Terahertz Lens Hole Array for Thin Low-Aberration Phase Control
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Solution Overview
Problem
Existing terahertz wave optical elements face challenges in minimizing size while avoiding aberration and complexity in production, particularly due to the use of SiO2 as an etching stopper layer, which absorbs terahertz waves, and the complexity of forming uneven structures using high brightness processing lasers and interference masks.
Innovation Solution
A terahertz wave optical element with a substrate featuring a periodic arrangement of recessed portions forming unevenness, where the height and width of these portions differ across regions, aligned to suppress aberration and reduce lens thickness, utilizing a method that includes anisotropic etching and microloading effects to facilitate precise phase difference generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If SiO2 is used as an etching stopper layer to achieve uniform etching depth, then the height of the uneven structure can be made uniform, but SiO2 absorbs light in the terahertz region making it unsuitable for terahertz wave optical elements
Solution Approach 1:
The patent removes the SiO2 etching stopper layer from the structure entirely. Instead, it uses a metal lens substrate with a reflective metal layer that serves both as the lens body and the etching stopper, eliminating the need for a separate SiO2 layer that absorbs terahertz waves.
Solution Approach 2:
The metal layer serves multiple functions: it acts as the reflective surface for terahertz wave optical processing, provides the etching stopper function during fabrication, and forms the structural base of the lens. This multi-functionality eliminates the need for separate SiO2 stopper layers.
2Ease of manufacture
If high brightness processing laser and interference mask are used to form uneven structure with spatially modulated height, then the uneven structure can be formed, but the process becomes complicated requiring multiple components
Solution Approach 1:
The patent replaces complex optical processing methods (laser interference and high brightness processing) with a simpler photolithography and etching process. The uneven structure is formed by patterning a metal layer using standard semiconductor fabrication techniques rather than complex laser-based methods.
3Manufacturing precision
If etching is stopped when etching stopper layer is exposed to achieve uniform height, then the height of uneven structure can be made uniform, but the position of outermost surface becomes irregular causing aberration
Solution Approach 1:
The patent applies different heights to different regions of the uneven structure according to their specific functional requirements. The metal lens substrate has a reflective metal layer with an uneven structure where the height varies by region, allowing each area to be optimized for its local optical function while maintaining overall aberration suppression through controlled height variation rather than uniform height.
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 effectively reduces lens size, suppresses aberration, and simplifies the production process by aligning outer end portions and using microloading effects to control etching, enabling flexible phase distribution design and reflection prevention without additional layers.
Implementation Method 1
a surface provided with an uneven structure that changes a phase of the terahertz wave
Implementation Method 2
performing anisotropic etching on the substrate in a state where the etching mask is formed on the surface of the substrate
Implementation Method 3
utilizing a method that includes anisotropic etching and microloading effects to facilitate precise phase difference generation
Data Source
AI summary
A terahertz wave lens includes a substrate having a surface provided with an uneven structure that changes a phase of the terahertz wave. The uneven structure includes a plurality of holes that are periodically arranged. The uneven structure includes a plurality of regions where the plurality of holes are arranged. A height of the hole in a thickness direction of the substrate and a width of the pillar differ for each of the regions. Outer end portions of the uneven structure in the thickness direction are located on the same plane.