Optimized Quasi-Optical Mode Converter for TE_33,12 in 210 GHz Gyrotron

Area of Science:

• Physics
• Electrical Engineering
• Optics

Background:

• High-performance mode converters are crucial for millimeter-wave applications.
• The TE33,12 mode conversion presents challenges due to specific geometric ratios.
• Existing methods often use fewer coupled modes for analysis.

Purpose of the Study:

• To design and analyze a high-performance quasi-optical mode converter for the TE33,12 mode at 210 GHz.
• To overcome the conversion challenge posed by a caustic-to-cavity radius ratio of approximately 0.41.
• To achieve high Gaussian mode content in the output.

Main Methods:

• Utilized an optimized dimpled wall launcher analyzed with coupling mode theory (25 coupled modes).
• Performed electromagnetic field analysis using MATLAB R2021b.
• Analyzed radiation fields using Gaussian optics and vector diffraction theory.
• Employed a quasi-elliptical mirror, elliptical mirror, and phase-corrected parabolic mirrors.

Main Results:

• Achieved 99.0% scalar Gaussian mode content.
• Achieved 97.4% vector Gaussian mode content after phase correction.
• The 25-coupled-mode analysis provided a more effective solution compared to the usual nine modes.

Conclusions:

• The designed quasi-optical mode converter effectively addresses the challenging TE33,12 mode conversion.
• The optimized dimpled wall launcher and advanced mirror system are key to the high performance.
• The results demonstrate a significant advancement in quasi-optical mode conversion technology.