Diamond Optical Element with Out-Coupling Structure for Quantum Light Extraction
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Solution Overview
Problem
The production of high-quality single crystal diamond materials for quantum applications is hindered by weak single photon emission and limited light collection due to high refractive index, requiring innovative methods to enhance out-coupling of light while maintaining material purity and reducing decoherence times.
Innovation Solution
A multi-stage chemical vapour deposition process is employed, where a first layer with higher nitrogen concentration is grown for rapid lateral growth, followed by a second layer with lower nitrogen concentration to achieve high purity and large volume of quantum grade diamond, incorporating an out-coupling structure such as a diamond solid immersion lens to increase light collection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high purity single crystal diamond material is used as host for quantum spin defects, then long T2 times and stable optical transition frequencies are obtained, but single photon emission is very weak and light collection is limited due to high refractive index
Solution Approach 1:
The diamond structure is segmented into two functional layers: a first layer with higher nitrogen concentration (300 ppb to 5 ppm) that provides structural support and facilitates growth, and a second layer with lower nitrogen concentration (0.001 ppb to 250 ppb) that serves as the quantum-grade host material. This segmentation allows each layer to optimize its properties independently, resolving the contradiction between structural integrity and quantum performance.
Solution Approach 2:
The first layer acts as an intermediary between the substrate and the second quantum-grade layer. It provides a controlled environment for nitrogen incorporation that facilitates the growth of the ultra-pure second layer, while the out-coupling structure serves as an intermediary to enhance light extraction from the diamond to external collection optics, overcoming the high refractive index limitation.
2Quantity of substance
If multi-stage CVD process is used to grow diamond layers with different nitrogen concentrations, then large volume quantum grade diamond material is achieved, but manufacturing process complexity increases
Solution Approach 1:
The multi-stage CVD process maintains continuous useful action by growing the first layer with higher nitrogen concentration first, which then serves as the foundation for the second layer. Each stage builds upon the previous stage, with the first layer's nitrogen content facilitating the subsequent growth of the ultra-pure second layer, ensuring continuous production of quantum-grade material without interruption.
Solution Approach 2:
The manufacturing process utilizes parameter changes by systematically varying the nitrogen concentration in the gas phase between stages: the first stage uses higher nitrogen concentration (300 ppb to 5 ppm) to promote lateral growth and structural stability, while the second stage reduces nitrogen concentration (0.001 ppb to 250 ppb) to achieve ultra-pure quantum-grade material. This controlled parameter variation enables large volume production without excessive complexity.
3Productivity
If out-coupling structure is integrated to enhance light collection, then single photon collection efficiency is improved, but device structure and manufacturing become more complex
Solution Approach 1:
The out-coupling structure employs spheroidal or curved geometries (such as hemispherical lenses or domes) on the diamond surface. These curved surfaces reduce total internal reflection and improve light extraction efficiency compared to flat surfaces, thereby enhancing single photon collection without requiring complex internal optical components.
Solution Approach 2:
The out-coupling structure is merged with the diamond substrate itself, forming an integrated optical-diamond hybrid structure. Rather than adding separate external optical components, the diamond structure incorporates the out-coupling functionality directly, simplifying the overall device architecture while maintaining enhanced light collection performance.
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 allows for the production of larger, high-quality diamond optical elements with enhanced light out-coupling, significantly improving the collection efficiency of single photon emitters and extending decoherence times, thereby supporting advanced quantum information processing applications.
Implementation Method 1
growing a first layer of single crystal diamond material via a chemical vapour deposition technique using a gas phase having a first nitrogen concentration; growing a second layer of single crystal diamond material over said first layer via a chemical vapour deposition technique
Data Source
AI summary
A method of manufacturing an optical element, the method comprising: growing a first layer of single crystal diamond material via a chemical vapor deposition technique using a gas phase having a first nitrogen concentration; growing a second layer of single crystal diamond material over said first layer via a chemical vapor deposition technique using a gas phase having a second nitrogen concentration, wherein the second nitrogen concentration is lower than the first nitrogen concentration; forming an optical element from at least a portion of the second layer of single crystal diamond material; and forming an out-coupling structure at a surface of the optical element for increasing out-coupling of light.