Stretchable Fresnel Zone Plate with Silicon Nanowires
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Fresnel zone plates have a fixed focal length, making them inflexible for applications requiring adjustable focusing, and integrating them with silicon-based electronic circuits is challenging due to high-temperature fabrication requirements of carbon nanotube forests.
Innovation Solution
A Fresnel zone plate design featuring radially spaced transparent and opaque rings with silicon nanowires, where a mechanically stretchable elastomer tuning structure adjusts the focal length by altering the radii of the rings, allowing for flexible integration with electronic circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon nanotube forests are used for opaque zones to achieve high contrast focusing, then optical absorption is improved, but fabrication temperature becomes extremely high making integration with silicon circuits difficult
Solution Approach 1:
The patent changes the material parameter from carbon nanotubes to silicon nanowires, which can be fabricated at lower temperatures compatible with silicon circuit processes. The silicon nanowires maintain the subwavelength spacing requirement for optical absorption while enabling integration with standard semiconductor manufacturing.
Solution Approach 2:
The patent uses a sacrificial oxide layer that is removed after serving its purpose as an etch stop and pattern transfer mask. This temporary structure enables the formation of silicon nanowires without requiring high-temperature carbon nanotube deposition, allowing standard silicon processing to be used.
2Ease of manufacture
If conventional Fresnel zone plate design is used, then manufacturing is simple, but focal length is fixed reducing flexibility
Solution Approach 1:
The patent makes the Fresnel zone plate dynamic by enabling electrostatic actuation of the membrane with patterned electrodes. This allows the focal length to be adjusted electrically without mechanical moving parts, maintaining manufacturing simplicity while adding adaptability for different focusing requirements.
Solution Approach 2:
The patent changes the physical state of the membrane from rigid to flexible, allowing it to be deformed by electrostatic forces. This enables continuous adjustment of the zone plate parameters (ring radii and spacing) to change the focal length, providing versatility while keeping the base structure simple to manufacture.
3Object-affected harmful factors
If high-temperature carbon nanotube fabrication is used, then optical absorption is achieved, but integration with silicon-based electronic circuits becomes difficult
Solution Approach 1:
The patent changes the fabrication temperature parameter from high (carbon nanotube deposition) to low (silicon nanowire formation via wet etching at room or moderate temperature). This allows the opaque zones to be formed using standard silicon processing techniques, enabling direct integration with silicon-based electronic circuits while maintaining effective light absorption through subwavelength silicon nanowire structures.
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
Enables adjustable focal length and simplified integration with electronic circuits, enhancing the flexibility and manufacturing ease of Fresnel zone plates for miniaturized optical systems.
Implementation Method 1
carbon nanotube forests exhibit near-perfect optical absorption due to low reflectance and nanoscale surface roughness
Implementation Method 2
a Fresnel zone plate includes a set of radially symmetric rings, known as Fresnel zones, which alternate between opaque and transparent. Incident light encountering the Fresnel zone plate will diffract around the opaque zones
Implementation Method 3
A plurality of silicon nanowires extend into at least one of the surfaces of the second set of rings. Each of the plurality of silicon nanowires is spaced from an adjacent one of the plurality of silicon nanowires by a distance. The distance is less than the wavelength of the incident light
Data Source
AI summary
A Fresnel zone plate is provided for encountering incident light having a wavelength. The Fresnel zone plate has a focal length and a wafer including alternating transparent and opaque zones, and a mourning surface. A plurality of silicon nanowires extend into opaque zone of the wafer. A mechanically stretchable tuning structure is mounted to the mounting surface such that stretching of the tuning structure varies the focal length of the Fresnel zone plate.