Light-matter Interaction Research Articles

Coherent coupling of localized surface plasmons and surface plasmons in borophene-based metamaterial

The strong coherent coupling in different electromagnetic modes can control the light-matter interaction more conveniently. Here, we theoretically researched the hybridization between the borophene surface plasmon (BSP) mode and the borophene localized surface plasmon (BLSP) mode in borophene grating structure. This coupling effect leads to the emergence of multiple hybrid modes. The absorption spectra of the system are investigated through finite difference time domain (FDTD) simulation and coupled oscillator model (COM). Results show that the coherent coupling of BSP and BLSP can be achieved by adjusting the carrier density of the borophene gratings. A Rabi splitting effect with frequency of 21.6 THz can be observed. Furthermore, we investigated the effects of geometric structural parameters, incident angle, and relaxation time on the correlated coupling spectra. Our work may deepen the understanding of light–matter interactions and provide a reference for borophene-based active photonic devices in the near-infrared region.

The Jaynes–Cummings model: 60 years and still counting

2023 marked the 60th anniversary of the Jaynes–Cummings model, a foundational model in quantum optics. Over the years, its importance has expanded beyond traditional light–matter interaction systems, such as cavity QED. This special issue presents a collection of articles that showcase the evolution of the model’s applications, blending traditional topics with contemporary developments.

Wide-Dynamic-Range Control of Quantum-Electrodynamic Electron Transfer Reactions in the Weak Coupling Regime.

Catalyzing reactions effectively by vacuum fluctuations of electromagnetic fields is a significant challenge within the realm of chemistry. As opposed to most studies based on vibrational strong coupling, we introduce an innovative catalytic mechanism driven by weakly coupled polaritonic fields. Through the amalgamation of macroscopic quantum electrodynamics (QED) principles with Marcus electron transfer (ET) theory, we predict that ET reaction rates can be precisely modulated across a wide dynamic range by controlling the size and structure of nanocavities. Compared to QED-driven radiative ET rates in free space, plasmonic cavities induce substantial rate enhancements spanning the range from 103- to 10-fold. By contrast, Fabry-Perot cavities engender rate suppression spanning the range from 10-2- to 10-1-fold. This work overcomes the necessity of using strong light-matter interactions in QED chemistry, opening up a new era of manipulating QED-based chemical reactions in a wide dynamic range.

Superluminality in parity-time symmetric Bragg gratings

Parity-time ( PT ) symmetric Bragg gratings (PTBGs) possess unique features compared to traditional ones. For example, the photonic bandgap of a PTBG can be modified and even closed when the PT symmetry evolves from an exact phase to a broken one, and the complex reflection coefficient of a PTBG is sensitive to the direction of incidence. In this article, we reveal how the superluminal effects of transmission behave following the modified band structure of PTBGs. The superluminality of the directionally sensitive reflection is also discussed. We then investigate the Hartman effect and argue that, to account for the superluminal effects in PTBGs, a directionally sensitive dwell time should be applied. This study offers unique insights into the mechanisms of superluminality and group delay of light in non-Hermitian open systems and contributes to the advancement of PTBGs, which can eventually become an indispensable platform for probing some of the exotic properties of optical wave phenomena and light–matter interactions.

The Unruh–DeWitt model and its joint interacting Hilbert space

In this work we make the connection between the Unruh–DeWitt (UDW) particle detector model applied to quantum field theory in curved spacetimes and the rigorous construction of the spin-boson (SB) model. With some modifications, we show that existing results about the existence of a SB ground state can be adapted to the UDW model. In the most relevant scenario involving massless scalar fields in (3+1)-dimensional globally hyperbolic spacetimes, where the UDW model describes a simplified model of light–matter interaction, we argue that common choices of the spacetime smearing functions regulate the ultraviolet behaviour of the model but can still exhibit infrared (IR) divergences. In particular, this implies the well-known expectation that the joint interacting Hilbert space of the model cannot be described by the tensor product of a two-dimensional complex Hilbert space and the Fock space of the vacuum representation. We discuss the conditions under which this problem does not arise and the relevance of the operator-algebraic approach for better understanding of particle detector models and their applications.Our work clarifies the connection between obstructions due to Haag’s theorem and IR bosons in the SB models, and paves the way for more rigorous study of entanglement and communication in the UDW framework involving multiple detectors.

A source of entangled photons based on a cavity-enhanced and strain-tuned GaAs quantum dot

A quantum-light source that delivers photons with a high brightness and a high degree of entanglement is fundamental for the development of efficient entanglement-based quantum-key distribution systems. Among all possible candidates, epitaxial quantum dots are currently emerging as one of the brightest sources of highly entangled photons. However, the optimization of both brightness and entanglement currently requires different technologies that are difficult to combine in a scalable manner. In this work, we overcome this challenge by developing a novel device consisting of a quantum dot embedded in a circular Bragg resonator, in turn, integrated onto a micromachined piezoelectric actuator. The resonator engineers the light-matter interaction to empower extraction efficiencies up to 0.69(4). Simultaneously, the actuator manipulates strain fields that tune the quantum dot for the generation of entangled photons with corrected fidelities to a maximally entangled state up to 0.96(1). This hybrid technology has the potential to overcome the limitations of the key rates that plague QD-based entangled sources for entanglement-based quantum key distribution and entanglement-based quantum networks.

Characterization of quantum dot-like emitters in programmable arrays of nanowrinkles of 1L-WSe2

When combined with nanostructured substrates, two-dimensional semiconductors can be engineered with strain to tailor light–matter interactions on the nanoscale. Recently, room-temperature nanoscale exciton localization with controllable wrinkling in 1L-WSe2 was achieved using arrays of gold nanocones. Here, the characterization of quantum dot-like states and single-photon emitters in the 1L-WSe2/nanocone system is reported. The nanocones induce a wide range of strains, and as a result, a diverse ensemble of narrowband, potential single-photon emitters is observed. The distribution of emitter energies reveals that most reside in two spectrally isolated bands, leaving a less populated intermediate band that is spectrally isolated from the ensembles. The spectral isolation is advantageous for high-purity quantum light emitters, and anti-bunched emission from one of these states is confirmed up to 25 K. Although the spatial distribution of strain is expected to influence the orientation of the transition dipoles of the emitters, multimodal emission polarization anisotropy and atomic force microscopy reveal that the macroscopic orientation of the wrinkles is not a good predictor of dipole orientation. Finally, the emission is found to change with thermal cycling from 4 to 290 K and back to 4 K, highlighting the need to control factors such as temperature-induced strain to enhance the robustness of this quantum emitter platform. The initial characterization here shows that controlled nanowrinkles of 1L-WSe2 generate quantum light in addition to uncovering potential challenges that need to be addressed for their adoption into quantum photonic technologies.

Phonon-mediated infrared plasmonic metamaterial emitters towards high-capacity multifunctional encoding and display

This study introduces what we believe is a novel approach to manipulating light in the mid-infrared spectrum through phonon-mediated metal-insulator-metal (MIM) cavities. Leveraging the unique interactions between resonantly excited electric and magnetic dipoles and phonons within silicon dioxide spacers, we have developed a technology different from traditional methods that rely on geometric modifications of nanostructures, offering a more versatile and effective means of tailoring light-matter interactions at the nanoscale. Our experimental results showcase the ability of these MIM cavities to perform multifunctional information encoding, display, and concealment with high precision. Notably, we encoded 13 distinct gray levels, surpassing previous capabilities in the long-wave infrared spectrum using metamaterial emitters. Furthermore, the incorporation of rotating nanorod structures enabled the encoding of grayscale patterns through polarization states, enhancing the potential for high-capacity information storage. The study also demonstrates the capability of these structures for subwavelength-resolution printing and near-diffraction-limit information encoding in the long-wave infrared band. We have successfully employed an innovative ink coating method, transparent in the long-wave infrared but opaque in the visible spectrum, to conceal encoded information, thereby adding a layer of security. In summary, the phonon-mediated infrared plasmonic metamaterial emitters presented in this work pave the way for future research in high-capacity information storage, anti-counterfeiting, and security technologies.

A comparative simulation study of light–matter coupling in 1D photonic crystals with 2D perovskite active layer

Light–matter interaction operating in the strong coupling regime offers wide prospects of applications going from nano-photonics to quantum communications. The most practical implementations are to embed the active matter into Fabry–Perot microcavities or photonic crystals. In this work we focus on the strong coupling of two-dimensional (2D) perovskite in 1D grating waveguide. We use rigorous coupled wave analysis to simulate electromagnetic wave confinement in the 1D waveguide. Various sets of waveguide geometrical parameters are examined to achieve the strong coupling regime for three different configurations of the active layer in the waveguide. To extract quantitatively the relevant physical parameters, such as strength of light–matter interaction, we develop a Hamiltonian formalism to reproduce results obtained by simulation. It is shown that the strongest interaction is to have the active layer inserted in the main slab of the waveguide. It is, however, still weaker by about 20% as compared to the use of Fabry–Perot microcavities.

Influence of Edges and Interlayer Electron-phonon Coupling in WS2/h-BN Heterostructure.

The semiconducting layered transition metal dichalcogenides (e.g., WS2) are excellent candidates for the realization of optoelectronic and nanophotonic applications on account of their band gap tunability, high binding energy and oscillator strength of the excitons, strong light-matter interaction, appreciable charge carrier mobility, and valleytronic properties. However, the photoluminescence (PL) emissions are reported to show a nonuniform spatial distribution, with the edges emitting features like defect-bound excitons and biexcitons at low temperatures in addition to the typical excitons and trions. The appearance of these additional PL features has been shown in the literature to have a strong dependence on the presence of S-vacancies and excess charge carriers. We demonstrate an enhancement of the defect-bound excitons and biexcitons by creating a heterostructure of WS2 with h-BN where the coupling between the charge carriers in WS2 with the polar phonons in h-BN governs the enhancement. Furthermore, we have performed a comprehensive resonant Raman study with varying polarization and magnetic field which not only confirms the presence of electron-phonon coupling in WS2/h-BN heterostructure, it further demonstrates a thermally induced differential resonance behavior with the excitonic level and the defect-induced midgap states (due to S-vacancies at the edge of WS2) exhibited by a dome-shaped behavior of the Raman intensities with temperature for the normal and defect-induced phonon modes. The defect-bound Raman modes exhibit maximum resonance at ∼240 K while normal Raman modes show at ∼280 K owing to a thermal variation of the electronic states.

Dynamic Ultrastrong Coupling in a 2 nm Gap Plasmonic Cavity at the Sub-Picosecond Scale.

Localized surface plasmon resonances (LSPRs) can enhance the electromagnetic fields on metallic nanostructures upon light illumination, providing an approach for manipulating light-matter interactions at the sub-wavelength scale. However, currently, there is no thorough investigation of the physical mechanism in the dynamic formation of the strongly coupled LSPRs on sub-5 nm plasmonic cavities at the sub-picosecond scale. In this work, through femtosecond broadband transient absorption spectroscopy, we reveal the dynamic ultrastrong coupling processes in a nanoparticle-in-trench (NPiT) structure containing 2 nm gap cavities, and demonstrate a coherent motional coupling between vibrating AuNPs and the nanogaps. We achieve a maximum Rabi splitting energy of ∼660 meV in the sub-picosecond hot-electron relaxation time scale under the resonant excitation of the nanogap cavity's LSPR, reaching the ultrastrong coupling regime. This leads to a change of global vibration modes for the 2 nm gap cavity, potentially related to the dynamical Casimir effect with nanogap resonators.

How near-field photon momentum drives unusual optical phenomena: opinion

This Opinion article discusses the fundamental role of the near-field photon momentum in processes of light scattering from nanometer-sized clusters including an intriguing case of self-assembled nanostructures that form a long-range translational order but local disorder. Systems exhibiting the so-called crystal-liquid duality enable greatly enhanced light-matter interactions due to the electron-photon momentum matching in the visible wavelength range. This work takes a historical perspective on the exploration of this phenomenon that has been somewhat overlooked by the scientific community and discusses recent advances in the fields of nonlocal photonics and optoelectronics.

Coherence-controlled chaotic soliton bunch

Controlling the coherence of chaotic soliton bunch holds the promise to explore novel light-matter interactions and manipulate dynamic events such as rogue waves. However, the coherence control of chaotic soliton bunch remains challenging, as there is a lack of dynamic equilibrium mechanism for stochastic soliton interactions. Here, we develop a strategy to effectively control the coherence of chaotic soliton bunch in a laser. We show that by introducing a lumped fourth-order-dispersion (FOD), the soliton oscillating tails can be formed and generate the potential barriers among the chaotic solitons. The repulsive force between neighboring solitons enabled by the potential barriers gives rise to an alleviation of the soliton fusion/annihilation from stochastic interactions, endowing the capability to control the coherence in chaotic soliton bunch. We envision that this result provides a promising test-bed for a variety of dynamical complexity science and brings new insights into the nonlinear behavior of chaotic laser sources.

Triple-enhanced Raman scattering sensor based on superhydrophobic/-philic microsphere platform and heating evaporation assisted for high-sensitivity detection

The ability to detect molecules in small volumes of highly diluted solutions is crucial for applications such as food quality and safety, environmental monitoring, biomedical diagnostics, and so on. The primary concern lies in the sensitivity and efficiency of detection technology. In this work, an ultra-sensitive surface-enhanced Raman scattering (SERS) detection strategy is presented, which is based on superhydrophobic/-philic microsphere SERS (SSM-SERS) platform and heating evaporation assisted for high-sensitivity detection. Relying on the heating-assisted evaporation, the evaporation efficiency of the droplet is increased by 378.5 times, and the deposition area after evaporation is reduced by 10.4 times, leading to the extremely high detection efficiency and further enrichment of the target molecules. When the microspheres array approaches the superhydrophobic/-philic (SH/SHL) substrate, the optical-plasmonic hybrid structure is formed, enhancing light-matter interactions and resulting in an improvement of the Raman signal. The optimized SERS sensor is capable of detecting Rhodamine 6 G (R6G) at the femtomolar level (10−16 M), with a sample volume of only 5 μL and an enhancement factor of 3.29 × 109. Considering the misuse of fish drugs, malachite green (MG) and methylene blue (MB) were chosen to validate the performance of SERS sensor. These findings highlight the consistent high sensitivity of the SERS sensor, offering valuable insights for applications in food safety and related fields.

Floquet analysis perspective of driven light–matter interaction models

In this paper, we analyze the harmonically driven Jaynes–Cummings and Lipkin–Meshkov–Glick models using both numerical integration of time-dependent Hamiltonians and Floquet theory. For a separation of time scales between the drive and intrinsic Rabi oscillations in the former model, the driving results in an effective periodic reversal of time. The corresponding Floquet Hamiltonian is a Wannier–Stark model, which can be analytically solved. Despite the chaotic nature of the driven Lipkin–Meshkov–Glick model, moderate system sizes can display qualitatively different behaviors under varying system parameters. Ergodicity arises in systems that are neither adiabatic nor diabatic, owing to repeated multi-level Landau–Zener transitions. Chaotic behavior, observed in slow driving, manifests as random jumps in the magnetization, suggesting potential utility as a random number generator. Furthermore, we discuss both models in terms of a Floquet Fock state lattice.

Optimized designs for micropillar cavity with simultaneously high quality factor and Gaussian far field at near-wavelength diameter

Micropillar cavities with small volumes and high quality factors (Q-factor) greatly enhance the light-matter interaction. Crucially, these cavities exhibit a near-Gaussian far-field pattern, making them highly suitable for efficiently coupling and manipulation of emitted photons. However, their miniaturization into near-wavelength scales is limited by diffraction, resulting in both Q-factor degradation and far-field emission divergence. Here, we propose a tapered micropillar cavity design that simultaneously achieves a high Q-factor (Q = 1.37 × 105) and near-Gaussian far-field emission at near-wavelength diameter (mode volume V m = 0.154λ3). Notably, its direct single-mode fiber coupling efficiency is 0.71, representing a remarkable 230 % improvement compared to traditional λ-micropillar cavities of the same diameter. Our results show prospects of ideal fiber-coupled platforms for cavity quantum electrodynamics experiments, particularly in the strong coupling regime.

Tunable single emitter-cavity coupling strength through waveguide-assisted energy quantum transfer

The emitter-cavity strong coupling manifests crucial significance for exploiting quantum technology, especially in the scale of individual emitters. However, due to the small light-matter interaction cross-section, the single emitter-cavity strong coupling has been limited by its harsh requirement on the quality factor of the cavity and the local density of optical states. Herein, we present a strategy termed waveguide-assisted energy quantum transfer (WEQT) to improve the single emitter-cavity coupling strength by extending the interaction cross-section. Multiple ancillary emitters are optically linked by a waveguide, providing an indirect coupling channel to transfer the energy quantum between target emitter and cavity. An enhancement factor of coupling strength g̃/g>10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\widetilde{g}/g > 10$$\\end{document} can be easily achieved, which dramatically release the rigorous design of cavity. As an extension of concept, we further show that the ancillae can be used as controlling bits for a photon gate, opening up new degrees of freedom in quantum manipulation.

Reversible modulation of superconductivity in thin-film NbSe2 via plasmon coupling

In recent years, lightwave has stood out as an ultrafast, non-contact control knob for developing compact superconducting circuitry. However, the modulation efficiency is limited by the low photoresponse of superconductors. Plasmons, with the advantages of strong light-matter interaction, present a promising route to overcome the limitations. Here we achieve effective modulation of superconductivity in thin-film NbSe2 via near-field coupling to plasmons in gold nanoparticles. Upon resonant plasmon excitation, the superconductivity of NbSe2 is substantially suppressed. The modulation factor exceeds 40% at a photon flux of 9.36 × 1013 s−1mm−2, and the effect is significantly diminished for thicker NbSe2 samples. Our observations can be theoretically interpreted by invoking the non-equilibrium electron distribution in NbSe2 driven by the plasmon-associated evanescent field. Finally, a reversible plasmon-driven superconducting switch is realized in this system. These findings highlight plasmonic tailoring of quantum states as an innovative strategy for superconducting electronics.

Unidirectional hyperbolic whispering-gallery phonon-polariton excitation in boron nitride nanotubes.

In two-dimensional (2D) hyperbolic materials, energy is directed into their deep subwavelength polaritonic modes through four narrow beams. Hyperbolic whispering-gallery mode nanocavity-confined phonon polaritons (PhPs) display a strongly enhanced light-matter interaction in the infrared regime. Particularly, the unidirectional phonon-polarization excitation in nanocavities has a potential application value in an on-chip integrated optical circuit design, efficient optical sensors, and enhanced spectral technology. Here, we explore the hyperbolic whispering-gallery mode PhPs on the cross section of a hexagonal BN nanotube (BNNT) and demonstrate that efficient unidirectional excitation can be achieved using a circularly polarized electric dipole, combining with optical spin-orbit coupling. Our results demonstrated that the undirectionality of the hyperbolic polariton propagation in a nanocavity can be conveniently achieved, independent of the structure symmetry of the nanocavity, providing potential applications in nanoscale light propagation, on-chip optical devices, and communication.

Laser-Induced Stress-Driven Nanoplate Jumping Visualized by Ultrafast Electron Microscopy.

Understanding laser-induced jumping has attracted great interest in nanomaterial launching and transfer but requires a high spatiotemporal resolution visualization. Here, we report a jumping dynamics of nanoplate driven by ultrafast laser-induced stress using time-resolved transmission electron microscopy. Single-shot imaging reveals a nondestructive launching of gold nanoplates in several nanoseconds after the pulsed femtosecond laser excitation. The temperature rise and acoustic vibration, derived from ultrafast electron crystallography with a picosecond time resolution, confirm the existence of a laser-induced elastic stress wave. The generation, propagation, and reflection of thermal stress waves are further clarified by atomic simulation. The nonequilibrium ultrafast laser heating produces a compressive stress wave within several picoseconds, constrained by the supporting substrate under nanoplate to provide thrust force. This compressive stress is subsequently reflected into tensile stress by the substrate, promoting the nanoplate to jump off the substrate. Furthermore, the uneven interface adhesion results in the jumping flip of nanoplates, as well as, diminished their jumping speed. This study unveils the jumping regime driven by impulsive laser-excited stress and offers understanding of light-matter interaction.