Fiber laser frequency stabilization at 780 nm via second-harmonic generation and modulation transfer spectroscopy...

Area of Science:

• Atomic, Molecular, and Optical Physics
• Laser Physics and Photonics
• Metrology and Measurement Science

Background:

• Precise laser frequency control is essential for applications like atomic clocks, quantum computing, and high-resolution spectroscopy.
• Existing frequency stabilization systems face challenges in achieving both high short-term and long-term stability due to noise and bandwidth limitations.

Purpose of the Study:

• To demonstrate a high-performance frequency stabilization system for the 87Rb D2 line.
• To achieve unprecedented frequency stability by optimizing spectroscopic parameters and noise suppression techniques.
• To assess and mitigate noise sources using the intensity-noise-equivalent laser power (INELP) concept.

Main Methods:

• Utilized a 1560 nm fiber laser frequency-doubled to 780 nm, locked to the 87Rb D2 line using modulation transfer spectroscopy.
• Optimized spectroscopic parameters and implemented advanced noise suppression techniques.
• Introduced the intensity-noise-equivalent laser power (INELP) concept for accurate in-loop noise assessment.
• Employed active power stabilization with a fiber-coupled acousto-optic modulator (AOM).

Main Results:

• Achieved a short-term stability of 3.32 × 10^-13 / τ.
• Reached a stability of 2.8 × 10^-13 at 20 s integration time with active power stabilization.
• Maintained stability below 4 × 10^-12 even at 10^4 s integration time.
• Identified piezoelectric actuator resonance (∼20 kHz) as the primary limitation for servo bandwidth.

Conclusions:

• The developed system offers high-performance frequency stabilization for the 87Rb D2 line.
• The INELP concept provides accurate in-loop noise assessment, crucial for stability optimization.
• Future improvements in short-term stability are expected by implementing a faster feedback loop using an AOM to overcome current servo bandwidth limitations.