Coherent Bichromatic Force Deflection of Molecules

TL;DR

This paper demonstrates the application of a coherent bichromatic optical force to deflect molecules, specifically SrOH, enabling efficient manipulation of molecular motion with minimal losses, and compares experimental results with theoretical models.

Contribution

It is the first demonstration of a bichromatic force on a molecule, showing controlled deflection and momentum transfer with minimal dark state loss.

Findings

Achieved 70ħk momentum transfer to SrOH molecules.

Reversed force direction by adjusting laser phase.

Model matches experimental results, confirming theoretical understanding.

Abstract

We demonstrate the coherent optical bichromatic force on a molecule, the polar free radical strontium monohydroxide (SrOH). A dual-frequency retro-reflected laser beam addressing the $\tilde{X}^2\Sigma^+\leftrightarrow\tilde{A}^2\Pi_{1/2}$ electronic transition coherently imparts momentum onto a cryogenic beam of SrOH. This directional photon exchange creates a bichromatic force that transversely deflects the molecules. By adjusting the relative phase between the forward and counter propagating laser beams we reverse the direction of the applied force. A momentum transfer of $70\hbar k$ is achieved with minimal loss of molecules to dark states. Modeling of the bichromatic force is performed via direct numerical solution of the time-dependent density matrix and is compared with experimental observations. Our results open the door to further coherent manipulation of molecular motion, including the efficient optical deceleration of diatomic and polyatomic molecules with complex level structures.