Ellipsometer Polarizer Intensity Control
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Solution Overview
Problem
Existing systems for measuring non-specular depolarizing samples, such as ellipsometers and polarimeters, face challenges in uniformly attenuating electromagnetic radiation intensity across wavelengths, leading to detector saturation and non-uniform results due to the limitations of neutral density filters and iris-based methods.
Innovation Solution
Incorporating a control polarizer and optionally a control compensator between the source and beam polarizer in an ellipsometer or polarimeter system, allowing for rotational adjustment to uniformly control the intensity of electromagnetic radiation across a spectrum, with the option of additional compensators for selective wavelength attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a neutral density filter is used to attenuate intensity, then detector saturation is prevented, but UV wavelengths are blocked and other wavelengths fall below detection threshold
Solution Approach 1:
The patent applies local quality by using a beam polarizer that differentially affects different wavelength components of the electromagnetic radiation. The polarizer selectively attenuates intensities across the spectrum based on polarization properties, allowing UV and other wavelengths to pass through while reducing intensity in the visible range, thus maintaining wavelength-specific transmission characteristics rather than uniform attenuation.
Solution Approach 2:
The patent employs parameter changes by rotating the beam polarizer to dynamically adjust the degree of intensity attenuation. By changing the orientation angle of the polarizer, the system can control the amount of intensity reduction across different wavelengths, enabling adaptation to various sample reflectivities and detector sensitivity requirements while maintaining broad wavelength transmission.
2Adaptability or versatility
If beam reflection off silicon substrate is used to emphasize IR and UV wavelengths, then wavelength selectivity is improved, but overall intensity reduction is not achieved
Solution Approach 1:
The patent merges two approaches: it combines the wavelength-selective reflection from the silicon substrate with the intensity-attenuating effect of the beam polarizer. This combination allows the system to simultaneously achieve both wavelength emphasis (IR and UV) and overall intensity reduction, solving the problem of detector saturation while maintaining spectral characteristics.
Solution Approach 2:
The system effectively creates a composite optical path that includes both the silicon substrate (providing wavelength-selective reflection) and the beam polarizer (providing intensity attenuation). This composite approach integrates the beneficial effects of both components to achieve simultaneous wavelength selectivity and intensity control.
3Illumination intensity
If an iris is used to reduce beam opening size, then overall intensity is reduced, but cross-sectional non-uniformity leads to non-uniform results
Solution Approach 1:
The patent replaces the mechanical iris (which physically blocks parts of the beam and creates non-uniformity) with an optical element (beam polarizer) that uniformly attenuates the beam through polarization effects. This substitution eliminates the mechanical cutting of the beam profile while achieving the desired intensity reduction, thereby maintaining beam uniformity across the cross-section.
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 uniform attenuation of electromagnetic radiation intensity across wavelengths, preventing detector saturation and ensuring consistent results for both reflective and less reflective samples, improving the measurement of depolarizing samples with low specular reflectance.
Implementation Method 1
the control polarizer is rotated with respect to the beam polarizer to substantially uniformly attenuate the intensity of all wavelengths which pass through said beam polarizer
Implementation Method 2
the beam polarizer sets a polarization state in said beam
Data Source
AI summary
An ellipsometer or polarimeter system and method for controlling intensity of an electromagnetic beam over a spectrum of wavelengths by applying control (P2) and beam (P) polarizers, optionally in combination with an intervening and control compensator (C).