Coaxial Folded Laser Cavity for Compact High-Power Beam Quality
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Solution Overview
Problem
Existing gas laser cavities, particularly those excited by RF between coaxially arranged electrodes, face challenges in achieving compact configurations while maintaining high power output and beam quality, as the prior art slab-shape of these lasers makes it difficult to reduce size and efficiently confine the gaseous lasing medium.
Innovation Solution
A compact laser resonator cavity is designed with a folded optical resonator geometry using spherical mirrors and a channeled ceramic cylindrical element to confine the plasma discharge, allowing for a zig-zag beam path within a reduced volume, which reduces the RF power required and enhances beam quality and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a traditional slab-shape laser cavity is used, then the laser can accommodate the full width of the slab and maintain stable operation, but the laser size cannot be reduced and the mechanical structure becomes bulky
Solution Approach 1:
The patent transitions from a traditional slab-shaped cavity to a coaxial cylindrical geometry, utilizing the radial dimension between concentric electrodes to confine the plasma discharge. This dimensional change allows the laser medium to be confined in a compact cylindrical volume rather than requiring a large flat slab structure, thereby reducing overall laser size while maintaining stable operation
Solution Approach 2:
The patent employs a nested structure where the inner electrode is positioned within the outer electrode, creating a coaxial configuration. The plasma discharge is confined within the annular region between these nested electrodes, and the ceramic insert with channels is nested within this electrode structure. This nested arrangement maximizes space utilization and enables compact cavity design
2Power
If the plasma discharge volume is increased to achieve higher power output, then more power can be extracted, but the RF power required increases and beam quality deteriorates
Solution Approach 1:
The patent uses a ceramic insert with specifically designed channels that confine the plasma discharge to localized regions within the annular gap between electrodes. This creates non-uniform local conditions where the plasma is concentrated in specific channels rather than being distributed throughout a large volume, enabling high power output while maintaining good beam quality through controlled local plasma interactions
Solution Approach 2:
The patent optimizes parameters such as the channel dimensions, channel spacing, and ceramic insert geometry to control the plasma discharge characteristics. By adjusting these parameters, the system achieves the desired balance between power output and beam quality, allowing high power extraction without the harmful effects associated with large-volume discharges
3Temperature
If cooling channels are added to the electrode structure to improve thermal management, then thermal runout is reduced, but the mechanical complexity and number of components increase
Solution Approach 1:
The patent integrates the cooling channels directly into the electrode structure itself, merging the thermal management function with the electrical discharge function. The cooling channels are formed as part of the electrode body, eliminating the need for separate cooling systems and reducing overall mechanical complexity while effectively managing electrode temperature
Solution Approach 2:
The electrode structure serves multiple functions simultaneously: it provides the electrical discharge path for plasma generation, structurally supports the ceramic insert with channels, and incorporates cooling channels for thermal management. This multi-functional design reduces the number of separate components and simplifies the overall system while achieving effective temperature control
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 achieves a high power output of 60 Watts in a compact structure of 90 x 90 x 120 mm, with improved mechanical stability, thermal contact, and electrical contact, allowing for efficient operation and reduced RF power consumption.
Implementation Method 1
a folded optical resonator cavity defined by spherical mirrors having a radius of curvature and mounted at a distance apart which enables the generation of a multipass beam path between the mirrors
Implementation Method 2
The optical resonator cavity is confined in a gap between two cylindrical coaxial electrodes receiving RF power to excite a gas mixture, generating a plasma discharge under conditions that produce a population inversion in the gaseous lasing medium
Implementation Method 3
two cylindrical coaxial electrodes receiving RF power to excite a gas mixture
Implementation Method 4
within the annular shaped cross sectional gap between the two cylindrical electrodes, a channeled ceramic cylindrical element is used in order to confine the plasma discharge to within the channels only
Implementation Method 5
The folding angle between the incident and reflected beams at either of the mirrors, and the distance between the mirrors is calculated such that the path returns to its original starting point after an integral number of zig-zag trips
Data Source
Figure 1
Figure 2A
Figure 2B~2C
AI summary
A compact laser system with a folded annular resonator cavity defined by spherical mirrors, enabling the generation of a multipass beam path between the mirrors, each beam pass inclined at a small angle to the axis between the mirrors to form a zig-zag path therebetween. A long optical path is achieved within a short physical structure. This enables a good mode and high power output to be achieved in a short mechanical structure. The optical resonator cavity is confined in the gap between two cylindrical coaxial electrodes receiving RF power to excite the lasing gas. Apertures are provided in the main cavity mirrors, with a high reflectivity end mirror behind one aperture at one end and a partially reflective output coupler at the other end. A channeled ceramic cylindrical element within the annular shaped gap between the two cylindrical electrodes confines the lasing gas to the channels.