Front Surface Stress Counteracting Layer for Optical Coatings

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Solution Overview

Problem

Thick optical coatings on mirrors and other devices often induce stress, leading to bending or warping, which is undesirable and can result in wavefront errors and poor optical quality, especially in systems like high-energy laser systems where precise reflection is required.

Innovation Solution

The implementation of a pre-stress layer that counteracts the stress induced by the optical coating layer, allowing for the fabrication of optical devices with desired shapes and reduced manufacturing costs and time, without the need for separate backside compensation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thick optical coatings are applied to mirrors or optical devices, then reflective performance and optical functionality are improved, but stress-induced bending and warping increase

Engineering Contradiction:

Improvereflective performanceVSAvoidbending and warping

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

A stress counteracting layer is applied to the front surface of the optical device before or with the optical coating. This layer generates preliminary stress that opposes and neutralizes the stress induced by the thick optical coating, preventing bending and warping of the substrate while maintaining the desired reflective performance

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The optical device is constructed as a composite structure consisting of the substrate, the stress counteracting layer made of different material properties, and the optical coating layer. This composite design allows the different layers to have complementary functions: the substrate provides structural support, the stress counteracting layer provides stress compensation, and the optical coating provides reflective functionality

Inventive Principle:

Principle #40Composite materials

2Reliability

If thick optical coatings are applied to mirrors or optical devices, then optical functionality is improved, but manufacturing complexity and additional processing steps increase

Engineering Contradiction:

Improveoptical functionalityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The stress counteracting layer and the optical coating layer are combined into a single multi-layer coating structure applied to the front surface of the optical device. This integration eliminates the need for separate backside compensation processes and reduces the number of manufacturing steps while achieving both stress compensation and optical functionality

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The stress compensation function is extracted from the traditional backside compensation approach and relocated to the front surface coating structure. This allows stress compensation to be achieved through the optical coating process itself, eliminating the need for separate compensation steps and simplifying the manufacturing process

Inventive Principle:

Principle #2Taking out (Extraction)

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 effectively mitigates coating stress, reducing wavefront errors and enabling the production of high-quality optical devices with improved bending resistance, suitable for use in high-energy laser systems and other applications requiring precise reflection.

Implementation Method 1

The first layer of material creates a first stress within the optical device that counteracts a second stress within the optical device created by the second layer of material

Methodology Applied

Scientific EffectStress:

Data Source

PatentUS11385383B2Coating stress mitigation through front surface coating manipulation on ultra-high reflectors or other optical devices

Publication Date: 2022.07.12 RAYTHEON CO

AI summary

An apparatus includes an optical device that includes a substrate, a first layer of material over the substrate, and a second layer of material comprising an optical coating over the first layer of material. The first layer of material creates a first stress within the optical device that counteracts a second stress within the optical device created by the second layer of material. The optical device may also include a third layer of material positioned between the substrate and the first layer of material. In some cases, the second layer of material creates a compressive stress within the optical device, and the first layer of material creates a tensile stress within the optical device that counteracts the compressive stress within the optical device.