Compact, thermal-noise-limited reference cavity for ultra-low-noise microwave generation

Area of Science:

• Physics
• Optical Engineering
• Microwave Engineering

Background:

• Transportable photonic microwave generation systems require ultra-stable optical reference cavities.
• Existing cavities face limitations in thermal noise and sensitivity to external forces.
• Improving laser phase noise and frequency stability is critical for high-performance systems.

Purpose of the Study:

• To demonstrate an easy-to-manufacture, ultra-stable optical reference cavity.
• To enable high-performance photonic microwave generation in transportable systems.
• To achieve near thermal noise-limited performance at room temperature.

Main Methods:

• Designed a 25-mm-long ultra-stable optical reference cavity.
• Employed a rigid holding geometry insensitive to squeezing forces.
• Optimized cavity geometry to improve the thermal noise limit.

Main Results:

• Achieved laser phase noise near thermal noise limit for 1 Hz to 1 kHz offset.
• Supported 10 GHz generation with phase noise of -100 dBc/Hz at 1 Hz offset.
• Demonstrated fractional frequency stability of 2x10^-15 at 0.1 s averaging time.

Conclusions:

• The developed optical reference cavity is suitable for transportable photonic microwave generation.
• The design offers significant improvements in phase noise and frequency stability.
• This work contributes to the advancement of portable high-precision frequency standards.