STIRAP method

V. Kurkal and S. A. Rice. Sensitivity of the extended STIRAP method of selective population transfer to coupling to background states. J. Phys. Chem. B, 105(28) 6488-6494(2001). 

Up to now we have only considered the population changes ANi under SEP. There are, however, also coherent effects and an even more efficient scheme for population transfer is provided by the coherent stimulated rapid adiabatic passage (STIRAP) method, explained in Chap. 7. 

The STIRAP method has attracted considerable interest as a highly efficient way to coherently transfer atom pairs or Feshbach molecules into a more deeply bound state [85]. The method offers a high transfer efficiency without heating of the molecular... 

An even more efficient scheme is provided by the coherent STImu-lated Rapid Adiabatic Passage (STIRAP) method, explained in Chap. 12. 

Coherent population transfer Transfer of population from one quantum mechanical level to another using coherent radiation. The radiation may be provided by either continuous or pulsed lasers. Using the method of adiabatic passage (see STIRAP), 100% population transfer has been achieved. 

Population transfer in a three-level system can be achieved by using one laser (known as the pump laser, which may be either continuous wave or pulsed) to connect the ground and intermediate levels, and a second laser (the Stokes laser ) to connect the intermediate and final levels. This method, known as stimulated Raman adiabatic passage or STIRAP, is illustrated in Fig. 22. In this example, the three levels have a A-type configuration, where... 

Ordinary STIRAP is only sensitive to the energy levels and the magnitudes of transition-dipole coupling matrix elements between them. These quantities are identical for enantiomers. Its insensitivity to the phase of the transition-dipole matrix elements renders STIRAP incapable of selecting between enantiomers. Recently we have demonstrated [11] that precisely the lack of inversion center, which characterizes chiral molecules, allows us to combine the weak-field one-and two-photon interference control method [29,54,95,96] with, the strong-field STIRAP to render a phase-sensitive AP method. In this method, which we termed cyclic population transfer (CPT), one forms a STIRAP loop by supplementing the usual STIRAP 1) o 2) <=> 3) two-photon process by a one-photon process 1) <=> 3). The lack of inversion center is essentrat, because one-photon and two-photon processes cannot connect the same states in the presence of an inversion center, where all states have a well defined parity, because a one-photon absorption (or emission) between states 1) and 3) requires that these states have opposite parities, whereas a two-photon process requires that these states have the same parity. 

Complete population transfer in AP was shown theoretically [20] and independently implemented experimentally a few years later in a method called STIRAP [21, 187]. In this method, which is a variant of the stimulated Raman process, the two ("pump" and "Stokes") pulses are employed in the reverse ("counter-intuitive") order to that of the usual stimulated Raman process, namely in STIRAP the Stokes pulse precedes the pump pulse. This method designed to work with discrete states clearly complements CC by being able to transfer populations completely but at the same time not being phase sensitive, in contrast to the CC that is typically used in continua of states in weak-field but phase-sensitive regimes. We later explore the advantages resulting from the combination of both approaches. 

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