Laser Oscillator Output Coupler Coating for Beam Quality
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Solution Overview
Problem
Existing laser oscillators face challenges in improving beam quality and suppressing scattered light, as they either complicate configurations with apertures that absorb laser beams or struggle to effectively coat surfaces to restrict high order mode oscillation.
Innovation Solution
A laser oscillator design featuring a discharge tube with an output coupler and rear mirror, where the output coupler's first surface is coated with a dielectric multilayer having a low reflectance at the center and a high reflectance around it, and the rear mirror's surface is coated with a high reflective coating at the center and a non-reflective coating around it, to suppress high order mode oscillation and enhance low order mode efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an aperture is arranged between the output coupler and rear mirror to limit the laser beam diameter, then high order mode oscillation is restrained and beam quality is improved, but the configuration becomes complicated and laser output deteriorates due to absorption
Solution Approach 1:
The patent extracts the beam diameter limiting function from a separate aperture component and integrates it into the output coupler coating structure. The concentric coating pattern on the output coupler surface itself performs the mode selection function that previously required a separate aperture, thereby simplifying the overall configuration while maintaining beam quality improvement.
Solution Approach 2:
The patent combines multiple functions into the output coupler: the reflective coating provides both the necessary optical reflection for laser oscillation and the concentric pattern structure that limits beam diameter. By merging the aperture's beam limiting function with the output coupler's reflective function, the patent eliminates the separate aperture component and reduces configuration complexity.
2Manufacturing precision
If an aperture is arranged to limit laser beam diameter, then high order mode oscillation is restrained, but the aperture absorbs laser beam and laser output deteriorates
Solution Approach 1:
The patent replaces the mechanical aperture system with an optical coating system. Instead of using a physical aperture that absorbs laser energy, the patent uses concentric reflective coatings on the output coupler that optically limit the beam diameter through reflectance variation. This substitution eliminates the energy absorption problem while maintaining the beam quality improvement.
Solution Approach 2:
The patent changes the reflectance parameter of the output coupler coating as a function of radial position. By creating a concentric pattern where reflectance varies with distance from the center, the patent achieves beam diameter control without energy absorption. The parameter change from uniform reflectance to radially-dependent reflectance enables mode selection while preserving laser output.
3Manufacturing precision
If a non-reflective film is coated at the peripheral portion of the output coupler to allow low order mode oscillation, then beam quality is improved, but scattered light generation is difficult to suppress
Solution Approach 1:
The patent applies different reflectance properties to different local regions of the output coupler surface. The concentric coating pattern creates zones with varying reflectance: the central region has one reflectance characteristic while the peripheral regions have different characteristics. This local quality variation enables both beam diameter control and scattered light suppression, as each region performs its specific function optimally.
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 improves beam quality by restricting high order mode oscillation, reduces scattered light, and maintains a simple, cost-effective setup without the need for apertures, thereby enhancing laser processing capabilities.
Implementation Method 1
A first coating material having first reflectance is stacked on a first area including a radial center portion of a surface of the output coupler, which faces the discharge area, and a second coating material having second reflectance higher than the first reflectance is stacked on a second area around the first area
Data Source
AI summary
A laser oscillator includes a discharge tube having a discharge area in which laser gas is excited and an output coupler and a rear mirror respectively arranged at both sides of the discharge tube. A first coating material having first reflectance is stacked as a dielectric multilayer on a first area including a radial center portion of a surface of the output coupler, which faces the discharge area, and a second coating material having second reflectance higher than the first reflectance is stacked as a dielectric multilayer on a second area around the first area.