Ultralow-noise photonic microwave synthesis using a soliton microcomb-based transfer oscillator

Area of Science:

• Photonics and Optical Engineering
• Microwave Engineering
• Quantum Metrology

Background:

• Ultralow-noise microwave generation is crucial for applications like timing, metrology, communications, and radio-astronomy.
• Current state-of-the-art relies on optical frequency division using mode-locked laser frequency combs, which often require high repetition rates and stringent stabilization.

Purpose of the Study:

• To demonstrate a novel method for generating ultralow-noise microwave signals using a microresonator-based Kerr frequency comb (soliton microcomb).
• To achieve phase noise levels competitive with or exceeding existing technologies.

Main Methods:

• Generation of a soliton microcomb with a 14 GHz repetition rate using an ultra-stable pump laser.
• Application of a transfer oscillator approach to derive a microwave reference signal.
• Cancellation of microcomb noise through electronic division and mixing.

Main Results:

• Achieved an absolute phase noise level below -60 dBc/Hz at 1 Hz offset frequency.
• Demonstrated phase noise of -135 dBc/Hz at 10 kHz offset frequency.
• Successfully derived an ultralow-noise microwave reference signal from the soliton microcomb.

Conclusions:

• The developed method using soliton microcombs offers a viable alternative for generating ultralow-noise microwave signals.
• Future integration with self-referenced microcombs and electro-optic combs holds potential for even more advanced signal generators.