CVD Single Crystal Diamond for Raman Lasers
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Solution Overview
Problem
Current CVD diamond materials for Raman lasers face challenges due to high defect densities, which lead to increased birefringence, absorption, and reduced thermal conductivity, limiting their performance and efficiency in optical applications.
Innovation Solution
A CVD single crystal diamond material with reduced point defect and dislocation densities, increased internal dimensions, and controlled nitrogen content is produced through a multi-stage growth process, optimizing growth conditions to minimize defects and enhance optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CVD diamond material is grown using conventional single-stage processes, then growth rate and productivity are improved, but defect density (point defects and dislocations) increases
Solution Approach 1:
The patent divides the diamond growth process into multiple stages with different nitrogen concentration conditions. The first stage uses higher nitrogen concentration (300-1000 ppb) to promote lateral growth and reduce dislocation density, while the second stage uses lower nitrogen concentration (<100 ppb) to reduce point defect density. This segmentation allows each stage to optimize for different quality parameters, resolving the contradiction between growth rate and defect density.
Solution Approach 2:
The first growth stage performs preliminary action by establishing a low dislocation density foundation before the second stage reduces point defects. The initial stage creates a crystal structure with minimized dislocations through controlled lateral growth, which then serves as the base for subsequent high-quality growth in the second stage with lower nitrogen concentration.
2Reliability
If nitrogen content is increased to control crystal defects, then dislocation density is reduced, but point defect density and absorption increase
Solution Approach 1:
The patent segments the nitrogen concentration control into two distinct phases: the first stage uses higher nitrogen (300-1000 ppb) to control dislocation formation, while the second stage uses lower nitrogen (<100 ppb) to minimize point defects and absorption. This temporal segmentation allows the material to benefit from both high and low nitrogen conditions without suffering their respective drawbacks simultaneously.
Solution Approach 2:
The growth process employs periodic action by alternating nitrogen concentration levels between stages. The nitrogen concentration is periodically adjusted from higher levels during the first stage to lower levels during the second stage, creating a rhythmic pattern of defect control that optimizes both dislocation and point defect management.
3Length of moving object
If internal dimension is increased for better optical performance, then Raman gain coefficient is improved, but defect density increases due to longer growth time
Solution Approach 1:
The patent segments the growth process into two stages where the first stage establishes a low dislocation density foundation that enables subsequent long-duration growth without excessive defect accumulation. The second stage then extends the internal dimension while maintaining low defect levels due to the optimized crystal structure created in the first stage.
Solution Approach 2:
The first growth stage performs preliminary action by creating a crystal structure with minimized dislocation density before the second stage extends the internal dimension. This preliminary optimization of the crystal structure enables longer growth times in the second stage without proportionally increasing defect density, thus allowing larger internal dimensions with maintained quality.
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 resulting diamond material exhibits low birefringence, absorption, and high thermal conductivity, reducing depolarization losses and increasing the Raman gain coefficient, thereby lowering the lasing threshold and improving the efficiency of Raman lasers.
Implementation Method 1
Chemical vapour deposition (CVD) is an established technique for depositing material onto a substrate. The technique has been extensively described in patent and other literature. For deposition of diamond, the CVD process typically involves providing a gas mixture that, on dissociation, can provide carbon and hydrogen.
Implementation Method 2
The dissociation of the source gas mixture is brought about by an energy source, such as microwaves, radio frequency energy, a flame, a hot filament or jet based technique. The reactive species are allowed to deposit onto a suitable substrate
Implementation Method 3
The reactive species are allowed to deposit onto a suitable substrate, typically held at between 700 °C and 1200 °C, to form diamond.
Data Source
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AI summary
Single crystal diamond material produced using chemical vapour deposition (CVD), and particularly diamond material having properties suitable for use in optical applications such as lasers, is disclosed. In particular, a CVD single crystal diamond material having preferred characteristics of longest linear internal dimension, birefringence and absorption coefficient, when measured at room temperature, is disclosed. Uses of the diamond material, including in a Raman laser, and methods of producing the diamond are also disclosed.