Photonic Modes Research Articles

High-performance silicon photonic single-sideband modulators for cold-atom interferometry.

The laser system is the most complex component of a light-pulse atom interferometer (LPAI), controlling frequencies and intensities of multiple laser beams to configure quantum gravity and inertial sensors. Its main functions include cold-atom generation, state preparation, state-selective detection, and generating a coherent two-photon process for the light-pulse sequence. To achieve substantial miniaturization and ruggedization, we integrate key laser system functions onto a photonic integrated circuit. Our study focuses on a high-performance silicon photonic suppressed-carrier single-sideband (SC-SSB) modulator at 1560 nanometers, capable of dynamic frequency shifting within the LPAI. By independently controlling radio frequency (RF) channels, we achieve 30-decibel carrier suppression and unprecedented 47.8-decibel sideband suppression at peak conversion efficiency of -6.846 decibels (20.7%). We investigate imbalances in both amplitudes and phases between the RF signals. Using this modulator, we demonstrate cold-atom generation, state-selective detection, and atom interferometer fringes to estimate gravitational acceleration, g ≈ 9.77 ± 0.01 meters per second squared, in a rubidium (87Rb) atom system.

Photon propagator for inflation in the general covariant gauge

Photon propagator for power-law inflation is considered in the general covariant gauges within the canonical quantization formalism. Photon mode functions in covariant gauges are considerably more complicated than their scalar counterparts, except for the special choice of the gauge-fixing parameter we call the simple covariant gauge. We explicitly construct the position space photon propagator in the simple covariant gauge, and find the result considerably more complicated than its scalar counterpart. This is because of the need for explicitly inverting the Laplace operator acting on the scalar propagator, which results in Appell’s fourth function. Our propagator correctly reproduces the de Sitter and flat space limits. We use this propagator to compute two simple observables: the off-coincident field strength-field strength correlator and the energy-momentum tensor, both of which yield consistent results. As a spinoff of our computation we also give the exact expression for the Coulomb gauge propagator in power-law inflation in arbitrary dimensions.

Symmetry breaking of bound states in the continuum in luminescence response of photonic crystal slabs with embedded Ge nanoislands

Bound states in the continuum (BIC) have attracted a great deal of attention in all-dielectric nanophotonics due to their ability to provide spectral features with a very high-quality factor. By definition, BIC cannot be observed in the far field because of the symmetry mismatch with the modes propagating in free space. Despite this, in systems with slightly reduced symmetry, the condition for BIC is lifted, which gives rise to the high-quality resonant features in their optical response. In particular, in photonic crystal slabs, which support the BIC states, the symmetry reduction allows modification of light propagation, reflection, or emission. In this work, using the photonic crystal slabs with embedded Ge nanoislands, we have shown the ability to control their light emission features by symmetry breaking. It was demonstrated that such symmetry breaking due to a change in the basis vectors of the photonic crystal unit cell or a change in the unit cell internal structure could provide independent control knobs to alter the spectral position of photonic crystal modes, their dispersion, and degeneracy. The obtained results reveal additional ways to manage the light emission of active media in photonic crystal slabs.

Entropy production rate and correlations in a cavity magnomechanical system

We present the irreversibility generated by a stationary cavity magnomechanical system composed of a yttrium iron garnet (YIG) sphere with a diameter of a few hundred micrometers inside a microwave cavity. In this system, the magnons, i.e., collective spin excitations in the sphere, are coupled to the cavity photon mode via magnetic dipole interaction and to the phonon mode via magnetostrictive force (optomechanical-like). We employ the quantum phase-space formulation of the entropy change to evaluate the steady-state entropy production rate and associated quantum correlation in the system. We find that the behavior of the entropy flow between the cavity photon mode and the phonon mode is determined by the magnon-photon coupling and the cavity photon dissipation rate. Interestingly, the entropy production rate can increase/decrease depending on the strength of the magnon-photon coupling and the detuning parameters. We further show that the amount of correlations between the magnon and phonon modes is linked to the irreversibility generated in the system for small magnon-photon coupling. Our results demonstrate the possibility of exploring irreversibility in driven magnon-based hybrid quantum systems and open a promising route for quantum thermal applications. Published by the American Physical Society 2024

Observation of Room Temperature Exchange Cavity Magnon‐Polaritons in Metallic Thin Films

AbstractCavity magnonics has become an intriguing field due to its potential to enable next‐generation technologies centered around controlling information exchange in hybrid resonant systems. Investigating the tunability of magnon‐photon coupling is key to advancing the field. Here, the observation of coupling between the first order magnon mode in a metallic thin film with a cavity photon mode is reported. An electromagnetic perturbation theory that takes account of perpendicular standing spin waves and their respective dissipation is utilized to estimate the coupling strength. The metallic thin film exhibits notably lower dissipation for the higher‐order magnon mode, which is not observed in a thin film magnetic insulator. As such, and given that metallic Kittel magnons typically exhibit lower coherence times than their insulator counterparts, the excitation and coupling to specific higher order modes could lengthen these times compared to previous observations, which may be useful for future integration into quantum devices.

Terminal-Matched Topological Photonic Substrate-Integrated Waveguides and Antennas for Microwave Systems.

In engineered photonic lattices, topological photonic (TP) modes present a promising avenue for designing waveguides with suppressed backscattering. However, the integration of the TP modes in electromagnetic systems has faced longstanding challenges. The primary obstacle is the insufficient development of high-efficiency coupling technologies between the TP modes and the conventional transmission modes. This dilemma leads to significant scattering at waveguide terminals when attempting to connect the TP waveguides with other waveguides. In this study, a topological photonic substrate-integrated waveguide (TPSIW) is proposed that can seamlessly integrate into traditional microstrip line systems. It successfully addresses the matching problem and demonstrates efficient coupling of both even and odd TP modes with the quasi-transverse electromagnetic modes of microstrip lines, resulting in minimal energy losses. In addition, topological leaky states are introduced through designed slots on the TPSIW top surface. These slots enable the creation of TP leaky-wave antennas with beam steering capabilities. A wireless link based on TPSIWs are further established that enables the transmission of distinct signals toward different directions. This work is an important step toward the integration of TP modes in microwave systems, unlocking the possibilities for the development of high-performance wireless devices.

Detection of entanglement by harnessing extracted work in magnomechanics

The connections between thermodynamics and quantum information processing are of paramount importance. Here, we address a bipartite entanglement via extracted work in a cavity magnomechanical system contained inside an yttrium iron garnet (YIG) sphere. The photons and magnons interact through an interaction between magnetic dipoles. A magnetostrictive interaction, analogous to radiation pressure, couple’s phonons and magnons. The extracted work was obtained through a device similar to the Szilárd engine. This engine operates by manipulating the photon–magnon as a bipartite quantum state. We employ logarithmic negativity to measure the amount of entanglement between photon and magnon modes in steady and dynamical states. We explore the extracted work, separable work, and maximum work for squeezed thermal states. We investigate the amount of work extracted from a bipartite quantum state, which can potentially determine the degree of entanglement present in that state. Numerical studies show that entanglement, as detected by the extracted work and quantified by logarithmic negativity, are in good agreement. We show the reduction of extracted work by a second measurement compared to a single measurement. Also, the efficiency of the Szilárd engine in steady and dynamical states is investigated. We hope this work is of paramount importance in quantum information processing.

Replica symmetry breaking in 1D Rayleigh scattering system: theory and validations

Spin glass theory, as a paradigm for describing disordered magnetic systems, constitutes a prominent subject of study within statistical physics. Replica symmetry breaking (RSB), as one of the pivotal concepts for the understanding of spin glass theory, means that under identical conditions, disordered systems can yield distinct states with nontrivial correlations. Random fiber laser (RFL) based on Rayleigh scattering (RS) is a complex disordered system, owing to the disorder and stochasticity of RS. In this work, for the first time, a precise theoretical model is elaborated for studying the photonic phase transition via the platform of RS-based RFL, in which we clearly reveal that, apart from the pump power, the photon phase variation in RFL is also an analogy to the temperature term in spin-glass phase transition, leading to a novel insight into the intrinsic mechanisms of photonic phase transition. In addition, based on this model and real-time high-fidelity detection spectral evolution, we theoretically predict and experimentally observe the mode-asymmetric characteristics of photonic phase transition in RS-based RFL. This finding contributes to a deeper understanding of the photonic RSB regime and the dynamics of RS-based RFL.

Polygon search algorithm for ultra-compact multifunctional integrated photonics design

Ultra-compact multifunctional integrated photonic modules have great practical significance to photonic integrated circuits (PICs). However, the design effect and efficiency of the existing mainstream inverse design algorithms are incompetent when designing these modules. We analyze their shortcomings in this task, and propose a new, to our knowledge, inverse design algorithm named polygon search (PS) algorithm to address these problems. We utilize the PS algorithm to design an integrated dual-channel mode-conversion-crossing waveguide module. This module integrates three functions: interconversion between TE0 and TE1, interconversion between TE0 and TE2, and channel crossing within only a 4 μm×4 μm footprint, and its performance is verified by experimental testing. It not only greatly reduces the total footprint of many PICs but also greatly improves their fabricating robustness. Furthermore, we propose a PS-designed mode mixer and a PS-designed bending waveguide, and connect them with the integrated modules to form a four-channel crossing-mode-division-multiplexing system. This system can provide multiple modes on the basis of channel crossing and transmit the output signal in the same direction in parallel within a single output waveguide, which significantly increases the communication bandwidth and decreases the footprint of PICs. At last, we demonstrate the effect and efficiency advantages of the PS algorithm over several mainstream inverse design algorithms by a comprehensive contrast experiment and explain these advantages in theory from several perspectives.

Room temperature photon-magnon coupling in YIG- electric field coupled resonator system

This study presents a planar hybrid system consisting of an electric-field-coupled resonator (ELCR) and yttrium iron garnet (YIG) film, designed to investigate the interaction between photons and magnons at room temperature. This hybrid system has been designed and simulated using the commercial electromagnetic full-wave simulator CST Microwave Studio. The phenomenon of anti-crossing between the photon mode of the ELCR and the magnon modes of the YIG was observed by analyzing the |S21|-versus-frequency spectrum under varying strengths of bias magnetic fields. We present a comprehensive theoretical framework that explains the observed anti-crossing effect resulting from photon-magnon coupling (PMC) and provide estimations for the strength of PMC (Δ). Additionally, the interaction between photons and magnons was manipulated through two distinct methods: by adjusting the thickness (tYIG) of the YIG film and by positioning the YIG films along the microstripline. For the ELCR (for tYIG = 25 μm), Δ comes to 58 MHz, while changing tYIG from 2 μm to 50 μm, enabling more precise control of the Δ parameter across the span of 17 MHz to 84 MHz. Similarly, the YIG positioning at a different location along the microstripline allowed manipulation of Δ from 5 to 50 MHz. The resultant PMC can be significantly tuned by 400% to 900% in a planar-geometry ELCR-YIG hybrid system. This research offers avenues for developing innovative hybrid systems that afford greater control over the magnitude of PMC in a planar configuration, representing a promising direction for future advancements in hybrid magnonic systems.

Resonance theory of vibrational strong coupling enhanced polariton chemistry and the role of photonic mode lifetime

Recent experiments demonstrate polaritons under the vibrational strong coupling (VSC) regime can modify chemical reactivity. Here, we present a complete theory of VSC-modified rate constants when coupling a single molecule to an optical cavity, where the role of photonic mode lifetime is understood. The analytic expression exhibits a sharp resonance behavior, where the maximum rate constant is reached when the cavity frequency matches the vibration frequency. The theory explains why VSC rate constant modification closely resembles the optical spectra of the vibration outside the cavity. Further, we discussed the temperature dependence of the VSC-modified rate constants. The analytic theory agrees well with the numerically exact hierarchical equations of motion (HEOM) simulations for all explored regimes. Finally, we discussed the resonance condition at the normal incidence when considering in-plane momentum inside a Fabry-Pérot cavity.

All-optical modulator with photonic topological insulator made of metallic quantum wells

Abstract All-optical modulators hold significant prospects for future information processing technologies for they are able to process optical signals without the electro-optical convertor which limits the achievable modulation bandwidth. However, owing to the hardly-controlled optical backscattering in the commonly-used device geometries and the weak optical nonlinearities of the conventional material systems, constructing an all-optical modulator with a large bandwidth and a deep modulation depth in an integration manner is still challenging. Here, we propose an approach to achieving an on-chip ultrafast all-optical modulator with ultra-high modulation efficiency and a small footprint by using photonic topological insulators (PTIs) made of metallic quantum wells (MQWs). Since PTIs have attracted significant attention because of their unidirectional propagating edge states, which mitigate optical backscattering caused by structural imperfections or defects. Meanwhile, MQWs have shown a large Kerr nonlinearity, facilitating the development of minimally sized nonlinear optical devices including all-optical modulators. The proposed photonic topological modulator shows a remarkable modulation depth of 15 dB with a substantial modulation bandwidth above THz in a tiny footprint of only 4 × 10 µm2, which manifests itself as one of the most compact optical modulators compared with the reported ones possessing a bandwidth above 100 GHz. Such a high-performance optical modulator could enable new functionalities in future optical communication and information processing systems.

Magneto-optical properties of a quantum dot array interacting with a far-infrared photon mode of a cylindrical cavity

Magneto-optical properties of a quantum dot array interacting with a far-infrared photon mode of a cylindrical cavity

Exhaustive review of acceleration strategies for Monte Carlo simulations in photon transit

Monte Carlo simulation techniques have become the quintessence and a pivotal nexus of inquiry in the realm of simulating photon movement within biological fabrics. Through the stochastic sampling of tissue archetypes delineated by explicit optical characteristics, Monte Carlo simulations possess the theoretical capacity to render unparalleled accuracy in the depiction of exceedingly intricate phenomena. Nonetheless, the quintessential challenge associated with Monte Carlo simulation methodologies resides in their extended computational duration, which significantly impedes the refinement of their precision. Consequently, this discourse is specifically dedicated to exploring innovations in strategies and technologies aimed at expediting Monte Carlo simulations. It delves into the foundational concepts of various acceleration tactics, evaluates these strategies concerning their speed, accuracy, and practicality, and amalgamates a comprehensive overview and critique of acceleration methodologies for Monte Carlo simulations. Ultimately, the discourse envisages prospective trajectories for the employment of Monte Carlo techniques within the domain of tissue optics.

Legume: A free implementation of the guided-mode expansion method for photonic crystal slabs

We describe legume, a free electromagnetic solver that implements the guided-mode expansion method for patterned multilayer waveguides, or photonic crystal slabs. legume has a built-in tool for automatic differentiation, which makes it suitable for the inverse design of photonic crystal structures with desired physical properties. Compared to a previous version of the method (M. Minkov et al., 2020 [12]), here we introduce several new features of the code, we discuss additional technical aspects of the method and its numerical implementation. The novel features that are treated in this paper include: (i) the separation of modes according to their mirror symmetry with respect to a vertical symmetry plane of the photonic structure, (ii) the problem of polarization mixing in coupling to far-field radiation modes, and (iii) the description of active two-dimensional layers through a suitably formulated radiation-matter coupling Hamiltonian, allowing to describe the physics of both weakly and strongly coupled exciton-photon modes, the latter leading to photonic crystal polariton eigenmodes. Detailed and direct comparisons with rigorous coupled-wave analysis simulations are used to test the accuracy of the method and the numerical efficiency of the code. These newly added features of the legume code significantly increase the prospective applications of guided-mode expansion, making it a very practical and versatile tool enabling the design of advanced photonic structures and the description of radiation-matter interaction. Program summaryProgram Title:legumeCPC Library link to program files:https://doi.org/10.17632/kf3cwknx4d.1Developer's repository link:https://github.com/fancompute/legumeLicensing provisions: MITProgramming language: PythonNature of problem: Dispersion and radiative losses of photonic eigenmodes in patterned multilayer waveguides/photonic crystal slabs/periodic metasurfaces. Interaction of photonic modes with exciton resonances leading to exciton-polaritons. Inverse design by optimization of the parameters.Solution method: Finite-basis expansion using a basis of guided modes of an effective homogeneous waveguide, perturbation theory to describe coupling with far-field radiation. Quantum theory of excitons, photons and their interaction to describe the occurrence of exciton-polaritons. Automatic differentiation via Autograd to implement inverse design. In this upgraded version of the legume code we implement symmetrization with respect to a vertical mirror plane and light-matter interaction for exciton-polaritons. Inverse design has been described previously, here we focus on the new features and applications of the code.

Positivity-causality competition: a road to ultimate EFT consistency constraints

Effective field theories (EFT) are strongly constrained by fundamental principles such as unitarity, locality, causality, and Lorentz invariance. In this paper, we consider the EFT of photons (or other U(1) gauge field) and compare different approaches to obtain bounds on its Wilson coefficients. We present an analytic derivation of the implications of unitarity (linear and non-linear positivity bounds) and compare these constraints with the requirement of causal propagation of the photon modes around non-trivial backgrounds generated by external sources. Within this setup, we find that the low energy causality condition can give complementary constraints to our analytic positivity bounds. In other words, simple analytic techniques can give strong constraints on the allowed region of the photon EFT parameters even when the positivity bounds are not numerically optimized.

Effective algorithms for calculation of quasi-probability distributions of bright “banana” states

Non-Gaussian quantum states, described by negative-valued Wigner functions, are important for both fundamental tests of quantum physics and for emerging quantum information technologies. One of the promising ways of generating a non-Gaussian state from a coherent one is the use of cubic (Kerr) optical nonlinearity, which produces the characteristic banana-like shape of the resulting quantum states. However, the Kerr effect is weak in highly transparent optical materials (dimensionless nonlinearity parameter Γ≲10−6). Therefore, a big number of the photons in the optical mode (n≳106) is necessary to generate an observable non-Gaussianity. In this case, the direct approach to calculation of the Wigner function becomes extremely computationally expensive. In this work, we develop quick algorithms for computing the Husimi and Wigner quasi-probability functions of these non-Gaussian states by means of the Kerr nonlinearity. This algorithm can be used for any realistic values of the photon numbers and the nonlinearity.

Site-Selective Plasmonic and Photonic Modulation of Galvanic Replacement Reaction between Silver Nanoprisms and Aqueous Chloroplatinate Ions

Site-Selective Plasmonic and Photonic Modulation of Galvanic Replacement Reaction between Silver Nanoprisms and Aqueous Chloroplatinate Ions

Direct Evidence of Ultrafast Energy Delocalization Between Optically Hybridized J‐Aggregates in a Strongly Coupled Microcavity

AbstractStrong coupling between light and matter in a microcavity can produce quasi‐particle states termed cavity‐polaritons. In cavity architectures containing more than one excitonic species, the photon mode can simultaneously couple to the different excitons, generating new ʻhybrid‐polaritonʼ states. It is demonstrated that such hybrid polariton states can energetically connect different molecular species, even when their intermolecular distance is much larger than the Förster transfer radius. Here, this mechanism is unveiled and observed in the time domain energy delocalization in a strongly coupled cavity containing two layers of donor and acceptor molecules, separated by an inert spacer layer of 2 µm thickness. 2D electronic spectroscopy is used, a technique that provides simultaneously high spectral and temporal resolution, to probe the dynamics of the energy flow processes following ultra‐fast excitation. It shows that energy is almost instantaneously delocalized among the polariton states, providing a direct connection between very highly separated donor and acceptor molecules. The results are of potential significance for light‐harvesting devices, optoelectronics, and bio‐photonic systems.

Back-focal plane scanning spectroscopy for investigating the optical dispersion of large-area two-dimensional photonic crystal fabricated by capillary force lithography

In this article, we introduce our custom-built back-focal plane (BFP) scanning spectroscopy to explore an angle-resolved optical dispersion in two-dimensional (2D) photonic crystal (PhC) constructed with hexagonal lattice of nano-scaled dielectric rods. We fabricated a uniformly large-area photonic crystal measuring 1 cm by 0.5 cm, featuring a polymer-based hexagonal lattice on a gold layer, using capillary force lithography. This precision enables the effective confinement of photonic modes, leading to enhanced optical interactions. We successfully map out the angle-resolved reflectance spectra by directly scanning BFP, revealing the structure's angle dependent optical response and providing insights into its iso-frequency contours. Our approach simplifies the exploration of advanced optical materials, highlighting the role of precise fabrication and measurement techniques in understanding and utilizing the optical properties of structured materials for various technological applications.