Stabilizing the free spectral range of a large ring laser

Area of Science:

• Physics
• Geodesy
• Optical Engineering

Background:

• Ring lasers are essential for measuring rotation rates, with their perimeter directly influencing Sagnac frequency conversion.
• High perimeter stability (parts-per-billion level) is critical for large ring lasers used in geodesy and fundamental physics.

Purpose of the Study:

• To present two novel, complementary methods for actively controlling the perimeter length of large ring lasers.
• To achieve a relative length stability of 4 × 10^-10 in ring laser perimeters.
• To enhance the stability of heterolithic ring laser designs to match monolithic ones.

Main Methods:

• Active perimeter length control using phase detection between two longitudinal resonances and a local oscillator.
• Active perimeter length control utilizing a highly stable wavelength meter to measure absolute laser frequency.
• Implementation of complementary approaches for robust perimeter stabilization.

Main Results:

• Achieved a relative length stability of 4 × 10^-10 for the ring laser perimeter.
• Demonstrated the effectiveness of two distinct active control methods.
• Brought the stability of heterolithic ring laser designs comparable to monolithic designs.

Conclusions:

• The presented methods provide effective active control for ring laser perimeter length.
• These techniques significantly enhance the stability of large ring lasers for geodetic and physics applications.
• The developed approaches offer practical implementation for improving heterolithic laser performance.