Ultra-Broadband Absorber Using Gradient Refractive Index Coating
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Solution Overview
Problem
Existing visible near-infrared broadband absorbers are complex, time-consuming, and costly to produce, making them unsuitable for large-scale mass production, and they often have inadequate absorption performance and sensitivity to incidence angles.
Innovation Solution
A visible near-infrared ultra-broadband absorber is designed with a substrate, a bottom metal absorbing layer, a top germanium layer, and a three-layer broadband anti-reflection coating with gradually decreasing refractive indexes, fabricated using vacuum coating to simplify the production process and enhance absorption efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex multilayer structures with many metal and medium layers are used to achieve broadband absorption, then absorption performance is improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent extracts and eliminates unnecessary intermediate layers from complex multilayer structures. By removing redundant metal and dielectric layers while retaining only the essential bottom metal absorbing layer and top germanium layer, the design achieves broadband absorption with a simplified structure that is easier to manufacture and less costly.
Solution Approach 2:
The patent employs composite material strategy by combining specific materials (germanium, metal layers, and anti-reflection coating materials with gradually decreasing refractive indexes) in a optimized configuration. This composite approach enables the simplified structure to achieve absorption performance comparable to or exceeding complex multilayer designs.
2Reliability
If conventional vapor deposition and liquid deposition methods are used to prepare absorber structures, then absorption performance can be achieved, but production time and cost increase
Solution Approach 1:
The patent replaces complex chemical deposition processes (vapor deposition and liquid deposition) with a simplified vacuum coating process. This substitution maintains the required absorption performance while dramatically reducing production time and manufacturing complexity, enabling large-scale mass production.
Solution Approach 2:
The patent optimizes critical parameters including the refractive indexes of anti-reflection coating layers (gradually decreasing from bottom to top), layer thicknesses (bottom metal layer ≥100 nm, top germanium layer 10-40 nm), and material compositions. These parameter optimizations enable the simplified structure to achieve superior absorption performance with faster, more cost-effective vacuum coating fabrication.
3Reliability
If absorber structures with specific layer configurations are designed to achieve broadband absorption, then absorption bandwidth is improved, but sensitivity to incidence angle increases
Solution Approach 1:
The patent applies local quality principle by designing the anti-reflection coating with a specific gradient structure where each layer has a progressively decreasing refractive index from bottom to top. This localized optimization of refractive index distribution enhances both broadband absorption and incidence angle insensitivity by controlling light reflection and transmission at different angles across the absorption band.
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 solution achieves wider absorption bands, better absorption performance, and improved incidence angle insensitivity, reducing production costs and complexity, making it suitable for large-scale production and applications in photo-thermal conversion, electromagnetic absorption, and imaging.
Implementation Method 1
a three-layer broadband anti-reflection coating respectively comprises a bottom layer, an intermediate layer and an outmost layer on the top germanium layer in proper sequence with gradually decreasing refractive indexes
Implementation Method 2
gradually decreasing refractive indexes
Implementation Method 3
a bottom metal absorbing layer, a top germanium layer and a three-layer broadband anti-reflection coating are provided in proper order on the substrate
Implementation Method 4
fabricated using vacuum coating to simplify the production process and enhance absorption efficiency
Data Source
AI summary
The present invention discloses a visible near-infrared ultra-broadband absorber and its preparation method, comprising a substrate and a five-layer optical film, wherein the bottom film is a bottom metal absorbing layer; a top germanium layer is provided on the top of the bottom metal absorbing layer; and remaining three layers are provided on the top of the top germanium layer with gradually decreasing refractive indexes from the bottom to the top. The present invention is based on the blocking effect of the metal absorbing layer and broadband anti-reflection film stack of the germanium layer, which has realized visible near-infrared ultra-broadband absorption with high efficiency and good angle insensitivity, and has fully surpassed traditional absorbers in terms of performances. Compared with conventional broadband absorbers and artificial electromagnetic absorbers proposed in recent years, the compact multilayer film structure in the present invention is simpler and avoids complicated nano-fabrication techniques. Therefore, it can significantly reduce production cost and shorten the production cycle, and is thus suitable for large-scale mass production.