Two-photon coherent control of femtosecond photoassociation

Abstract

Photoassociation with short laser pulses has been proposed as a technique to create ultracold ground state molecules. A broad-band excitation seems the natural choice to drive the series of excitation and deexcitation steps required to form a molecule in its vibronic ground state from two scattering atoms. First attempts at femtosecond photoassociation were, however, hampered by the requirement to eliminate the atomic excitation leading to trap depletion. On the other hand, molecular levels very close to the atomic transition are to be excited. The broad bandwidth of a femtosecond laser then appears to be rather an obstacle. To overcome the ostensible conflict of driving a narrow transition by a broad-band laser, we suggest a two-photon photoassociation scheme. In the weak-field regime, a spectral phase pattern can be employed to eliminate the atomic line. When the excitation is carried out by more than one photon, different pathways in the field can be interfered constructively or destructively. In the strong-field regime, a temporal phase can be applied to control dynamic Stark shifts. The atomic transition is suppressed by choosing a phase which keeps the levels out of resonance. We derive analytical solutions for atomic two-photon dark states in both the weak-field and strong-field regime. Two-photon excitation may thus pave the way toward coherent control of photoassociation. Ultimately, the success of such a scheme will depend on the details of the excited electronic states and transition dipole moments. We explore the possibility of two-photon femtosecond photoassociation for alkali and alkaline-earth metal dimers and present a detailed study for the example of calcium.

References in corpus (9)

• Molecule formation in ultracold atomic gases
• Photoassociation of cold atoms with chirped laser pulses: time-dependent calculations and analysis of the adiabatic transfer within a two-state model
• Making ultracold molecules in a two color pump-dump photoassociation scheme using chirped pulses
• Coherent control with shaped femtosecond laser pulses applied to ultracold molecules
• Coherent control of ultracold molecule dynamics in a magneto-optical trap using chirped femtosecond laser pulses
• Short-pulse photoassociation in rubidium below the D${}_1$ line
• Engineering an all-optical route to ultracold molecules in their vibronic ground state
• Enhancement of Intermediate-Field Two-Photon Absorption by Rationally-Shaped Femtosecond Pulses
• Frequency-Domain Coherent Control of Femtosecond Two-Photon Absorption: Intermediate-Field vs. Weak-Field Regime

Cited by in corpus (8)

• Second order gradient ascent pulse engineering
• Interatomic potentials, electric properties, and spectroscopy of the ground and excited states of the Rb_2 molecule: Ab initio calculations and effect of a non-resonant field
• Enhancement of Ultracold Molecule Formation Using Shaped Nanosecond Frequency Chirps
• Optimized production of ultracold ground-state molecules: Stabilization employing potentials with ion-pair character and strong spin-orbit coupling
• Femtosecond two-photon photoassociation of hot magnesium atoms: A quantum dynamical study using thermal random phase wavefunctions
• Semi-global approach for propagation of the time-dependent Schrödinger equation for time-dependent and nonlinear problems
• Coherent control of ultracold 85Rb trap-loss collisions with nonlinearly frequency-chirped light
• Efficient Formation of Ultracold Molecules with Chirped Nanosecond Pulses