Optical Superlattice Research Articles

Thouless pumping and trapping of two-component gap solitons

We study Thouless pumping and arresting of gap solitons in a two-component Bose gas loaded into an optical superlattice. We show that, depending on the atomic interactions and chemical potentials, the two solitons can be simultaneously pumped or trapped, but we also identify regimes where one soliton is pumped and the other arrested. These behaviors can be understood by considering an effective model of the system based on a variational approach, which reveals that the soliton width is a suitable qualifier for the observed behaviors: solitons with a larger width get transported, while solitons with a smaller width get trapped. Since these widths can be controlled by tuning interactions, it should be possible to observe all behaviors experimentally. Published by the American Physical Society 2024

Optical manipulations without light forces: deep superlattice for trapping and rotation of impurity particles in a buffer gas

We propose a scheme to obtain a deep optical superlattice (OSL) for resonant impurity particles in a buffer gas. In contrast to the well-known traditional methods of forming optical lattices (supelattices) that are based on the gradient force of radiation pressure, the presented scheme is based on the effect of a light induced drift (LID) in interfering light waves. The principle of its operation is based on the conception of so-called rectified forces induced by interfering bichromatic optical fields, which was developed earlier in the theory of resonant radiation-pressure forces. In the scheme under consideration, a deep OSL (with a period much larger than the optical wavelength) is formed due to the action of the effective rectified force on atomic particles which is proportional to the difference between the frequencies of transport collisions of excited and unexcited particles with buffer gas atoms.

Magnetic transition of ytterbium atoms confined in optical superlattice with local ferromagnetic interaction

We used the density matrix renormalization group to study the ground state of ytterbium atoms (171Yb) for the Hund lattice model, where the delocalized atoms are confined in a onc-dimensional optical superlattice and his number is one third of the lattice sites. We found a paramagnetic-ferromagnetic quantum phase transition for any value of the potential strength. The local critical ferromagnetic coupling decreases as the superlattice potential increases.

Quadripartite quantum steering generated by single-pass cascaded nonlinear processes

Quantum steering has become an important resource for quantum information due to its unique asymmetry. In this paper, quadripartite quantum steering generated by single-pass nondegenerate optical parametric amplification cascaded with a sum-frequency process is investigated. Firstly, an idler beam is produced by a different-frequency process between pump and signal. Secondly, a sum-frequency beam is generated by a cascaded sum-frequency process between idler beam and pump in the same optical superlattice. Quadripartite quantum steering among pump, signal, idler and sum-frequency beams is demonstrated based on the criterion for multipartite quantum steering. The influences of nonlinear coupling coefficients κ, dimensionless propagation length ξ, and the initial values of pump and signal on the variation characteristic of the quadripartite steering are also investigated. The results indicate that slightly larger nonlinear coupling coefficients of cascaded nonlinear processes and weaker signals can achieve better quadripartite quantum steering. This simple quadripartite quantum steering preparation scheme does not require a resonant cavity and is easier to implement experimentally, with potential applications in quantum communication and computing.

The generation of genuine quadripartite Einstein–Podolsky–Rosen steering in an optical superlattice

Einstein–Podolsky–Rosen (EPR) steering is a quantum effect based on quantum entanglement and it is the key resource for building quantum networks because of its useful properties. Based on the criterion for genuine multipartite EPR steering, the genuine quadripartite EPR steering is confirmed and it can be generated by a spontaneous parametric down-conversion cascaded process with two sum-frequency generations in an optical superlattice. This occurs either below the oscillation threshold and without oscillation threshold. The influence of the parameters of cascaded nonlinear process on the quadripartite EPR steering among signal, idler, and two sum-frequency beams are also discussed. Choosing appropriate nonlinear parameters can achieve good quadripartite quantum steering. This scheme of the generation of genuine quadripartite EPR steering has potential applications in quantum communication and computing.

Understanding the coupling between MIM cavities due to single and double Tamm plasmon polaritons

The interplay between light and matter plays a crucial role in various applications, ranging from sensor technologies to integrated optoelectronic architectures. In this contribution, a systematic numerical study is made over the symmetry role of the 1D photonic structures (PhSs) containing a low number of slabs embedded in thin metal layers, in order to find the adequate conditions to enhance the quality factor of resonances and energy confinement in the subwavelength scale. We show the existence of single and double Tamm plasmon polaritons (TPPs) states according to the symmetry of the PhS, which allow to tune weak and strong coupling regimes with Metal–Insulator–Metal (MIM) platforms combined in a unique MIM-PhS-MIM structure. We found that while weak coupling is observable between MIM and PhS states at the PhS cavity mode wavelengths, strong coupling among the 2 MIMs and the PhS is obtained only at the TPP resonance wavelengths, exhibited by anti-crossing splittings at adequate insulator thicknesses. We found that for the double Tamm plasmon polaritons, the energy splitting can reach up to 134 meV, unlike the single TPPs where the maximum energy splitting is on the order of 50 meV. The degree of coupling was explained by the implementation of a variational method that exploits the analogy the optical superlattice herein proposed and an analogous superlattice quantum well. This article shows that TPP resonances are responsible for the coherent coupling between the two MIMs placed at a long distance given by the PhSs. Thus, these platforms provide an interesting and experimentally accessible route for the coupling of emitters in optoelectronic devices.

Scalable Multipartite Entanglement Created by Spin Exchange in an Optical Lattice.

Ultracold atoms in optical lattices form a competitive candidate for quantum computation owing to the excellent coherence properties, the highly parallel operations over spins, and the ultralow entropy achieved in qubit arrays. For this, a massive number of parallel entangled atom pairs have been realized in superlattices. However, the more formidable challenge is to scale up and detect multipartite entanglement, the basic resource for quantum computation, due to the lack of manipulations over local atomic spins in retroreflected bichromatic superlattices. In this Letter, we realize the functional building blocks in quantum-gate-based architecture by developing a cross-angle spin-dependent optical superlattice for implementing layers of quantum gates over moderately separated atoms incorporated with a quantum gas microscope for single-atom manipulation and detection. Bell states with a fidelity of 95.6(5)% and a lifetime of 2.20±0.13 s are prepared in parallel, and then connected to multipartite entangled states of one-dimensional ten-atom chains and two-dimensional plaquettes of 2×4 atoms. The multipartite entanglement is further verified with full bipartite nonseparability criteria. This offers a new platform toward scalable quantum computation and simulation.

A hybrid mechanism of 3D optical trapping of particles immersed in a cold buffer gas

A novel mechanism of the formation of a deep optical superlattice (OSL) for three-dimensional (3D) trapping of resonant impurity atoms immersed in a transparent cold buffer gas is proposed and investigated theoretically. This mechanism is associated with the joint action of two factors of different physical nature: rectification effect of the gradient force of light pressure and effect of the light induced drift (LID) of atoms (a consequence of the difference in gas-kinetic cross sections of excited and unexcited atoms). Such a situation can be realised when a gas mixture is irradiated by a bichromatic combined light beam which is a special coaxial superposition of cosine-Gaussian optical beams. Here, the RcGF creates a periodic 1D array of deep potential wells (OSL) along the beam axes, and an effective force, causing LID, pulls resonant particles into the combined light beam and provides their transverse (with respect to the beam axes) confinement in OSL. As a result, there can occur a giant accumulation of impurity particles in the OSL cells, accompanied by a strong spatial particle localization far away from the walls of the reservoir, in which the gas mixture is located.

Tunable Low-Threshold Optical Bistability in Optical Tamm Plasmon Superlattices

We propose a scheme to obtain tunable low-threshold optical bistability of reflected beams in optical Tamm plasmon superlattices (TPS). The low-threshold optical bistability is triggered due to the strong third-order non-linearity of graphene and the local field enhancement in the TPS. Our results show that the optical Tamm plasmon superlattices have the ability to lower the bistable threshold even further than the single optical Tamm state. The results show that the hysteresis behavior and optical bistability threshold can be continuously adjusted by changing the applied voltage and the number of graphene layers (N ≤ 4). In particular, the optical bistability in the TPS is affected by the incident angle. Our results introduce a new possible route for low threshold optical bistability in the THz range and provide a new method in the field of all-optical switching applications.

Exploring interacting topological insulator in the extended Su-Schrieffer-Heeger model

Exploring topological phases in interacting systems is a challenging task. We investigate many-body topological physics of interacting fermions in an extended Su-Schrieffer-Heeger (SSH) model, which extends the two sublattices of SSH model into four sublattices and thus is dubbed SSH4 model, based on the density-matrix renormalization-group numerical method. The interaction-driven phase transition from topological insulator to charge density wave (CDW) phase can be identified by analyzing the variations of entanglement spectrum, entanglement entropies, energy gaps, CDW order parameter, and fidelity. We map the global phase diagram of the many-body ground state, which contains nontrivial topological insulator, trivial insulator and CDW phases, respectively. In contrast to interacting SSH model, in which the phase transitions to the CDW phase are argued to be first-order phase transitions, the phase transitions between the CDW phase and topologically trivial/nontrivial phases are shown to be continuous phase transitions. Finally, we {also} show the phase diagram of interacting spinful SSH4 model, where the attractive (repulsive) on-site spin interaction amplifies (suppresses) the CDW phase. The models analyzed here can be implemented with ultracold atoms on optical superlattices.

Mapping atomic trapping in an optical superlattice onto the libration of a planar rotor in electric fields

We show that two seemingly unrelated problems—the trapping of an atom in an optical superlattice (OSL) and the libration of a planar rigid rotor in combined electric and optical fields (PR) – have isomorphic Hamiltonians. Formed by the interference of optical lattices whose spatial periods differ by a factor of two, OSL gives rise to a periodic potential that acts on atomic translation via the AC Stark effect. The PR system, also known as the generalized planar pendulum, is realized by subjecting a planar rigid rotor to combined orienting and aligning interactions due to the coupling of the rotor’s permanent and induced electric dipole moments to the combined fields. The PR system belongs to the class of conditionally quasi-exactly solvable problems and exhibits intriguing spectral properties that have been established in our previous work Becker et al (2017 Eur. Phys. J. D 71 149). Herein, we make use of both the PR OSL mapping and the quasi-exact solvability of the PR system to treat ultracold atoms in an OSL as a semifinite-gap system. The band structure of this system follows from the eigenenergies and their genuine and avoided crossings obtained previously for the PR system as solutions of the Whittaker-Hill equation. These solutions characterize both the squeezing and the tunneling of atoms trapped in an OSL and pave the way to unraveling their dynamics in analytic form. Furthermore, the PR OSL mapping makes it possible to establish correspondence between concepts developed for the two eigenproblems individually, such as localization on the one hand and orientation/alignment on the other.

Multifunctional Nanostructures with Controllable Band Gap Giving Highly Stable Infrared Emissivity for Smart Thermal Management.

Thermal control is essential to guarantee the optimal performance of most advanced electronic devices or systems. In space, orbital satellites face the issues of high thermal gradients, heating, and different thermal loads mediated by differential illumination from the Sun. Todaýs state-of-the-art thermal control systems provide protection; however, they are bulky and restrict the mass and power budgets for payloads. Here, we develop a lightweight optical superlattice nanobarrier structure to provide a smart thermal control solution. The structure consists of a moisture and outgassing physical barrier (MOB) coupled with atomic oxygen (AO)-UV protection functionality. The nanobarrier exhibits transmission and reflection of light by controlling the optical gap of individual layers to enable high infrared emissivity and variable solar absorptivity (minimum ΔαS = 0.30) across other wavelengths. The multifunctional coating can be applied to heat-sensitive substrates by means of a bespoke room-temperature process. We demonstrate enhanced stability, energy-harvesting capability, and power savings by facilitating the radiation cooling and facility for active self-reconfiguration in orbit. In this way, the reduction of the operating temperature from ∼120 to ∼60 °C on space-qualified and nonmechanically controlled composite structures is also demonstrated.

Simultaneous electro-optic spectral switching and Q switching in a dual-wavelength Nd:YVO4 laser based on an aperiodic optical superlattice lithium niobate.

We report the demonstration of an electro-optic (EO) switchable dual-wavelength (1064- and 1342-nm) Nd:YVO4 laser based on an aperiodically poled lithium niobate (APPLN) chip whose domain structure is designed using aperiodic optical superlattice (AOS) technology. The APPLN works as a wavelength-dependent EO polarization-state controller in the polarization-dependent laser gain system to enable switching among multiple laser spectra simply by voltage control. When the APPLN device is driven by a voltage-pulse train modulating between a VHQ (in which target laser lines obtain gain) and a VLQ (in which laser lines are gain suppressed), the unique laser system can produce Q-switched laser pulses at dual wavelengths 1064 and 1342 nm, single wavelength 1064 nm, and single wavelength 1342 nm, as well as their non-phase-matched sum-frequency and second-harmonic generations at VHQ = 0, 267, and 895 V, respectively. A laser can benefit from such a novel, to the best of our knowledge, simultaneous EO spectral switching and Q switching mechanisms to increase its processing speed and multiplexity for versatile applications.

Tuning the Topological θ -Angle in Cold-Atom Quantum Simulators of Gauge Theories

The topological θ-angle in gauge theories engenders a series of fundamental phenomena, including violations of charge-parity (CP) symmetry, dynamical topological transitions, and confinement-deconfinement transitions. At the same time, it poses major challenges for theoretical studies, as it implies a sign problem in numerical simulations. Analog quantum simulators open the promising prospect of treating quantum many-body systems with such topological terms, but, contrary to their digital counterparts, they have not yet demonstrated the capacity to control the θ-angle. Here, we demonstrate how a tunable topological θ-term can be added to a prototype theory with U(1) gauge symmetry, a discretized version of quantum electrodynamics in one spatial dimension. As we show, the model can be realized experimentally in a single-species Bose-Hubbard model in an optical superlattice with three different spatial periods, thus requiring only standard experimental resources. Through numerical calculations obtained from the time-dependent density-matrix renormalization group method and exact diagonalization, we benchmark the model system, and illustrate how salient effects due to the θ-term can be observed. These include charge confinement, the weakening of quantum many-body scarring, as well as the disappearance of Coleman’s phase transition due to explicit breaking of CP symmetry. This work opens the door towards studying the rich physics of topological gauge-theory terms in large-scale cold-atom quantum simulators.4 MoreReceived 15 April 2022Revised 19 September 2022Accepted 26 September 2022DOI:https://doi.org/10.1103/PRXQuantum.3.040316Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasColor confinementColor deconfinementConfinementQuantum simulationPhysical Systems1-dimensional systemsBose gasesTechniquesBose-Hubbard modelDensity matrix renormalization groupExact diagonalizationGauge symmetriesLattice gauge theoryPerturbation theoryAtomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Flexible dual-wavelength second-harmonic generation in nested quasi-periodic optical superlattice

Flexible dual-wavelength second-harmonic generation in nested quasi-periodic optical superlattice

Ferroelectric Domain Reversal Dynamics in LiNbO3 Optical Superlattice Investigated with a Real‐Time Monitoring System (Small 32/2022)

Ferroelectric Domain Reversal Dynamics in LiNbO₃ Optical Superlattice Investigated with a Real‐Time Monitoring System (Small 32/2022)

Opto-thermophoretic superlattice for atoms

We propose and study a dissipative optical superlattice for manipulation of resonant particles (atoms, ions and similar ones) located in a transparent buffer gas. Its working principle is based on the simultaneous effect of a longitudinal rectified gradient force and a transverse thermophoretic force in the field of collinear superposition of bichromatic cosine-Gaussian laser beams. As a result, there occurs a strong periodic stratification of the gas manifested in the accumulation and sharp localization of the resonant particles at the nodes of the superlattice and their cooling. Moreover, in the case of linearly polarized light beams, there appear circulating currents of the resonant particles (the so-called Brownian vortices) in the gas. Unlike the traditional dissipative optical lattices, in the superlattice under consideration, transverse particle confinement is implemented only due to the light-induced thermophoretic force, associated with the finiteness of the effective radius of the light beams.

Ferroelectric Domain Reversal Dynamics in LiNbO3 Optical Superlattice Investigated with a Real-Time Monitoring System.

The optical superlattice structure derived from a periodic poling process endows ferroelectric crystals with tunable optical property regulation, which has become one of the most efficient strategies for fabricating high-efficiency optical devices. Achieving a precise superlattice structure has been the main barrier for preparation of specific optical applications due to the unclear dynamics of domain structure regulation. Herein, a real-time monitoring system for the in situ observation of periodic poling of lithium niobate is established to investigate ferroelectric domain reversal dynamics. The formation of reversed domain nuclei, growth, and expansion of the domain are monitored, which is highly related to domain growth dynamics. The nucleation and growth of domain are discussed combined with the monition of domain reversal and the variation of local electric field distribution along with finite element analysis. An electrode configuration with multiholes is proposed to use the local electric field more efficiently and controllably, which could achieve a higher domain nucleus density with high uniformity. Two-mm-thick periodically poled LiNbO3 crystals with high quality are achieved. A nonlinear light conversion from 1064.2 to 3402.4nm is realized by the single-resonance optical parameter oscillator with a nonlinear optical efficiency up to 26.2%.

Asymmetric Quantum Steering Generated by Triple-Photon Down-Conversion Process With Injected Signals

Asymmetric quantum steering generated by the triple-photon down-conversion process in an injected signal optical cavity is investigated. The triple-photon down-conversion process can be realized in an optical superlattice by quasi-phase-matching technology. Asymmetric quantum steering can be obtained in this triple-photon down-conversion process. The direction of asymmetric quantum steering can be controlled by adjusting the parameters of the nonlinear process. The generation of asymmetric quantum steering in the present scheme has potential applications in quantum secret sharing and quantum networks.

Generalized Aubry–André–Harper Models in Optical Superlattices

Ultracold atoms trapped in optical superlattices provide a simple platform for realizing the seminal Aubry–André–Harper (AAH) model. However, this model ignores the periodic modulations on the nearest-neighbor hoppings. We establish a generalized AAH model by which an optical superlattice system can be approximately described when V 1 ≫ V 2, with periodic modulations on both on-site energies and nearest-neighbor hoppings. This model supports much richer topological properties absent in the standard AAH model. Specifically, by calculating the Chern numbers and topological edge states, we show that the generalized AAH model possesses multifarious topological phases and topological phase transitions, unlike the standard AAH model supporting only a single topological phase. Our findings can uncover more opportunities for using optical superlattices to study topological and localization physics.