Stimulated Raman Adiabatic Passage Scheme Research Articles

Broadband adiabatic mode division (de)multiplexer in thin film lithium niobate

We report a broadband adiabatic mode division (de)multiplexer in a thin film lithium niobate (TFLN) waveguide based on the stimulated Raman adiabatic passage scheme. This particular adiabatic tunneling process is implemented in a three-waveguide structure, in which the intermediate waveguide is tilted relative to the outer waveguides. The excitation of the intermediate waveguide is negligible during the mode (de)multiplexing. A taper structure is included in the intermediate waveguide to ensure efficient mode conversion. The proposed (de)multiplexer can realize multiplexing or demultiplexing of the modes TE0, TE1, and TE2. The structural parameters are determined by simulation, and the results show that conversion efficiencies of 96.3% and 94.6% can be obtained for TE2 and TE1, while the 1-dB operation bandwidth is around 420 nm. The cross talks of TE2, TE1, and TE0 are lower than −13.4dB, −16.4dB, and −34.2dB. The designed (de)multiplexer has relatively good fabrication tolerance. Therefore, it is suitable in TFLN integrated chips.

Stimulated Raman adiabatic passage with trains of weak pulses* *This work is dedicated to Bruce Shore, a brilliant and inspiring physicist, a pioneer in coherent light–matter interaction theory, a mentor and a friend.

We consider coherent population transfer in multilevel quantum systems driven by time-delayed pulse trains. We show how to choose the parameters of the trains so that the population dynamics tracks the behavior of a Λ-type three-level system under stimulated Raman adiabatic passage (STIRAP). Efficient population transfer can be achieved regardless of the order and with or without overlap of the pump and the Stokes sub-pulses of the trains. Generalized STIRAP schemes of population transfer in N-level system with sequential couplings are also examined. The mechanism of the population transfer and the robustness of the proposed schemes are discussed.

Full optical preparation of an absolute ground-state ultracold CsYb molecule via laser-assisted self-induced Feshbach resonance

We investigate theoretically the formation of an ultracold CsYb molecule in the absolute ground state by full optical control. The laser-assisted self-induced Feshbach resonance takes place when the trap state in the optical lattice is coupled with a rovibrational state of the ground electronic state. The Feshbach molecule is formed in the resonant rovibrational state via an adiabatic population transfer by ramping the frequency of a chirped pulse. Two schemes are designed to prepare the absolute ground-state molecule starting from the Feshbach molecule: a pump–dump scheme controlled by short pulses and a stimulated-Raman-adiabatic-passage (STIRAP) scheme steered by long pulses. The probabilities of converting the Feshbach molecule to the absolute ground state molecule by using the pump–dump and the STIRAP schemes are 16% and 99%, respectively.

Plasmonic loss-mitigating broadband adiabatic polarizing beam splitter.

The intriguing analogy between quantum physics and optics has inspired the design of unconventional integrated photonics devices. In this paper, we numerically demonstrate a broadband integrated polarization beam splitter (PBS) by implementing the stimulated Raman adiabatic passage (STIRAP) technique in a three-waveguide plasmonic system. Our proposed PBS exhibits >250 nm transverse-magnetic (TM) bandwidth with <-40 dB extinction and >150 nm transverse-electric (TE) bandwidth with <-20 dB extinction, covering the entire S-, C-, and L-bands and part of the E-band. Moreover, near-lossless light transfer is achieved in our system despite the incorporation of a plasmonic hybrid waveguide because of the unique loss mitigating feature of the STIRAP scheme. Through this approach, various broadband integrated devices that were previously impossible can be realized, which will allow innovation in integrated optics.

Formation of ultracold heteronuclear polyatomic molecule: multi-path scheme and interference effect

We investigate the creation of stable heteronuclear polyatomic molecules based on the three-body and higher order Efimov state via a generalized stimulated Raman adiabatic passage scheme. Within the mean-field approximation, we establish the multi-path conversion models and derive the dark state solutions. The multi-path atom–polymer conversion dynamics and interference effect are studied. We show that the multi-path constructive interference permits higher conversion efficiency, resulting in a state that is closer to the ideal dark state solutions. The effects on the conversion efficiency of the single-photon detuning, the strength of the Rabi pulse, the spontaneous emission from intermediate states and the interaction between the particles are also discussed. Our results not only include the previous ultracold molecule formation techniques, such as the single-path polyatomic molecule, double-path pentamer and triple-path trimer, but also open a possible route for the multi-path formation of more complex polyatomic molecules.

Adiabatic Population Transfer Based on a Double Stimulated Raman Adiabatic Passage

Stimulated Raman adiabatic passage (STIRAP) is an adiabatic population-transfer technique that uses two coherent laser pulses in counter-intuitive order, namely, pump and stoke, to achieve complete transfer between two quantum states. Here, we propose a double STIRAP scheme whereby the electronic levels of a four-level atom are coupled by three laser fields forming two pairs of stoke and pump pulses. We derive the optical Bloch equations through the master equation for studying the population dynamics. We show that manipulating the time between two STIRAP sequences provides the state transfer near unity. In particular, we show that there occurs a certain maximum transfer efficiency that can be achieved in the double STIRAP process.

Breakdown of adiabatic transfer of light in waveguides in the presence of absorption

In atomic physics, adiabatic evolution is often used to achieve a robust and efficient population transfer. Many adiabatic schemes have also been implemented in optical waveguide structures. Recently there has been increasing interest in the influence of decay and absorption, and their engineering applications. Here it is shown that even a small decay can significantly influence the dynamical behavior of a system, above and beyond a mere change of the overall norm. In particular, a small decay can lead to a breakdown of adiabatic transfer schemes, even when both the spectrum and the eigenfunctions are only sightly modified. This is demonstrated for the generalization of a stimulated Raman adiabatic passage scheme that has recently been implemented in optical waveguide structures. Here the question how an additional absorption in either the initial or the target waveguide influences the transfer property of the scheme is addressed. It is found that the scheme breaks down for small values of the absorption at a relatively sharp threshold, which can be estimated by simple analytical arguments.

Formation ofN-body polymer molecules through generalized stimulated Raman adiabatic passage

We investigate the creation of stable homonuclear and heteronuclear $N$-body polymer molecules from ultracold atoms via a generalized stimulated Raman adiabatic passage scheme. The atom-molecule dark-state solutions for the system are obtained and are found to satisfy universal algebraic equations. We discuss the linear instability and the adiabatic fidelity of the dark state. We also explore the effects of the interparticle interactions, the atomic number of the polymer, and external field parameters on the conversion process.

Stimulated Raman adiabatic passage as a route to achieving optical control in plasmonics

Optical properties of ensembles of three-level quantum emitters coupled to plasmonic systems are investigated employing a self-consistent model. It is shown that the stimulated Raman adiabatic passage (STIRAP) technique can be successfully adopted to control optical properties of hybrid materials with collective effects present and playing an important role in light-matter interactions. We consider a core-shell nanowire composed of a silver core and a shell of coupled quantum emitters and utilize a STIRAP scheme to control the scattering efficiency of such a system in a frequency and spatially dependent manner. After the STIRAP-induced population transfer to the final state takes place, the core-shell nanowire exhibits two sets of Rabi splittings with Fano line shapes, indicating strong interactions between two different atomic transitions driven by plasmon near-fields.

Creation of UltracoldSr2Molecules in the Electronic Ground State

We report on the creation of ultracold (84)Sr(2) molecules in the electronic ground state. The molecules are formed from atom pairs on sites of an optical lattice using stimulated Raman adiabatic passage (STIRAP). We achieve a transfer efficiency of 30% and obtain 4×10(4) molecules with full control over the external and internal quantum state. STIRAP is performed near the narrow (1)S(0)-(3)P(1) intercombination transition, using a vibrational level of the 1(0(u)(+)) potential as an intermediate state. In preparation of our molecule association scheme, we have determined the binding energies of the last vibrational levels of the 1(0(u)(+)), 1(1(u)) excited-state and the X (1)Σ(g)(+) ground-state potentials. Our work overcomes the previous limitation of STIRAP schemes to systems with magnetic Feshbach resonances, thereby establishing a route that is applicable to many systems beyond alkali-metal dimers.

Creating pentamer molecules by generalized stimulated Raman adiabatic passage

We study the formation of stable homonuclear and heteronuclear pentamers from ultracold atoms via a generalized stimulated Raman adiabatic passage scheme. The atom-molecule dark-state solutions for the system are obtained, and the linear instability and the adiabatic fidelity of the dark state are investigated. We also discuss the effects of external field parameters on the conversion efficiency.

Phase transitions and dark-state physics in two-color superradiance

We theoretically study an extension of the Dicke model, where the single-particle Hamiltonian has three energy levels in Lambda-configuration, i.e. the excited state is coupled to two non-degenerate ground states via two independent quantized light fields. The corresponding many-body Hamiltonian can be diagonalized in the thermodynamic limit with the help of a generalized Holstein--Primakoff transformation. Analyzing the ground-state energy and the excitation energies, we identify one normal and two superradiant phases, separated by phase transitions of both first and second order. A phase with both superradiant states coexisting is not stable. In addition, in the limit of two degenerate ground states a dark state emerges, which seems to be analogous to the dark state appearing in the well known stimulated Raman adiabatic passage scheme.

Stimulated Raman adiabatic passage in an extended ladder system

The rovibrational dynamics of an extended ladder stimulated Raman adiabatic passage (STIRAP) system through permanent dipole moment transitions is investigated theoretically using the time-dependent quantum-wave-packet method for the ground electronic state of the HF molecule. The calculated results show that nearly 100$%$ of the population can be transferred to the target state through (1+2), (1+3), and (2+2) STIRAP schemes. By choosing a suitable excitation pathway, the effects of the background states on the final population of the target state can be removed. For the multiphoton STIRAP process, the one-photon overtone pump scheme is more efficient than the two-photon pump scheme in controlling the population transfer to the target state.

Adiabatic conversion of ultracold atoms to A3B-type tetrameric molecules

We investigate the conversion of ultracold bosonic atoms to heteronuclear tetramer A3B by an Efimov resonance-assisted stimulated Raman adiabatic passage scheme. In view of recent experiments involving heteronuclear Efimov trimers KKRb and KRbRb [Phys. Rev. Lett. 103, 043201 (2009)], the intermediate state populated by heteronuclear trimer A2B in the conversion process is considered. The atom-molecule dark state solution for a system with a population imbalance is derived analytically, and the role played by the imbalance in the conversion is studied. In addition, the effects of the external field parameters (including photoassociated pulse intensity, width, magnetic coupling strength and its detuning) on the conversion are discussed via the concept of adiabatic fidelity.

Formation of a heteronuclear tetramerA3Bvia Efimov-resonance-assisted stimulated Raman adiabatic passage

We investigate the formation of a heteronuclear tetramer ${A}_{3}B$ by an Efimov-resonance-assisted stimulated Raman adiabatic passage scheme, which is considered a viable means of creating the homonuclear tetramer ${A}_{4}$ [H. Jing and Y. Jiang, Phys. Rev. A 77, 065601 (2008)]. The atom-molecule dark-state solution for the system is derived, and the adiabatic conversion from atoms to heteronuclear tetramers is studied via the concept of adiabatic fidelity. In addition, the effects of external field parameters (including Rabi pulse strength, width, and single photon detuning) on the conversion are discussed.

Exact quantum dissipative dynamics under external time-dependent driving fields

An exact and nonperturbative quantum master equation can be constructed via the calculus on the path integral. It results in hierarchical equations of motion for the reduced density operator. Involved also are a set of well-defined auxiliary density operators that resolve not just the system–bath coupling strength but also memory. In this work, we scale these auxiliary operators individually to achieve a uniform error tolerance, as set by the reduced density operator. An efficient propagator is then proposed to the hierarchical Liouville-space dynamics of quantum dissipation. Numerically exact studies are carried out on the dephasing effect on population transfer in the simple stimulated Raman adiabatic passage scheme. We also make assessments on several perturbative theories for their applicabilities in the present system of study.

ADIABATICITY OF THE DARK STATE IN A NONLINEAR ATOM-TRIMER CONVERSION SYSTEM

We investigate the adiabaticity of the dark state in a nonlinear atom-trimer conversion system in a stimulated Raman adiabatic passage (STIRAP). We find that, in the absence of the nonlinear collisions, the adiabatic condition for this nonlinear system only depends on the Rabi-frequency of the dimer-trimer coupling optical field, which is different from traditional STIRAP processes. In the presence of the nonlinear collisions, the adiabatic condition also relies on the atom-dimer coupling Rabi frequency. However, its influence is really small. Moreover, we propose a more feasible two-photon STIRAP scheme that has better adiabaticity and hence could yield higher atom-trimer conversion efficiency.

Linear instability and adiabatic fidelity for the dark state in a nonlinear atom-trimer conversion system

We investigate the linear instability and the adiabatic fidelity of a dark state in a nonlinear atom-trimer conversion that is implemented by a stimulated Raman adiabatic passage (STIRAP). We find that the interparticle interactions could induce the instability of the atom-trimer dark state in some parameter regimes. We also discuss the adiabatic evolution of the dark state in terms of a newly defined adiabatic fidelity. Based on our theoretical analysis, we propose a feasible two-photon STIRAP scheme that has high adiabatic fidelity, less instability, and therefore could yield high atom-trimer conversion efficiency.

The double dark resonance in a cold gas of Cs atoms and molecules

We theoretically investigated the properties of the effective four-level stimulated Raman adiabatic passage scheme in a cold gas of Cs atoms and molecules, where exists the tunnelling coupling between two excited molecular states due to the 0(g)- (6S,6P(3/2)) double well structure. The double dark resonance is predicted in the absorption spectrum when the tunnelling coupling strength is large enough. The double dark resonance not only reveals the formation of the ultra-cold molecules, but also provides further evidence for the tunnelling as one effective coupling mechanism between the two excited molecular states. The effect of the various experimental conditions on this phenomena has been discussed.

Mean-field dynamics of a Bose-Einstein condensate in a time-dependent triple-well trap: Nonlinear eigenstates, Landau-Zener models, and stimulated Raman adiabatic passage

We investigate the dynamics of a Bose-Einstein condensate in a triple-well trap in a three-level approximation. The interatomic interactions are taken into account in a mean-field approximation (Gross-Pitaevskii equation), leading to a nonlinear three-level model. Additional eigenstates emerge due to the nonlinearity, depending on the system parameters. Adiabaticity breaks down if such a nonlinear eigenstate disappears when the parameters are varied. The dynamical implications of this loss of adiabaticity are analyzed for two important special cases: A three-level Landau-Zener model and the stimulated Raman adiabatic passage (STIRAP) scheme. We discuss the emergence of looped levels for an equal-slope Landau-Zener model. The Zener tunneling probability does not tend to zero in the adiabatic limit and shows pronounced oscillations as a function of the velocity of the parameter variation. Furthermore we generalize the STIRAP scheme for adiabatic coherent population transfer between atomic states to the nonlinear case. It is shown that STIRAP breaks down if the nonlinearity exceeds the detuning.