Optical force on two-level atoms by few-cycle-pulse Gaussian laser fields beyond the rotating-wave approximation

Kumar, Pankaj; Sarma, Amarendra K.

doi:10.1103/physreva.84.043402

Cited by 22 publications

(10 citation statements)

References 32 publications

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“…In this work, we have used optical Bloch equations without invoking the rotating wave approximations (RWA) as we are dealing with intense few-cycle pulse of femtosecond duration. The reasons for using non-rotating wave approximation are well explained by many authors [34][35][36]. In equation ( 1) we present the optical Bloch equations without invoking the RWA: (1) In these equations γ ij , ω ω ω = − ij i j and Ω ij denote the spontaneous decay rate, the difference in energy levels and the Rabi frequency corresponding to the pulsed radiation respectively for the energy level pair |i > and |j > .We have assumed that the pair of transitions |1 > to |2 > and |3 > to |4 > are dipole forbidden and the rate of decoherence between the two ground states |1 > and |2 > is negligible and has no influence over the time-scales involved in the interaction with the pulse train.…”

Section: The Modelmentioning

confidence: 99%

High and uniform coherence creation in Doppler-broadened double Λ-like atomic system by a train of femtosecond optical pulses

Sarma¹,

Kumar²

2015

Laser Phys.

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We present a detailed analysis of coherence creation in a four level double Ʌ-like atomic system using a train of ultra-short few-cycle Gaussian pulses. The effect of the Doppler broadening has been analyzed. It is possible to create high coherence across all the velocity groups in the atomic ensemble using pulses with low repetition frequency. The accumulation of coherence at different radial locations within the atomic beam cross-section as a function of the number of pulses in the train is also reported. We find that pulse train with lower repetition frequencies are able to generate high and nearly uniform coherence in a substantial part of the atomic system. I. INTRODUCTIONSince the first experimental demonstration of coherent population trapping (CPT) in Ʌ-type system [1], numerous investigations have been made into coherence-induced phenomena like electromagnetically induced transparency (EIT), absorption (EIA), etc. [2][3][4][5][6][7]. In fact, recently a theoretical investigation shows that CPT can occur even in buckminsterfullerene C60 [8]. Arguably, one of the primary reasons behind such an interest is the possibility of modifying the optical properties of the media through quantum interference. Extremely narrow absorption and emission spectral features [9] are associated with CPT and have been identified for use in the implementation of atomic frequency standards [10][11]. Again, the phenomenon of CPT is used to reduce the group velocity of light significantly in certain media [12]. The coherence accumulated in a system can give rise to effects like enhancement of refractive index with zero absorption [13][14][15], light amplification without population inversion [16], high-harmonic generation [17], etc. Kocharovskaya and Khanin predicted the possibility of using a train of pulses to create coherence in 1986 [18] and later demonstrated experimentally by making use of a comb of optical pulses produced from a mode-locked diode laser [19]. With the recent progress in generation of well-characterized short optical pulses it has become possible to accumulate the coherence in a robust and controllable fashion [20][21]. More recently authors have made theoretical investigations into the generation of coherence using a series of short pulses [22][23][24]. In particular, Aumiler [20] investigated EIT of a train of femtosecond pulses interacting with the four level atomic systems in the conditions when the pulse repetition period is shorter than the characteristic atomic relaxation times. He considered a special case where the pulse repetition frequency is a subharmonic of the hyperfine splitting of the ground state. Aumiler's works illustrate how the judicious choice of the frequency comb parameters can provide means to effectively control the degree of coherence between the ground-state hyperfine levels for selective velocity groups of atoms. In this work we present a detailed analysis of coherence creation between the two lower states of a four level double Ʌ-like atomic system using a train of ultra-short f...

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Section: The Modelmentioning

confidence: 99%

High and uniform coherence creation in Doppler-broadened double Λ-like atomic system by a train of femtosecond optical pulses

Sarma¹,

Kumar²

2015

Laser Phys.

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“…Note that we have analyzed the optical force and the corresponding potential by numerically solving the density matrix equations of motion without invoking the RWA. This work is loosely related to studies by our group [34,35] or by others on atomic motion in electromagnetic waves [32,36].…”

Section: Introductionmentioning

confidence: 99%

“…In this context, optical forces have been also used for manipulation and enantioseparation of chiral droplets [27], chiral molecules [28], and chiral nanoparticles [29,30]. More recently, a resurgence of interest in optical trapping with femtosecond (fs) pulses is occurring [31][32][33][34][35], because of the tremendous technological advancement in the generation of such laser pulses.…”

Section: Introductionmentioning

confidence: 99%

Chirality-dependent optical dipole potential

Kazemi

Mahmoudi

2020

Phys. Scr.

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In this paper, we show the possibility of spatially separating two opposite enantiomers of chiral molecules, using an optical dipole potential. Because of the broken mirror symmetry of effective potential, chiral molecules have a cyclic three-level Δ-configuration structure. Irradiation of these molecules with three femtosecond laser pulses gives rise to an enantiomer-dependent optical force. Interestingly, considerable differences in the direction of the force felt by the enantiomers have been shown to cause the chirality-dependent optical dipole potential which stably captures only one enantiomeric form. Moreover, the proposed scheme provides a complete control over what kind of molecules, the left- or right-handed ones, can be selectively trapped. Note that we have analyzed the optical force, and specifically the trapping effect, by considering the full interaction Hamiltonian, including both rotating and counter-rotating terms.

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“…Cheng and Zhou [22] demonstrated numerically, without using the so-called rotating-wave approximation (RWA), the ultrafast population transfer in -like three-state atomic systems with frequency-chirped few-cycle femtosecond laser pulses, though the scheme was not found to be robust against the variation of laser-pulse parameters. In passing, it should be mentioned that RWA may not hold when one deals with few-cycle-pulserelated phenomena and should work in the non-RWA regime [13,[23][24][25][26]. Recently, Shapiro et al [27,28] proposed a new * aksarma@iitg.ernet.in method, the so-called piecewise rapid adiabatic passage (PAP), for executing complete population transfer between quantum states in a piecewise manner using a series of femtosecond laser pulses.…”

Section: Introductionmentioning

confidence: 99%

Gaussian and sinc-shaped few-cycle-pulse-driven ultrafast coherent population transfer inΛ-like atomic systems

Kumar

Sarma

2012

Phys. Rev. A

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We report and propose a simple scheme to achieve efficient and fast coherent population transfer by utilizing either a nonlinearly chirped Gaussian-shaped few-cycle laser pulse or an unchirped sinc-shaped few-cycle laser pulse. The proposed scheme is shown to be fairly robust against the variation of the laser parameters such as temporal pulse width, chirp rates, carrier-envelope phases, and Rabi frequencies. We find that compared to the so-called stimulated Raman adiabatic passage technique, our scheme for complete population transfer with few-cycle Gaussian-shaped laser pulses requires less pulse area.

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Optical force on two-level atoms by few-cycle-pulse Gaussian laser fields beyond the rotating-wave approximation

Cited by 22 publications

References 32 publications

High and uniform coherence creation in Doppler-broadened double Λ-like atomic system by a train of femtosecond optical pulses

High and uniform coherence creation in Doppler-broadened double Λ-like atomic system by a train of femtosecond optical pulses

Chirality-dependent optical dipole potential

Gaussian and sinc-shaped few-cycle-pulse-driven ultrafast coherent population transfer inΛ-like atomic systems

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