Coherent optical clock down-conversion for microwave frequencies with 10^-18 instability.

Area of Science:

• Metrology
• Atomic Physics
• Signal Processing

Background:

• Optical atomic clocks offer superior stability and accuracy over current microwave standards.
• Existing electronic systems, crucial for radar, navigation, and communications, are limited by less stable microwave sources.
• Bridging the performance gap between optical clocks and electronic domains is essential for technological advancement.

Purpose of the Study:

• To transfer the high performance of optical atomic clocks to the electronic domain.
• To generate a microwave signal that faithfully replicates the phase of an optical clock.
• To enable new applications in time dissemination, navigation, and interferometric imaging.

Main Methods:

• Comparing two independent optical-to-electronic signal generators.
• Utilizing advanced phase-tracking techniques.
• Characterizing the frequency instability of the generated microwave signal.

Main Results:

• Demonstrated a 10-gigahertz microwave signal with phase tracking the optical clock.
• Achieved an absolute fractional frequency instability of 1 × 10^-18 in the electronic domain.
• Confirmed faithful reproduction of the optical clock phase in the derived microwave signal.

Conclusions:

• The developed method successfully transfers optical clock performance to the electronic domain.
• This technology significantly enhances the potential of optical clocks for practical applications.
• Opens new avenues for precision time dissemination, enhanced navigation systems, and long-baseline interferometric imaging.