Optical pulse-shaping for internal cooling of molecules

TL;DR

This paper explores using pulse-shaped femtosecond lasers to rapidly cool the rotational and vibrational states of molecules, demonstrating both theoretical simulations and experimental pulse shaping for potential applications in molecular cooling.

Contribution

It introduces a novel optical pulse-shaping method for internal molecular cooling that is faster and applicable to a broader range of molecules than previous techniques.

Findings

Simulated rovibrational cooling of AlH+ in 8 microseconds.

Laboratory demonstration of pulse shaping suitable for rotational cooling.

Potential application to apolar molecules with similar ground and excited states.

Abstract

We consider the use of pulse-shaped broadband femtosecond lasers to optically cool rotational and vibrational degrees of freedom of molecules. Since this approach relies on cooling rotational and vibrational quanta by exciting an electronic transition, it is most easily applicable to molecules with similar ground and excited potential energy surfaces, such that the vibrational state is usually unchanged during electronic relaxation. Compared with schemes that cool rotations by exciting vibrations, this approach achieves internal cooling on the orders-of- magnitude faster electronic decay timescale and is potentially applicable to apolar molecules. For AlH+, a candidate species, a rate-equation simulation indicates that rovibrational equilibrium should be achievable in 8 \mu s. In addition, we report laboratory demonstration of optical pulse shaping with sufficient resolution and power for rotational cooling of AlH+.