GRIN Lens Sol-Gel Preform Phase Separation Prevention
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Solution Overview
Problem
Conventional sol-gel processes for manufacturing GRIN lenses face issues such as preform breaking and phase separation during sintering, low viscosity during wire-drawing, and low yield, especially with high dopant concentrations, due to the dissolution of aluminum and phase separation.
Innovation Solution
A method involving the formation of a wet gel with silicon alkoxide, aluminum alkoxide, and dopant alkoxide, where aluminum is added in a specific order to prevent dissolution during leaching, ensuring a sufficient concentration of aluminum remains in the glass preform, thereby increasing viscosity and suppressing phase separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dopant concentration is increased to achieve high numerical aperture, then optical performance is improved, but preform breaking and phase separation occur during sintering
Solution Approach 1:
The patent changes the chemical composition parameters of the glass preform by adding aluminum oxide as a third component alongside silicon dioxide and dopant oxide. This compositional modification alters the sintering behavior and phase stability of the glass system, enabling high dopant concentrations (10-20 mole percent) to be sintered without breaking or phase separation, thus achieving high numerical aperture while maintaining preform stability
Solution Approach 2:
The patent creates a composite glass system with three main components: silicon dioxide (base glass), dopant oxide (for refractive index control), and aluminum oxide (as a stabilizing third component). This composite material structure prevents the harmful effects of high dopant concentration during sintering while maintaining the desired optical properties, resolving the contradiction between high numerical aperture and preform stability
2Illumination intensity
If dopant concentration is increased to achieve high numerical aperture, then optical performance is improved, but marked phase separation occurs during sintering
Solution Approach 1:
The patent modifies the compositional parameters by incorporating aluminum oxide into the glass system. This parameter change suppresses the phase separation tendency that occurs with high dopant concentrations, maintaining compositional uniformity during sintering while still achieving the desired high numerical aperture through increased dopant content
Solution Approach 2:
The addition of aluminum oxide as a third component creates a composite glass system that is more resistant to phase separation. The aluminum oxide acts as a stabilizing phase that prevents the dopant from separating out during sintering, thus maintaining compositional stability even at high dopant concentrations required for high numerical aperture
3Reliability
If aluminum alkoxide is added to wet gel, then aluminum concentration increases to prevent breaking, but aluminum is dissolved away by acid during leaching
Solution Approach 1:
The patent applies preliminary action by adding aluminum alkoxide to the wet gel before the leaching process. The aluminum is incorporated into the gel structure in advance, where it can then protect against breaking during subsequent sintering. The timing of addition is critical - it must be added early enough to be incorporated into the gel network but the process is designed so that not all aluminum is leached away, retaining sufficient amounts for structural stability
Solution Approach 2:
The patent optimizes the concentration parameter of aluminum alkoxide added to the wet gel. By carefully controlling the amount of aluminum alkoxide added (specific mole percentages relative to silicon alkoxide), the patent achieves a balance where sufficient aluminum remains after leaching to prevent breaking during sintering, while acknowledging that some aluminum loss during leaching is inevitable. This parameter optimization resolves the contradiction between gaining preform strength and minimizing aluminum loss
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 method enhances the yield and transparency of GRIN lenses by preventing breaking and phase separation, facilitating stable wire-drawing and achieving high numerical aperture with high dopant concentrations, resulting in a colorless and transparent product with improved light transmission.
Implementation Method 1
hydrolysis is performed to form a sol
Implementation Method 2
the sol is further subjected to polycondensation
Implementation Method 3
The resulting wet gel is dried, the solvent in the gel is removed
Implementation Method 4
firing is performed to produce a cylindrical, dense glass preform provided with a refractive index distribution
Implementation Method 5
In the leaching, a wet gel is immersed in an acid solution, and the dopant in the peripheral portion is dissolved away
Data Source
AI summary
[Object] In the manufacture of a GRIN lens using a sol-gel process, breaking and phase separation of a preform are prevented and the viscosity during wire-drawing is increased so that the yield is improved, and also production of a GRIN lens with a high numerical aperture is enabled. [Solving Means] In the manufacture of a GRIN lens using a sol-gel process, in the process of forming a wet gel from an alcohol solution containing, as main components, a silicon alkoxide, a dopant alkoxide, and an aluminum alkoxide, first, an alcohol solution containing the silicon alkoxide and the aluminum alkoxide as main components is prepared, and then the dopant alkoxide is mixed thereto.