Atomic frequency standard based on direct frequency comb spectroscopy.

Area of Science:

• Atomic Physics
• Quantum Optics
• Metrology

Background:

• Atomic frequency standards are crucial for precise timekeeping and scientific measurements.
• Traditional optical clocks often rely on complex continuous-wave (cw) laser systems.
• Two-photon transitions offer advantages for atomic clocks due to reduced sensitivity to external fields.

Purpose of the Study:

• To demonstrate a simplified atomic frequency standard architecture using frequency comb excitation.
• To compare the performance of a frequency comb-based standard with a conventional cw laser-based standard.
• To evaluate the feasibility of using frequency combs for two-photon transitions in atomic clocks.

Main Methods:

• Developed a high-performance atomic frequency standard utilizing Doppler-free direct frequency comb excitation.
• Targeted a two-photon transition in Rubidium-87 (⁸⁷Rb).
• Measured clock transition linewidth and ac-Stark shift using the frequency comb and compared with cw laser results.

Main Results:

• Achieved performance equivalent to a cw laser-based system.
• Demonstrated simplified optical clock architecture by eliminating the need for cw lasers.
• Measured linewidth and ac-Stark shift comparable to cw laser excitation at equal average power.
• Attained frequency instabilities down to 7.8(38) × 10^-15 at 2600 s, limited by temperature shifts.

Conclusions:

• Direct frequency comb excitation of two-photon transitions provides a simplified and high-performance alternative for atomic frequency standards.
• This approach significantly reduces the complexity of optical clock systems.
• Future improvements can be made by addressing temperature-dependent shifts for enhanced stability.