Rydberg electromagnetically induced transparency based laser lock to Zeeman sublevels with 0.6 GHz scanning range

TL;DR

This paper introduces a method to lock a laser to Zeeman-split Rydberg transitions in rubidium, enabling continuous tuning over 0.6 GHz with high stability, beneficial for Rydberg atom research.

Contribution

A novel laser locking technique to Zeeman sublevels of Rydberg states allowing 0.6 GHz tuning range with improved stability and reduced polarization-dependent shifts.

Findings

Achieved 0.15 MHz short-term and 0.5 MHz long-term stability.

Demonstrated 0.8 MHz linewidth with magnetic field, 1.8 MHz without.

Reduced polarization-induced frequency shift from 1.6 MHz to 0.6 MHz.

Abstract

We propose a technique for frequency locking a laser to the Zeeman sublevel transitions between the 5P$_{3/2}$ intermediate and 32D$_{5/2}$ Rydberg states in $^{87}$Rb. This method allows for continuous frequency tuning over 0.6 GHz by varying an applied external magnetic field. In the presence of the applied field, the electromagnetically induced transparency (EIT) spectrum of an atomic vapor splits via the Zeeman effect according to the strength of the magnetic field and the polarization of the pump and probe lasers. We show that the 480 nm pump laser, responsible for transitions between the Zeeman sublevels of the intermediate state and the Rydberg state, can be locked to the Zeeman-split EIT peaks. The short-term frequency stability of the laser lock is 0.15 MHz and the long-term stability is within 0.5 MHz. The linewidth of the laser lock is ~0.8 MHz and ~1.8 MHz in the presence and in the absence of the external magnetic field, respectively. In addition, we show that in the absence of an applied magnetic field and adequate shielding, the frequency shift of the lock point has a peak-to-peak variation of 1.6 MHz depending on the polarization of the pump field, while when locked to Zeeman sublevels this variation is reduced to 0.6 MHz. The proposed technique is useful for research involving Rydberg atoms, where large continuous tuning of the laser frequency with stable locking is required.