Shaping of the time evolution of field-free molecular orientation by THz laser pulses

Abstract

We present a theoretical study of the shaping of the time-evolution of field-free orientation of linear molecules. We show the extend to which the degree of orientation can be steered along a desired periodic timedependent signal. The objective of this study is not to optimize molecular orientation but to propose a general procedure to precisely control rotational dynamics through the first moment of the molecular axis distribution. Rectangular and triangular signals are taken as illustrative examples. At zero temperature, we compute the quantum states leading to such field-free dynamics. A TeraHertz laser pulse is designed to reach these states by using optimal control techniques. The investigation is extended to the case of non-zero temperature. Due to the complexity of the dynamics, the control protocol is derived with a Monte-Carlo simulated annealing algorithm. A figure of merit based on the Fourier coefficients of the degree of orientation is used. We study the robustness of the control process against temperature effects and amplitude variations of the electric field.

Selective Orientation of Chiral Molecules by Laser Fields with Twisted Polarization

“…2(a) and 2(b), which are before and after 0 ps, respectively]. This transient orientation induced by single THz pulses is expected and has been observed before [41][42][43][44][45][46][47][48].…”

Quantum dynamics of a polar rotor acted upon by an electric rectangular pulse of variable duration

“…Whereas either adiabatic interactions [26][27][28][29][30][31][32][33][34][35][36][37][38] or their impulsive, non-adiabatic counterparts [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] have received much attention, interactions with finiteduration pulses have been scarce [54][55][56]. It is the last that are the focus of the present study.…”

Generation of maximal three-state field-free molecular orientation with terahertz pulses

“…Despite the slow progress in experiments, several theoretical proposals have been directed toward the realization of molecular field-free orientation by exclusively using zeroarea terahertz pulses [36][37][38][39][40]. Furthermore, recent theoretical work has shown that a single half-cycle-zero-area terahertz pulse can result in steady molecular orientation a long time after the pulse is turned off [41].…”