Incoherent repumping scheme in the $^{88}$Sr$^{+}$ five-level manifold

TL;DR

This study investigates the complex repumping scheme in laser-cooled $^{88}$Sr$^{+}$ ions, revealing deviations from simple models and identifying optimal conditions for maximizing photon scattering through combined spectroscopy and detailed numerical modeling.

Contribution

It introduces a comprehensive analysis of the $^{88}$Sr$^{+}$ ion's repumping scheme using optical Bloch equations with 18 Zeeman sublevels, providing insights beyond the two-level atom approximation.

Findings

Fluorescence spectra are Lorentzian but cannot be explained by a two-level model.

Optimal repumping conditions for maximum photon scattering are identified.

Width and amplitude of spectra depend on multi-level dynamics, not just simple models.

Abstract

Laser-cooled trapped ions are at the heart of modern quantum technologies and their cooling dynamics often deviate from the simplified two-level atom model. Doppler cooling of the $^{88}$Sr$^{+}$ ion involves several electronic levels and repumping channels that strongly influence fluorescence. In this work, we study a repumping scheme for the $^{88}$Sr$^{+}$ ion by combining precision single-ion spectroscopy with comprehensive numerical modeling based on optical Bloch equations including 18 Zeeman sublevels. We show that, although the observed fluorescence spectra retain a Lorentzian lineshape, their width and amplitude cannot be explained by a two-level atom description. Moreover, we find the optimal repumping conditions for maximizing the photon scattering rate.