Terahertz Lens Uneven Structure for Compact 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 uneven structure composed of recessed portions with varying height and width, aligned outer end portions, and a stepwise refractive index distribution, which reduces size and suppresses aberration, achieved through anisotropic etching and microloading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If SiO2 is used as an etching stopper layer to control etching depth, then the height of the uneven structure can be made uniform, but SiO2 absorbs terahertz waves and is not suitable for terahertz wave optical elements
Solution Approach 1:
The patent removes the SiO2 etching stopper layer from the structure because it absorbs terahertz waves. Instead, the etching process uses the substrate's own surface as the reference plane, and the uneven structure is formed directly on the substrate surface without requiring a separate stopper layer that would interfere with terahertz wave transmission.
Solution Approach 2:
The patent introduces a mask layer as an intermediary that serves dual purposes: it defines the pattern of the uneven structure during fabrication and also serves as the effective stopper for etching depth control. The mask layer is positioned on the substrate surface and allows precise control of etching depth without requiring SiO2 that would absorb terahertz waves.
2Ease of manufacture
If high-brightness processing lasers and interference masks are used to form uneven structures with spatially modulated height, then the uneven structure can be formed, but the process becomes complicated and requires multiple components
Solution Approach 1:
The patent removes the complex laser interference system and high-brightness processing lasers from the fabrication process. Instead, it uses conventional photolithography with a standard photomask to define the uneven structure pattern, followed by conventional etching processes, thereby dramatically simplifying the manufacturing system requirements.
Solution Approach 2:
The patent uses a photomask that copies the desired uneven structure pattern onto the substrate through photolithography. The mask layer is formed with the same pattern as the final uneven structure, allowing precise replication of the design without requiring complex real-time laser interference control.
3Manufacturing precision
If the height of the uneven structure is irregular to achieve phase modulation, then phase difference can be generated, but aberration is likely to occur
Solution Approach 1:
The patent applies different heights and widths of uneven structures in different regions of the substrate to achieve spatially varying phase modulation. Each local region has optimized dimensions (height and width) tailored to produce the specific phase shift required for that area, while the outer end portions are aligned to a common plane to prevent aberration.
Solution Approach 2:
The patent controls the etching depth uniformly across the substrate while varying the lateral dimensions (width) of the uneven structures in different regions to achieve phase modulation. By separating the control of depth (uniform) from width (variable), the patent achieves phase variation without height irregularity that would cause aberration.
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 enables a compact terahertz wave optical element with reduced aberration and simplified production, facilitating flexible phase distribution design and minimizing reflection at the interface with air without the need for additional reflection prevention 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, to form the uneven structure in the surface of the substrate
Implementation Method 3
the larger the width of the unevenness forming portion is, the higher the height of the unevenness forming portion may be. According to the configuration, since the microloading effect in etching is used
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.