Enhancement of Ultracold Molecule Formation Using Shaped Nanosecond Frequency Chirps

TL;DR

This paper shows that carefully shaped nanosecond frequency chirps can significantly boost ultracold molecule formation rates by optimizing adiabatic transitions and minimizing spontaneous emission effects.

Contribution

It introduces a novel method of shaping frequency chirps to enhance ultracold molecule production, supported by experimental results and quantum simulations.

Findings

Enhanced molecule formation rate with shaped chirps

Chirp shapes improve adiabatic transition efficiency

Quantum simulations confirm the enhancement mechanism

Abstract

We demonstrate that judicious shaping of a nanosecond-time-scale frequency chirp can dramatically enhance the formation rate of ultracold $^{87}$Rb$_{2}$ molecules. Starting with ultracold $^{87}$Rb atoms, we apply pulses of frequency-chirped light to first photoassociate the atoms into excited molecules and then, later in the chirp, de-excite these molecules into a high vibrational level of the lowest triplet state, $a \, ^{3}\Sigma_{u}^{+}$. The enhancing chirp shape passes through the absorption and stimulated emission transitions relatively slowly, thus increasing their adiabaticity, but jumps quickly between them to minimize the effects of spontaneous emission. Comparisons with quantum simulations for various chirp shapes support this enhancement mechanism.