Simultaneous two-photon resonant optical laser locking (STROLLing) in the hyperfine Paschen-Back regime

Area of Science:

• Atomic Physics
• Quantum Optics
• Laser Spectroscopy

Background:

• Precise control of atomic energy levels is essential for quantum technologies.
• Magnetic fields significantly alter atomic energy structures, complicating laser locking.
• Two-photon transitions offer advantages for probing atomic states but require sophisticated stabilization.

Purpose of the Study:

• To demonstrate a robust method for simultaneously locking two laser frequencies to a two-photon transition.
• To investigate the feasibility of this technique in the hyperfine Paschen-Back regime under a strong magnetic field.
• To assess the frequency stability of the locked lasers over extended periods.

Main Methods:

• Utilizing a ladder configuration involving 5S1/2, 5P3/2, and 5D5/2 terms in Rubidium-87 (Rb87) vapor.
• Applying a magnetic field strong enough to access the hyperfine Paschen-Back regime.
• Simultaneously locking two laser frequencies to the two-photon transition steps.

Main Results:

• The two-photon laser lock remained stable for over 24 hours.
• The frequency instability of the sum of the laser frequencies was measured to be less than the Rb D2 natural linewidth (6 MHz) across most timescales.
• Successful access to the hyperfine Paschen-Back regime was achieved.

Conclusions:

• The demonstrated technique provides a highly stable two-photon laser lock for Rb87 atoms in a strong magnetic field.
• This method offers a significant advancement for precision spectroscopy and quantum control applications.
• The achieved frequency stability is suitable for experiments requiring narrow linewidths.