Field-free molecular orientation by nonresonant and quasiresonant two-color laser pulses

Abstract

International audienceWe analyze the control of molecular orientation by nonresonant and quasiresonant two-color laser pulses (2+1 process). The laser pulses are assumed to be short with respect to the rotational period. In the nonresonant case, we show that the efficiency of this strategy crucially depends on the polarizability and the hyperpolarizability of the molecule. In the quasiresonant case, i.e., if the 2ω frequency is in quasiresonance with a vibrational frequency, one can improve the orientation by adjusting the detuning. The best orientation is obtained for an optimal value of the detuning, which is different from zero

Fully efficient time-parallelized quantum optimal control algorithm

“…Molecular orientation [33,34] is nowadays a wellestablished topic both from the experimental [35,36] and theoretical points of views [37][38][39][40][41]. Different optimal control analyses have been made on this quantum system [42][43][44][45].…”

Observation of the field-free orientation of a symmetric-top molecule by terahertz laser pulses at high temperature

“…At low temperature, a very high degree of orientation can be obtained using such control strategies and a molecular quantum-state selection [32,33,34,35]. Control schemes in the sudden regime, where the duration of the control field is short with respect to the rotational period, have been also developed [36,37,38,39,40,12,41,42,43,44,45,46,47,48,49,50,51,52]. Among other techniques, we can mention the interaction of the molecule with a terahertz (THz) laser pulse and the (ω, 2ω)-scheme.…”

Comparative study of monotonically convergent optimization algorithms for the control of molecular rotation

“…If we further assume that the frequency ω of the laser field is much higher than the rotational frequencies and non-resonant with respect to all rovibronic transitions, we can average over the fast oscillations of the electric field in Eq. (3) and obtain [35,34]:…”

“…The Hamiltonian of the system can be written as [34,35]: where B is the rotational constant. The first term of the right-hand side of Eq.…”

“…The control of molecular rotation [26,27,28,29,30,31,32,33], for which such non-linear models are well established [34,35], is used as a testbed case to analyze the features of these algorithms. A first modification of a monotonically convergent algorithm to account for a non-linear interaction with the control assumes the cost to be quadratic in the field and decomposes the control into n components for a nonlinearity of order n [24].…”