Phase-Transforming Optical Element via Partial Etching and Reflow
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Solution Overview
Problem
Current methods for producing optical elements with arbitrary phase transformation functions are limited by the complexity of grayscale or multilevel lithography techniques, making it difficult to implement continuous, arbitrary phase functions using binary lithographic techniques.
Innovation Solution
The development of optical elements with a transmissive layer comprising discrete volumes of two optical media, where the first medium is a solid reflowed material and the second medium can be vacuum, gaseous, or solid, arranged to impart a specified effective phase transformation function through partial etching and reflow, allowing for binary lithographic techniques to achieve an operationally acceptable approximation of the desired phase transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If grayscale or multilevel lithography techniques are used to produce optical elements with arbitrary phase transformation functions, then continuous phase functions can be achieved, but the fabrication process becomes complex and difficult to implement
Solution Approach 1:
The optical element is segmented into discrete volumes of two optical media arranged in a binary pattern. Instead of requiring continuous grayscale lithography, the phase transformation function is approximated by spatially distributing discrete high-index and low-index material volumes, effectively segmenting the continuous phase profile into discrete binary elements that can be fabricated using simpler binary lithographic techniques
Solution Approach 2:
The invention changes the fabrication parameter from continuous grayscale exposure to binary exposure followed by selective etching. By controlling the local thickness and material composition through binary patterning and selective removal of portions of the first optical medium, the phase transformation function is achieved without requiring complex multilevel lithography processes
2Ease of manufacture
If binary lithographic techniques are used to approximate continuous phase functions, then fabrication is simplified, but phase errors and unwanted diffraction or scattering increase
Solution Approach 1:
The invention applies local quality by varying the size, shape, and distribution of discrete material volumes throughout the optical element. Different regions contain different configurations of high-index and low-index material volumes, allowing each local region to contribute differently to the overall phase transformation while maintaining binary fabrication simplicity
Solution Approach 2:
The invention transitions from two-dimensional binary patterning to three-dimensional control by varying the local thickness of material layers. By controlling the thickness profile d(x,y) in the third dimension and combining it with binary in-plane patterning, the approach achieves continuous-like phase control while maintaining binary lithographic fabrication
3Ease of manufacture
If discrete volumes of optical media are arranged to impart phase transformation, then binary lithography can be used, but the morphology requires smoothing to reduce diffraction and scattering
Solution Approach 1:
The invention applies preliminary action by performing selective etching and reflow processes after binary lithographic patterning to smooth the morphology of discrete material volumes. The reflow process rounds sharp edges and corners of etched features before final optical coating, thereby reducing diffraction and scattering effects while preserving the binary-patterning-based phase transformation capability
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 enables the production of optical elements that effectively transmit or reflect optical signals with a specified phase transformation, achieving acceptable phase errors and reducing unwanted diffraction or scattering, while simplifying the fabrication process by using binary lithography and reflow to smooth out morphology.
Implementation Method 1
heating the transmissive layer to cause at least partial reflow of the first optical medium
Data Source
AI summary
An optical element includes a transmissive layer comprising a multitude of discrete volumes of first and second optical media arranged along the transmissive layer. The discrete volumes are arranged to approximate a desired phase function (typically modulo 2π) and are smaller than an operational wavelength in order to provide a range of phase delays needed to adequately approximate the desired phase function. Effecting at least partial reflow of one or both of the optical media can smooth the morphology of the transmissive layer so as to reduce unwanted diffraction or scattering.