Mid-Infrared Refractive Optical Element Using Silicon Substrate
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Solution Overview
Problem
Current manufacturing methods for mid-infrared lenses are inefficient and costly due to the lack of suitable materials and techniques for producing lenses transparent in the 6-14 μm wavelength range, as silicon, despite being suitable for micro-optics, is not transparent enough in this range, and other materials like Ge, ZnSe, GaAs, and InP are expensive to process.
Innovation Solution
A refractive optical element design where a substrate with lower absorption coefficients than the lens material is used, allowing for the lens surface to be etched using established DRIE processes, providing optical power while the substrate contributes only to mechanical stability and thickness, enabling cost-efficient production of micro-lenses and retro-reflectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon is used as the substrate material for mid-infrared lenses, then manufacturing cost and ease of production are improved, but optical transmission in the 8-10 μm wavelength range deteriorates due to absorption bands
Solution Approach 1:
The optical element is segmented into multiple functional layers: a silicon substrate providing mechanical support and a separate lens layer (made of Ge, ZnSe, GaAs, or InP) providing optical functionality. This segmentation allows each layer to be optimized for its specific function - the substrate for cost-effective manufacturing and the lens layer for mid-infrared transmission.
Solution Approach 2:
The patent employs composite material structures where a silicon substrate is combined with a mid-infrared transparent lens material. The silicon substrate serves as a mechanically stable, cost-effective base, while the lens material layer (such as germanium, zinc selenide, gallium arsenide, or indium phosphide) provides the necessary optical transparency in the 6-14 μm wavelength range.
2Manufacturing precision
If diamond turning is used to manufacture mid-infrared lenses from materials like Ge, ZnSe, GaAs, or InP, then optical quality is improved, but manufacturing cost increases
Solution Approach 1:
The manufacturing process is segmented so that only the thin lens layer (not the entire optical element) requires precision diamond turning. The silicon substrate can be manufactured using cheaper, high-volume techniques, and only the small lens material layer needs precision machining to achieve the required optical surfaces.
Solution Approach 2:
High manufacturing precision is applied locally only where necessary - specifically to the lens surfaces of the thin lens material layer. The bulk silicon substrate can be produced with lower precision using cost-effective mass production techniques, since it serves primarily as a mechanical support structure rather than the primary optical element.
3Ease of manufacture
If cast molding is used to manufacture chalcogenide glass lenses, then manufacturing cost is reduced, but the ability to produce small lenses (<2mm) deteriorates
Solution Approach 1:
The patent uses thin film or thin layer technology where the lens functionality is achieved with a very thin layer of lens material deposited or bonded onto the silicon substrate. This thin-film approach enables the production of small-sized lenses (less than 2mm in diameter or thickness) that would be difficult or impossible to manufacture using traditional cast molding techniques for bulk chalcogenide glass.
4Manufacturing precision
If proportional DRIE etching is used to manufacture micro-optics, then manufacturing precision and scalability are improved, but applicability to non-silicon materials deteriorates
Solution Approach 1:
The optical element is divided into a silicon substrate (compatible with DRIE etching) and a separate lens material layer. The DRIE process is applied to the silicon substrate to create precise micro-optical structures, while the lens material layer is subsequently added to provide mid-infrared transmission. This segmentation allows the benefits of DRIE precision to be retained while overcoming its material limitations.
Solution Approach 2:
The silicon substrate acts as an intermediary that is compatible with both the DRIE manufacturing process and the subsequent addition of mid-infrared transparent lens materials. The silicon layer serves as a mediator that enables the use of highly precise DRIE etching techniques while ultimately supporting lens materials (Ge, ZnSe, GaAs, InP) that are not directly compatible with standard silicon DRIE processes.
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 cost-efficient, high-quality micro-optics with reduced absorption, enabling mass production of mid-infrared lenses and retro-reflectors with improved optical properties and mechanical stability, overcoming the limitations of existing materials and processes.
Implementation Method 1
a first layer arranged on the first side of the substrate, wherein the first layer comprises the first lens surface of the refractive optical element
Implementation Method 2
in a wavelength range from 6 μm to 15 μm, particularly from 8 μm to 10 μm, the substrate has a lower absorption coefficient than the first layer
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a refractive optical element (1) having an optical axis (OA), a first lens surface (11.1), wherein the refractive optical element (1) further comprises: a substrate (30) having a first side (31) and a second side (32) opposite the first side (31), a first layer (10) arranged on the first side (31) of the substrate (30), wherein the first layer (!0) forms the first lens surface (11.1) of the refractive optical element (1), wherein in a wavelength range from 6 µm to 15 µm, the substrate (30) has a lower absorption coefficient than the first layer (10).