Rubidium atom spectral lineshapes in high intensity electric fields near an optical nanofibre

TL;DR

This paper investigates how high-intensity electric fields near an optical nanofibre affect the spectral lineshapes of cold rubidium atoms, revealing complex fluorescence profiles crucial for nonlinear optical experiments.

Contribution

It provides the first detailed analysis of rubidium spectral lineshapes under strong excitation near nanofibres, highlighting the interplay of excitation and atom pushing effects.

Findings

Observation of two-peak fluorescence profile near resonance

Resonance scattering significantly alters fluorescence signals

High electric fields enable nonlinear optical processes

Abstract

The integration of cold atomic systems with optical nanofibres is an increasingly important experimental platform. Here, we report on the spectra observed during a strongly driven, single-frequency, two-photon excitation of cold rubidium atoms near an optical nanofibre. At resonance, two competitive processes, namely a higher excitation rate and stronger pushing of atoms from the nanofibre due to resonance scattering, need to be considered. We discuss the processes that lead to the observed two-peak profile in the fluorescence spectrum as the excitation laser is scanned across the resonance, noting that the presence of the optical nanofibre dramatically changes the fluorescence signal. These observations are useful for experiments where high electric field intensities near an ONF are needed, for example when driving nonlinear processes.