perot interferometer and a method for producing the same. More specifically, the invention relates to Fabry-Perot interferometers which are controllable with one or several actuators, such as piezoelectric, electrostrictive or flexoelectric actuators. In prior art technology there is a problem to achieve a sufficiently small and uniform gap between mirrors. In the present invention an intermediate structure (85a, 85b, 95a, 95b, 81a, 81b, 91a, 91b, 98a, 98b) is used between a mirror and an actuator or between two mirrors. The method of production also includes measuring the width distribution of the gap in several phases, and providing pre-actuation of actuators.