Field-programmable gate array-based residual amplitude modulation suppression and control for compact atomic clocks

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Optics
• Laser Physics

Background:

• Laser frequency stabilization is critical for high-precision measurements, particularly in optical atomic clocks.
• Residual Amplitude Modulation (RAM) is a significant noise source that degrades clock performance.
• Existing methods for RAM suppression can be complex and costly.

Purpose of the Study:

• To develop a cost-effective and integrated solution for laser frequency stabilization using FPGA technology.
• To implement an active residual amplitude modulation (RAM) suppression scheme.
• To improve the stability and performance of optical atomic clocks.

Main Methods:

• Designed a Field-Programmable Gate Array (FPGA) fabric for phase modulation laser locking.
• Incorporated an active residual amplitude modulation (RAM) suppression scheme utilizing complex modulation.
• Integrated all necessary servos for an optical atomic clock onto a single FPGA chip.

Main Results:

• Achieved reliable, long-term RAM suppression of 60 dB.
• Maintained residual RAM levels at -100 dBc.
• Demonstrated a three-decade improvement in stability when applied to a two-photon rubidium clock.

Conclusions:

• The developed FPGA fabric provides a comprehensive and integrated solution for laser frequency stabilization.
• The active RAM suppression scheme effectively mitigates a key noise source in optical clocks.
• This approach significantly enhances the stability of optical atomic clocks, paving the way for more precise timekeeping.