Ultralow phase noise microwave generation with an Er:fiber-based optical frequency divider

Area of Science:

• Physics
• Optical Engineering
• Electrical Engineering

Background:

• High-performance microwave signal generation is crucial for advanced applications.
• Cryogenic microwave oscillators offer excellent phase noise but are bulky and expensive.
• Optical frequency division presents a promising alternative for high-fidelity microwave generation.

Purpose of the Study:

• To demonstrate an optical frequency divider for generating low-noise microwave signals.
• To evaluate the phase noise performance of the developed system.
• To compare the system's performance against state-of-the-art cryogenic oscillators.

Main Methods:

• Utilized a 200 MHz repetition rate Er:fiber mode-locked laser.
• Locked the laser to a stable optical frequency reference.
• Analyzed the phase noise contributions of the optical frequency divider.

Main Results:

• Generated microwave signals with phase noise comparable to or better than cryogenic oscillators.
• Achieved phase noise below -100 dBc/Hz at 1 Hz offset from a 10 GHz carrier.
• Demonstrated shot-noise-limited phase noise of -145 dBc/Hz for offset frequencies >10 kHz.

Conclusions:

• The Er:fiber optical frequency divider provides a high-performance, potentially more compact, alternative to cryogenic microwave oscillators.
• The system's phase noise is primarily limited by the optical reference at low offset frequencies and shot noise at higher offset frequencies.
• Further analysis of residual noise in the optical frequency divider can lead to enhanced performance.