Achromatic Rotating-Element Ellipsometer Mueller Matrix Measurement
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Solution Overview
Problem
Existing optical element rotation type ellipsometers cannot measure Mueller-matrix elements of anisotropic samples effectively, requiring additional measurements like rotating the sample or scanning fixed optical elements, which complicates the detection of shape and physical properties.
Innovation Solution
An achromatic rotating-element ellipsometer is designed with a light source, fixed and constant speed rotation polarizers and analyzers, and a photodetector to measure the Mueller-matrix components by calculating Fourier coefficients from the radiant flux waveform, allowing for the measurement of both anisotropic and isotropic samples using four polarizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional measurements such as rotating the direction of the sample or scanning the fixed optical element are performed, then Mueller-matrix elements of anisotropic samples can be measured, but the measurement time and device complexity increase
Solution Approach 1:
The patent employs dynamic rotation of optical elements (polarizer and analyzer) at constant speeds to enable simultaneous measurement of all Mueller-matrix elements. By rotating the polarizer at angular velocity ω1 and the analyzer at angular velocity ω2, the system captures complete polarization state information in a single measurement sequence, eliminating the need for multiple static measurements or sample reorientations.
Solution Approach 2:
The measurement system utilizes periodic rotation of optical elements to modulate the polarization state of light passing through the sample. The polarizer and analyzer rotate periodically at constant speeds, creating time-varying polarization conditions that encode all Mueller-matrix elements into the temporal signal, which can then be extracted through Fourier analysis.
2Measurement precision
If additional measurements such as rotating the direction of the sample or scanning the fixed optical element are performed, then Mueller-matrix elements of anisotropic samples can be measured, but the device complexity increases
Solution Approach 1:
The patent employs dynamic rotation of optical elements (polarizer and analyzer) at constant speeds to enable simultaneous measurement of all Mueller-matrix elements. By rotating the polarizer at angular velocity ω1 and the analyzer at angular velocity ω2, the system captures complete polarization state information in a single measurement sequence, eliminating the need for multiple static measurements or sample reorientations.
Solution Approach 2:
The patent replaces complex mechanical sample manipulation systems with a simpler optical element rotation mechanism. Instead of requiring sample rotation stages or multiple fixed optical elements, the system uses two rotating polarizers/analyzers whose rotation speeds can be controlled electronically, reducing mechanical complexity while achieving the same measurement capability.
3Ease of manufacture
If three polarizers are used to find Fourier coefficients, then the basic measurement function is achieved, but the ability to measure anisotropic samples is insufficient
Solution Approach 1:
The patent creates a universal measurement system that can handle both isotropic and anisotropic samples using the same optical configuration. By implementing dual rotation of polarizer and analyzer, the system becomes multi-functional, capable of measuring all 16 Mueller-matrix elements regardless of sample symmetry, thus achieving universality without requiring additional specialized components for different sample types.
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 quick and accurate measurement of the shape and physical properties of anisotropic samples, improving upon existing methods by directly calculating Mueller-matrix elements without the need for additional measurements.
Implementation Method 1
a fixed polarizer configured to be disposed between the light source and the sample on a travel path of the incident light and polarize the incident light radiated from the light source
Implementation Method 2
a constant speed rotation polarizer configured to be disposed between the fixed polarizer and the sample on the travel path of the incident light, have the light passing through the fixed polarizer be incident thereon, and rotate at a constant speed for polarizing the incident light
Implementation Method 3
a constant speed rotation analyzer configured to have the light polarized by passing through the constant speed rotation polarizer incident thereon and rotate at a constant speed for polarizing the incident light, with the polarization state of the light polarized by passing through the constant speed rotation polarizer being changed by being reflected from or transmitted through the sample
Implementation Method 4
a fixed analyzer configured to have the light polarized by passing through the constant speed rotation analyzer incident thereon and polarize the incident light
Implementation Method 5
a photodetector configured to have the light polarized by passing through the fixed analyzer incident thereon, detect an exposure of the incident light, and output a value of a radiant flux of light corresponding to the exposure
Data Source
AI summary
The present invention relates to an optical element rotation type ellipsometer, and more particularly, to an ellipsometer used to measure Mueller-matrix components of a sample by measuring and analyzing a change in a polarization state of light reflected or transmitted by the sample.According to the exemplary embodiment of the present invention, it is possible to provide the achromatic rotating-element ellipsometer and the method for measuring Mueller-matrix elements of a sample using the same capable of measuring the Mueller-matrix elements of the anisotropic sample as well as the isotropic sample by using four polarizers.