Multilayer Substrate Vertical Step Micro Mirror
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Solution Overview
Problem
Conventional micro-optical elements with planar surfaces fail to achieve phase contrast effectively due to temperature-dependent planarity issues and mechanical stresses, leading to deteriorated imaging properties and potential delamination of coatings under short laser pulses.
Innovation Solution
Micro-optical elements with vertically stepped substrates featuring a symmetric nanolaminate structure, where an intermediate layer is confined between two substrate-forming layers, ensuring homogeneous reflectivity and thermal compensation to maintain planarity across the optically effective surface, using materials with matching thermal expansion coefficients and stress states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a coating is applied to the substrate to enhance reflectivity, then the optical performance is improved, but the planarity deteriorates due to layer stresses and thermal expansion differences
Solution Approach 1:
The patent applies different properties to different regions of the substrate. The coating layer is applied only to specific zones where high reflectivity is needed, while other zones remain uncoated or have different coatings. This local differentiation allows optimization of optical performance in critical areas without compromising overall planarity, as the coating stresses are confined to specific regions rather than uniformly distributing across the entire substrate.
Solution Approach 2:
The patent uses composite material structures, particularly in the multilayer substrate design with alternating layers of different materials (e.g., silicon nitride and silicon oxide). These composite layers have different mechanical and thermal properties that compensate for each other, reducing overall stress and maintaining planarity while providing the necessary optical reflectivity through the layered structure itself.
2Temperature
If the substrate temperature changes during operation, then the thermal effects are minimized, but mechanical stresses cause bending and planarity deterioration
Solution Approach 1:
The patent carefully selects materials with matching or complementary thermal expansion coefficients for the substrate layers and coating materials. By designing the multilayer structure with materials that have coordinated thermal properties, the patent minimizes differential thermal expansion during temperature changes, thereby reducing mechanical stresses that would otherwise cause bending and planarity deterioration.
Solution Approach 2:
The multilayer substrate uses composite material construction where alternating layers of different materials (e.g., silicon nitride and silicon oxide) provide balanced thermal and mechanical properties. This composite structure acts as a thermal compensation mechanism, where the different thermal expansion characteristics of individual layers cancel each other out, maintaining overall planarity despite temperature variations during laser processing.
3Adaptability or versatility
If vertical steps are introduced to achieve phase modulation, then the optical functionality is enhanced, but the mechanical strength and stiffness are reduced
Solution Approach 1:
The patent uses composite material layers with different mechanical properties to construct the vertical step structures. By combining materials with varying stiffness and strength characteristics in the multilayer configuration, the patent achieves the necessary phase modulation functionality through vertical steps while maintaining overall mechanical strength. The composite structure allows the steps to be optimized for optical function without compromising the substrate's structural integrity.
Solution Approach 2:
The vertical steps are introduced only in specific local regions where phase modulation is required, rather than throughout the entire substrate. This localized approach allows the optical functionality to be enhanced at critical areas while the rest of the substrate maintains its full mechanical strength and stiffness. The multilayer coating structure provides the necessary mechanical reinforcement at the step locations without compromising overall structural integrity.
4Ease of manufacture
If conventional planar micro-optical elements are used, then the manufacturing is simpler, but phase contrast techniques cannot be effectively achieved
Solution Approach 1:
The patent segments the substrate surface into different functional zones using vertical steps and multilayer structures. By dividing the optically effective surface into regions with different heights and optical properties, the patent enables phase contrast functionality while maintaining a relatively simple manufacturing process. The segmentation is achieved through standard lithographic and deposition techniques applied to create the multilayer vertical step structure.
Solution Approach 2:
The patent transitions from a two-dimensional planar surface to a three-dimensional structure with vertical steps and multilayer coatings. This dimensional change enables phase modulation capability by introducing height variations that create optical path differences. The multilayer structure adds another dimension of control through varying layer thicknesses and material compositions, enabling phase contrast functionality while maintaining manufacturability through established thin-film deposition 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
The solution ensures reproducible and homogeneous phase shifts with improved planarity and reduced mechanical stresses, enabling effective phase contrast techniques across the entire optically effective surface, even under varying temperature conditions and short laser pulses.
Implementation Method 1
using materials with matching thermal expansion coefficients and stress states
Implementation Method 2
A phase modulation of reflected or transmitted electromagnetic waves is possible
Implementation Method 3
grid-like interference structures
Implementation Method 4
They can be deflected, preferably electrostatically, around a rest position
Data Source
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AI summary
The invention relates to micro-optical elements having a substrate, to a method for manufacturing these elements and their use. The substrates have at least one vertical step at an optically effective surface. It is the object of the invention to provide micro-optical elements which have vertical steps at optically effective surfaces, observe a homogeneous reflectivity at both sides of the vertical step(s) and maintain a high planarity permanently and independently of the temperature. With micro-optical elements in accordance with the invention, vertical steps are formed in each case with an intermediate layer which is confined between at least two layers of a substrate.