Asymmetric Six-Mirror Ring Resonator for Round Laser Beam Profile
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Solution Overview
Problem
Existing optical resonators with high Fresnel numbers, such as those used in high-energy laser systems, suffer from poor beam quality due to multimode operation and image rotation, resulting in a square beam profile that is suboptimal for both medical and military applications.
Innovation Solution
The optical resonator is designed with six mirrors arranged to achieve an image rotation angle that requires at least five revolutions to restore the original beam image orientation, promoting a rounder beam profile through phase synchronization and using a configuration where the first and fourth beam paths are parallel and variable in length, eliminating the need for a pentaprism and allowing for easier installation of optical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the image rotation angle is set to 90° per revolution (as in RISTRA resonator), then the beam quality is improved through phase synchronization, but the exit laser beam acquires a square profile that degrades beam quality
Solution Approach 1:
The patent applies asymmetry by deliberately choosing an image rotation angle that is NOT 90° (which would create 4-fold symmetry and square profile), but rather an angle that creates 5-fold or higher symmetry. This asymmetric choice relative to the conventional 90° rotation eliminates the square beam profile while maintaining phase synchronization benefits for beam quality.
2Device complexity
If six mirrors are used to form a ring resonator with 90° image rotation, then the device complexity is reduced compared to using a pentaprism, but the beam profile becomes square
Solution Approach 1:
The patent combines the six-mirror configuration with an asymmetric image rotation angle (not 90°) to achieve both device simplicity and round beam profile. The key is that the asymmetry in rotation angle, rather than in mirror count, is what prevents the square profile while maintaining the simplified six-mirror structure.
3Reliability
If the number of resonator revolutions is increased to at least five, then the beam profile becomes rounder and interference susceptibility is reduced, but the resonator length and complexity increase
Solution Approach 1:
The patent changes the critical parameter of image rotation angle to achieve the desired effect in fewer revolutions. By optimizing this angular parameter, the system achieves 5-fold or higher symmetry more efficiently, reducing the required resonator length while maintaining improved beam quality and reduced interference susceptibility.
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 significantly improves beam quality by achieving a high degree of symmetry and reducing interference susceptibility, resulting in a more robust and efficient laser beam profile that is closer to a round shape, enhancing the performance of high-power lasers and optical parametric oscillators.
Implementation Method 1
The mirrors are arranged in three different planes to produce, in use, an image rotation which is a rotation of the cross-sectional beam image of the laser beam
Implementation Method 2
at least five resonator revolutions are necessary until the original beam image orientation is essentially restored
Data Source
Figure 1a~1b
Figure 2a~4
Figure 5
AI summary
The optical resonator has several mirrors (M1-M6) that are arranged to form a ring structure. The two successive mirrors are connected to each other by the respective laser beam paths. The mirrors are arranged in two different planes to produce the image rotation which is a rotation of the cross-sectional pattern of laser beam. The mirrors are spatially arranged such that the image rotation is performed until the original beam image orientation is restored.