Laser control of ultracold molecule formation: The case of RbSr

TL;DR

This paper explores laser-based methods for creating ultracold RbSr molecules, comparing multi-level STIRAP techniques and ground-state IR/THz pulse strategies for efficient molecule formation.

Contribution

It introduces and compares novel multi-level STIRAP extensions and ground-state pulse sequences for ultracold molecule synthesis, emphasizing experimental feasibility.

Findings

Both STIRAP extensions effectively transfer population with high efficiency.

IR/THz pulses successfully create and stabilize molecules in their ground state.

Optimal control improves pulse sequences for robustness and efficiency.

Abstract

We have studied the formation of ultracold RbSr molecules with laser pulses. After discussing the advantages of the Mott insulator phase for the control with pulses, we present two classes of strategies. The first class involves two electronic states. Two extensions of stimulated Raman adiabatic passage (STIRAP) for multi-level transitions are used : alternating STIRAP (A-STIRAP) and straddle STIRAP (S-STIRAP). Both transfer dynamics are modeled and compared. The second class of strategies involves only the electronic ground state and uses infrared (IR)/TeraHertz (THz) pulses. The chemical bond is first created by the application of a THz chirped pulse or $\pi$-pulse. Subsequently, the molecules are transferred to their ro-vibrational ground state using IR pulses. For this last step, different optimized pulse sequences through optimal control techniques, have been studied. The relative merits of these strategies in terms of efficiency and robustness are discussed within the experimental feasibility criteria of present laser technology.