Deterministic Nonlinear Transformations of Phase Noise in Quantum-Limited Frequency Combs.

Area of Science:

• Quantum optics
• Laser physics
• Nonlinear optics

Background:

• Femtosecond lasers are crucial for precision measurements.
• Understanding optical phase noise is vital for advanced applications.
• Nonlinear frequency conversion broadens laser spectra but can affect phase noise.

Purpose of the Study:

• To analyze optical phase noise evolution during nonlinear frequency conversion of femtosecond lasers.
• To identify the sources and behavior of phase noise across different conversion stages.
• To investigate the impact of phase locking on optical phase noise.

Main Methods:

• Analysis of optical phase noise in a femtosecond laser system.
• Utilizing supercontinuum generation via four-wave mixing.
• Employing difference frequency generation for passive phase locking.
• Extrapolating phase noise to radio frequencies.

Main Results:

• Intrinsic phase jitter originates from quantum statistics in the mode-locked oscillator.
• Supercontinuum generation shows a noise minimum at the carrier frequency.
• Comb linewidth quadratically increases with anticorrelated spectral wing fluctuations.
• Passive phase locking significantly enhances optical phase noise.

Conclusions:

• Optical phase noise transformation during nonlinear frequency conversion follows the elastic tape model.
• Phase locking elevates phase noise to the level of carrier-envelope phase jitter.
• The study provides insights into deterministic phase noise behavior in femtosecond laser systems.