Velocity selective bi-polarization spectroscopy for laser cooling of metastable Krypton atoms

TL;DR

This paper introduces a velocity selective bi-polarization spectroscopy (VS-BPS) technique for stable laser cooling of metastable Krypton atoms, offering a tunable, background-free reference signal that improves laser frequency stability.

Contribution

The paper presents a novel VS-BPS method that provides a tunable, background-free dispersion-like signal for laser stabilization in Krypton atom cooling, outperforming traditional saturated absorption spectroscopy.

Findings

VS-BPS signal is tunable via control laser frequency.

Laser locked with VS-BPS shows better frequency stability.

Effective for stabilization and tuning of cooling lasers in Kr* MOT.

Abstract

We report a velocity selective bi-polarization spectroscopy (VS-BPS) technique to generate a background-free, dispersion-like reference signal which is tunable over a wide range of frequency. In this technique, a pair of linearly polarized weak probe beams passing through a gas cell of metastable Krypton (Kr*) atoms, overlaps with a pair of counter-propagating circularly polarized strong pump beams derived from an independently tunable control laser. The polarization spectroscopy signals from the two probe beams, after subtraction, result in VS-BPS signal. The spectral shifting in VS-BPS signal can be achieved by tuning the frequency of the control laser. The dependence of the amplitude and slope of the VS-BPS signal on the RF power used for excitation of Kr atoms in the gas cell and on the power of pump beams has been studied. The frequency stability of a diode laser locked with VS-BPS signal has been found to be better than the frequency stability of the laser locked with a saturated absorption spectroscopy (SAS) signal. The VS-BPS signal is finally used for stabilization and tuning of the cooling laser frequency for a magneto-optical trap (MOT) for Kr* atoms.