Infrared GRIN Optical Elements via Layered Stack Fabrication

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Solution Overview

Problem

Current graded index optics are limited in infrared light transmission beyond a wavelength of two microns, as they are made from materials that either absorb infrared light or have slow and limited diffusion processes, restricting their complexity and efficiency for applications like sensing.

Innovation Solution

The method involves selecting infrared-transmitting materials with different refractive indices and similar thermo-viscous behavior, assembling them into a stack with a graded index profile, and shaping the stack into desired optical elements for infrared light transmission, such as plano-convex lenses or radially graded index optics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If traditional ion-doped silicate glasses or polymers are used for GRIN optics, then the manufacturing process is established, but infrared light transmission beyond two microns is blocked

Engineering Contradiction:

Improvemanufacturing processVSAvoidinfrared light transmission

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent uses composite materials by combining multiple infrared-transmitting materials with different refractive indices in a layered structure. This allows the creation of GRIN optics that transmit infrared light beyond two microns while achieving the desired graded index profile, overcoming the limitation of traditional single-material approaches that blocked IR transmission.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If ion exchange diffusion process is used to create index profile, then GRIN lens can be manufactured, but the process takes up to 200 hours for 2mm thick glass

Engineering Contradiction:

ImproveGRIN lens fabricationVSAvoidmanufacturing speed

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent applies preliminary action by pre-assembling the layered structure with the desired index profile before final forming. The layers are stacked in the correct configuration to create the graded index distribution, and then the entire stack is formed into the final lens shape in a single step, eliminating the need for slow diffusion processes.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If traditional microlayering/molding process is used, then plano-convex GRIN lenses can be fabricated, but the process is not applicable to IR materials

Engineering Contradiction:

Improvelens fabrication processVSAvoidapplicability to IR materials

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent changes the material parameters by selecting infrared-transmitting materials with appropriate refractive indices and similar thermo-viscous behavior. This parameter selection enables the application of layer stacking and forming processes to IR materials, making the fabrication method versatile for both visible and infrared optical applications.

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If polymer GRIN lenses are used, then manufacturing is simplified, but the index difference is limited to approximately 0.1

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidrefractive index difference

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent uses composite materials with different refractive indices to achieve a larger index difference than possible with single polymers. By combining multiple infrared-transmitting materials with varying refractive indices, the system achieves greater control over the index profile while maintaining manufacturing simplicity through the layer stacking approach.

Inventive Principle:

Principle #40Composite materials

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 enables the creation of efficient infrared-transmitting graded index optical elements that overcome previous limitations, allowing for effective beam focusing, coupling, and waveguiding in critical wavelength regions like mid-IR, while also being applicable to other wavelength ranges.

Implementation Method 1

assembling the infrared-transmitting materials into a stack comprising one or more layers of each infrared-transmitting material, resulting in the stack having a graded index profile

Methodology Applied

Scientific EffectGraded index profile:

Implementation Method 2

Graded index (GRIN) optics focus light through the use of an index profile in the lens instead of refracting the light of each surface

Methodology Applied

Scientific EffectGraded index focusing:

Data Source

PatentUS10689284B2Infrared (IR) transmitting graded index (GRIN) optical elements and method for making same

Publication Date: 2020.06.23 THE UNITED STATES OF AMERICA AS REPRESENTED BY THE SECRETARY OF THE NAVY

AI summary

The present invention is directed to a method for making infrared transmitting graded index optical elements by selecting at least two different infrared-transmitting materials, each with a different refractive index, having similar thermo-viscous behavior; assembling the infrared-transmitting materials into a stack comprising one or more layers of each infrared-transmitting material resulting in the stack having a graded index profile; and forming the stack into a desired shape. Also disclosed is the related optical element made by this method.