Implementation of a single femtosecond optical frequency comb for rovibrational cooling

TL;DR

This paper demonstrates that a single femtosecond optical frequency comb, with or without phase modulation, can efficiently induce two-photon transitions to produce ultracold molecules, enabling rovibrational cooling.

Contribution

It introduces a novel method using a single femtosecond optical frequency comb with phase modulation for molecular cooling and state transfer.

Findings

Phase modulation enhances population transfer efficiency.

Both modulated and unmodulated combs achieve complete population transfer.

The method enables controlled rovibrational cooling of molecules.

Abstract

We show that a single femtosecond optical frequency comb may be used to induce two-photon transitions between molecular vibrational levels to form ultracold molecules, e.g., KRb. The phase across an individual pulse in the pulse train is sinusoidally modulated with a carefully chosen modulation amplitude and frequency. Piecewise adiabatic population transfer is fulfilled to the final state by each pulse in the applied pulse train providing a controlled population accumulation in the final state. Detuning the pulse train carrier and modulation frequency from one-photon resonances changes the time scale of molecular dynamics but leads to the same complete population transfer to the ultracold state. A standard optical frequency comb with no modulation is shown to induce similar dynamics leading to rovibrational cooling.