Practical solution of a compact system with a higher-order mode for PDH laser frequency stabilization.

Area of Science:

• Optics and Photonics
• Laser Physics
• Cavity Quantum Electrodynamics

Background:

• Pound-Drever-Hall (PDH) technique is crucial for laser frequency stabilization.
• Compact ultrastable lasers are essential for space-based applications.
• Higher-order optical modes have potential for enhanced laser performance.

Purpose of the Study:

• To investigate the use of higher-order modes for PDH frequency stabilization in compact laser cavities.
• To evaluate the noise suppression and stability benefits of Hermite-Gaussian (HG) and Laguerre-Gaussian (LG) modes.
• To determine alignment tolerances for practical implementation.

Main Methods:

• Developed a spatial light modulation scheme to generate the HG33 mode.
• Utilized finite element analysis and numerical simulations to assess noise limits and stability.
• Analyzed the impact of optical alignment errors on the PDH error signal.

Main Results:

• The HG33 mode was generated with 56% theoretical efficiency.
• Symmetric HG and LG modes demonstrated superior performance over the fundamental mode in reducing thermal and intensity noise.
• The HG33 mode reduced the thermal noise limit by 33.0% (from 10.0 to 6.7 Hz/√Hz at 1 mHz).

Conclusions:

• Higher-order modes, particularly HG33, offer significant noise reduction and stability improvements for compact laser cavities.
• The proposed method provides a practical balance between performance and feasibility for space-deployable ultrastable lasers.
• Quantitative alignment tolerances were established to maintain mode purity and system performance.