Reflective Optics for Ellipsometry Polarization Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing beam focusing systems using reflective optics alter the angle of incidence of electromagnetic radiation on a sample surface, leading to undesirable changes in the polarization state, which are not easily accounted for in ellipsometry applications.
Innovation Solution
A reflective optics system comprising four mirrors, including convex and concave mirrors, where the planes of incidence are intentionally set to be non-orthogonal, allowing the input beam to maintain its angle of incidence while reducing polarization state effects, and a mathematical model with a rotation matrix is used to calibrate and compensate for these changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reflective optics with orthogonal planes of incidence are used to focus the beam, then the polarization state effects are minimized, but the angle of incidence on the sample surface is undesirably altered
Solution Approach 1:
The patent applies asymmetry by intentionally setting the planes of incidence to be non-orthogonal (at a specific angle θ rather than 90 degrees), and by using asymmetric mirror configurations (convex and concave mirrors with specific curvatures). This asymmetric arrangement allows the beam to maintain a constant angle of incidence on the sample while still achieving polarization state stability through the specific angular relationship between mirrors.
Solution Approach 2:
The patent changes the angular parameter from the conventional orthogonal (90 degrees) configuration to a specific non-orthogonal angle θ. This parameter change is implemented through the mathematical model that relates the mirror angles and curvatures to achieve both focused beam delivery and constant angle of incidence on the sample surface, thereby resolving the contradiction between polarization stability and angle control.
2Manufacturing precision
If the planes of incidence are set to be non-orthogonal to maintain angle of incidence, then the polarization state control is improved, but a mathematical calibration model is required to compensate for the changes
Solution Approach 1:
The patent applies preliminary action by developing and applying a mathematical calibration model before actual measurements. The model pre-calculates the relationship between the non-orthogonal mirror angles and the resulting beam parameters, allowing the system to compensate for polarization state changes in advance. This enables the use of non-orthogonal configurations while maintaining measurement accuracy through pre-computed correction factors.
3Productivity
If convex and concave mirrors are used for beam focusing, then the focused beam delivery is achieved, but the system complexity increases compared to simple refractive optics
Solution Approach 1:
The patent applies segmentation by dividing the focusing function into multiple discrete mirror elements (convex mirror, concave mirror, and additional flat mirrors) arranged in a specific sequence. Each mirror segment performs a specific function in the beam path (divergence, convergence, folding, focusing), allowing the complex focusing task to be distributed across simpler individual components rather than requiring a single complex lens system.
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 configuration minimizes the impact on the polarization state of the input beam, enabling focused beam delivery with reduced alterations to the angle of incidence, thus improving the precision and accuracy in ellipsometric measurements.
Implementation Method 1
an input beam (IB) of electromagnetic radiation having a specific polarization state is directed toward said first (M1) mirror and reflects from said reflective surface thereof
Implementation Method 2
said third (M3) and fourth (M4) mirrors providing convex and concave reflective surfaces, respectively
Data Source
AI summary
A method of applying a reflective optics system that requires the presence of both convex and a concave mirrors that have beam reflecting surfaces. Application thereof achieves focusing of a beam of electromagnetic radiation with reduced effects on a polarization state of an input beam state of polarization that results from adjustment of angles of incidence and reflections from the various mirrors involved.