Impact of Decoherence on Internal State Cooling using Optical Frequency Combs

TL;DR

This paper investigates how decoherence affects the efficiency of internal state cooling of molecules using optical frequency combs, considering various chirp modulations and their impact on population transfer at ultracold temperatures.

Contribution

It introduces a theoretical model that incorporates decoherence effects in the control of molecular states with optical frequency combs, analyzing chirp effects on population transfer efficiency.

Findings

Odd and even chirps influence population transfer differently.

Decoherence reduces the effectiveness of state transfer.

Chirp modulation can mitigate some decoherence effects.

Abstract

We discuss femtosecond Raman type techniques to control molecular vibrations, which can be implemented for internal state cooling from Feshbach states with the use of optical frequency combs with and without modulation. The technique makes use of multiple two-photon resonances induced by optical frequencies present in the comb. It provides us with a useful tool to study the details of molecular dynamics at ultracold temperatures. In our theoretical model we take into account decoherence in the form of spontaneous emission and collisional dephasing in order to ascertain an accurate model of the population transfer in the three-level system. We analyze the effects of odd and even chirps of the optical frequency comb in the form of sine and cosine functions on the population transfer. We compare the effects of these chirps to the results attained with the standard optical frequency comb to see if they increase the population transfer to the final deeply bound state in the presence of decoherence. We also analyze the inherent phase relation that takes place owing to collisional dephasing between molecules in each of the states. This ability to control the rovibrational states of a molecule with an optical frequency comb enables us to create a deeply bound ultracold polar molecules from the Feshbach state.