Asymmetric effect of slowly varying chirped laser pulses on the adiabatic state exchange of a molecule

Gilary, Ido; Moiseyev, Nimrod

doi:10.1088/0953-4075/45/5/051002

Cited by 36 publications

(41 citation statements)

References 11 publications

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“…This is an example where the specificity of resonances derived from a purely adiabatic Floquet model is used in a wave-packet propagation scheme aiming at quantum purification control. We emphasize that, due to continuous adiabatic transport of the initial field-free state on its corresponding ZWRs at all times (intensities starting from zero), the strategy does not suffer from a possible nonadiabatic contamination as has recently been discussed in the context of EPs [15]. The present results go much beyond some previous works where either only the passage through ZWRs at fixed wavelength was at the basis of a filtering [9] or only ZWRs were used as a last step in a cooling process based on EPs [16].…”

Section: -3mentioning

confidence: 93%

Proposal for laser purification in molecular vibrational cooling using zero-width resonances

et al. 2013

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Intense-field molecular photodissociation offers the possibility to define resonances of zero width for particular intensities at given wavelengths. We show how a laser pulse can be shaped to fulfill, at all times, the conditions leading to a zero width for a particular resonance originating from a field-free vibrational state. The solution of the time-dependent Schrödinger equation confirms that only this state survives after the pulse is off. This is the basis for a purification procedure leading to population left only in a single state chosen at will. Purification, to get a single vibrational (or rotational) state out of an ensemble of initial ones, is an important issue in the laser control of molecular dynamics. In particular, molecular rovibrational cooling is a major challenge which necessitates a selective preparation of a single rovibrational state starting from an initial distribution, either thermal or resulting from photoassociation [1]. Among other techniques, vibrational cooling has experimentally been achieved referring to blackbody-radiation-assisted lasers [2,3] or optical pumping by broadband femtosecond lasers [4]. In particular, methods involving photoassociation of ultracold atoms are able to produce translationally cold tightly bound molecules in a given electronic state. Additional sequences of shaped laser pulses are used to transfer most of these molecules in their ground vibrational state. All these processes involve a decay mechanism which describes the unavoidable entropy flow, a key concept in purification [5].For this purpose, we have recently proposed an adiabatic vibrational population transport mechanism using exceptional points (EPs) corresponding to two coalescing resonances for a specific laser wavelength and intensity [6]. A chirped pulse encircling the EP monitors the vibrational transfer between two adjacent resonances originating from field-free vibrational states v + 1 and v. The residual populations, after the pulse is over, could then be transferred step by step to state v = 0, using successive pulses. Contrary to a stimulated Raman adiabatic passage (STIRAP) technique which, by itself, is not fully appropriate for the purification purpose as it does not offer a dissipative channel where the entropy goes, this cooling strategy clearly involves a dissociative process. But it suffers from a compromise to ensure the underlying adiabatic transport. In particular, a long pulse duration to fulfill the requirement of adiabaticity may have, as a consequence, * osman.atabek@u-psud.fr † Also at U. F. R. an important depletion of the overall molecular population through photodissociation. A much more robust purification technique that we propose in this Rapid Communication is to start from a given vibrational distribution and to appropriately shape a single laser pulse, such as to efficiently photodissociate all vibrational states, with the exception of one. The entropy flow is merely associated with the photodissociation process. The mechanism we are referring to when shaping su...

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Section: -3mentioning

confidence: 93%

Proposal for laser purification in molecular vibrational cooling using zero-width resonances

et al. 2013

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“…The requirement of step (i) leading to the approximation of Eq. (26), is expected to be reached for slowly enough (adiabatically) varying parameters (t) avoiding any degeneracy between complex eigenvalues E v { (t)}, at all times t [28]. The second step (ii) involves an optimal choice for the field parameters: * (t) ≡ {E * (t), ω * eff (t)} such that:…”

Section: Zero-width Resonance Strategymentioning

confidence: 99%

Controlling vibrational cooling with zero-width resonances: An adiabatic Floquet approach

et al. 2016

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In molecular photodissociation, some specific combinations of laser parameters (wavelength and intensity) lead to unexpected Zero-Width Resonances (ZWR), with in principle infinite lifetimes. Their interest in inducing basic quenching mechanisms have recently been devised in the laser control of vibrational cooling through filtration strategies [O. Atabek et al., Phys. Rev. A87, 031403(R) (2013)]. A full quantum adiabatic control theory based on the adiabatic Floquet Hamiltonian is developed to show how a laser pulse could be envelop-shaped and frequency-chirped so as to protect a given initial vibrational state against dissociation, taking advantage from its continuous transport on the corresponding ZWR, all along the pulse duration. As compared with previous control scenarios actually suffering from non-adiabatic contamination, drastically different and much more efficient filtration goals are achieved. A semiclassical analysis helps in finding and interpreting a complete map of ZWRs in the laser parameter plane. In addition, the choice of a given ZWR path, among the complete series identified by the semiclassical approach, amounts to be crucial for the cooling scheme, targeting a single vibrational state population left at the end of the pulse, while all others have almost completely decayed. The illustrative example, offering the potentiality to be transposed to other diatomics, is Na2 prepared by photoassociation in vibrationally hot but translationally and rotationally cold states.

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“…These adiabatic interaction properties have been confirmed by tracking the instantaneous eigenstates in the quasi-stationary limit. The complete dynamics of state evolution in non-Hermitian systems with significant imaginary eigenvalue splitting in general involve highly non-adiabatic behaviour associated with an anti-adiabatic state jump occurring under appropriate initial-state and parametric conditions21222324. The anti-adiabatic state jump is a key interaction leading to the time-asymmetric state-evolution passages in our proposed system.…”

Section: Resultsmentioning

confidence: 94%

Extremely broadband, on-chip optical nonreciprocity enabled by mimicking nonlinear anti-adiabatic quantum jumps near exceptional points

et al. 2017

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Time-asymmetric state-evolution properties while encircling an exceptional point are presently of great interest in search of new principles for controlling atomic and optical systems. Here, we show that encircling-an-exceptional-point interactions that are essentially reciprocal in the linear interaction regime make a plausible nonlinear integrated optical device architecture highly nonreciprocal over an extremely broad spectrum. In the proposed strategy, we describe an experimentally realizable coupled-waveguide structure that supports an encircling-an-exceptional-point parametric evolution under the influence of a gain saturation nonlinearity. Using an intuitive time-dependent Hamiltonian and rigorous numerical computations, we demonstrate strictly nonreciprocal optical transmission with a forward-to-backward transmission ratio exceeding 10 dB and high forward transmission efficiency (∼100%) persisting over an extremely broad bandwidth approaching 100 THz. This predicted performance strongly encourages experimental realization of the proposed concept to establish a practical on-chip optical nonreciprocal element for ultra-short laser pulses and broadband high-density optical signal processing.

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Asymmetric effect of slowly varying chirped laser pulses on the adiabatic state exchange of a molecule

Cited by 36 publications

References 11 publications

Proposal for laser purification in molecular vibrational cooling using zero-width resonances

Proposal for laser purification in molecular vibrational cooling using zero-width resonances

Controlling vibrational cooling with zero-width resonances: An adiabatic Floquet approach

Extremely broadband, on-chip optical nonreciprocity enabled by mimicking nonlinear anti-adiabatic quantum jumps near exceptional points

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