Topological defects in two-dimensional (2D) and three-dimensional topological materials can induce exotic phenomena, such as protected localized modes. The introduction of synthetic dimensions further enables the exploration of such effects in higher-dimensional systems. Recent studies reveal that a 2D photonic crystal with 2D synthetic translation space ($\mathrm{\Delta }x,\mathrm{\Delta }y$) supports gapless dislocation modes, protected by the second Chern number of the four-dimensional pseudomomentum space $(k_x,\mathrm{\Delta }x,k_y,\mathrm{\Delta }y)$. However, the complexity of the dislocation lattice and the unclear mode-formation mechanism hinder applications in wave devices. To simplify the structure and clarify the physics, we discretize the lattice into four sectors. So that the sectored dislocation lattice can be viewed as the interface between two one-dimensional (1D) edge systems with edge states. The $(k_y,\mathrm{\Delta }y)$ subspace topology staggers the edge bands of two 1D edge systems, yielding a common edge gap with differing band counts below it, while the $(k_x,\mathrm{\Delta }x)$ subspace topology ensures a first Chern number of $-1$ to each band. Their joint contribution guarantees a gapless dislocation band spanning the common edge gap, protected by the second Chern number. Based on this mechanism, we propose an easy-to-integrate topological wavelength-selective component using sectored translation scheme. This work elucidates the formation mechanism of gapless dislocation modes and expands the design paradigm for topological functional systems in synthetic translation dimensions.

An arrayed silicon-based nanotip optical antenna (NOA) architecture for guiding efficient near-infrared imaging detection is proposed. The NOA can be effectively actuated based on the geometric field enhancement due to the tip effect and the patterned redistribution of the surface net charges, leading to a highly localized electron accumulation at the tips, a strong field electron emission away from the tips, and continuously visible cathodoluminescence. The photoelectronic response measurements reveal an effective spectral transformation from the initial infrared region to the visible band with a central wavelength of 544 nm. Spectral characterized analyses exhibit a strong electric-field amplitude gain of 84.77 at 1000 nm and an ultralow radiation transmittance of less than 2% across a broad wavelength range from 400 nm to 14 µm. The measured output electric signal is sensitive to the incident radiation, reaching a high value of 186.05 mV under illumination of 2.47 W. The photoelectric measurements indicate an intense output voltage signal with a nanosecond-level time interval between adjacent output peaks and a shorter duration of a single peak in both the visible and near-infrared regions. The point-spread function of the emitted light beams away from a single nanotip presents a remarkably strengthened and expanded nanofocusing, which means a notable arrayed light-field enhancement in the $\mathrm{Si}$-based NOA configuration. A nanotip-based imaging detector (NID) architecture has been effectively constructed by closely coupling a common complementary metal-oxide semiconductor sensor array with a compact $\mathrm{Si}$-based NOA chip. An obvious improvement in the imaging performance has been realized using the NID construction with a wider radiation response range.

Photonic integrated Brillouin lasers have emerged as a key tool to realize a wide range of precision applications, including atomic time keeping, low-noise microwave-signal generation, fiber and quantum sensing, and ultrahigh capacity coherent communications. While Brillouin lasers routinely achieve sub-Hz instantaneous linewidths, many of these applications also require exceptional frequency stability and high-power single-mode emission. A recent demonstration showed that extending the resonator length increases the laser power while simultaneously improving the frequency stability through suppression of low-frequency thermorefractive noise. However, as the resonator length scales to larger size, multiple optical resonances can be found within the Brillouin gain bandwidth, greatly complicating the laser dynamics and extending beyond the validity of existing coupled-mode Brillouin laser models. Given the potential to scale lasers of this type to watt-level output powers at sub-mHz linewidths, a theoretical model describing this physics is needed to provide key insights into their performance. Here, we develop a coupled-mode theory of integrated large mode volume Brillouin lasers, accounting for multiple cavity modes with the potential to lase within the gain bandwidth. We obtain expressions for the steady-state dynamics, spontaneous spectrum, relative intensity noise, and frequency noise. Our analysis reveals that the broad gain bandwidth results in atypical Brillouin dynamics, giving rise to distinct features in the noise spectra, and consequently modifications of the standard, single-mode fundamental linewidth of Brillouin lasers. Additionally, these features may be used for a variety of tangential applications, such as phonon spectroscopy or quality-factor enhancement. Furthermore, we find that the linewidth can be significantly impacted by transferred RIN from the external pump in Brillouin lasers that lack ideal phase matching.

Epsilon-near-zero (ENZ) thin films facilitate strong light-matter interactions with a widespread impact in nonlinear, quantum and thermal photonics. Here, we extend the scope of thin-film ENZ modes by elucidating the generalized polaritonic modes emerging from anisotropy and near-zero permittivity. Through a theoretical investigation of generalized ENZ polaritons on silicon carbide metasurfaces, we reveal a complex polaritonic landscape, consisting of an eight-region phase diagram. We show that the complex interplay between material properties and geometry changes the nature of the modes, and we clarify when ENZ modes with closed and open isofrequency curves can be observed, and how they coexist with surface phonon polaritons and hyperbolic modes. The associated photonic topological transitions are accompanied by phase velocity sign reversals and induce dramatic modifications of near-field profiles and Purcell enhancement factors. Our work merges insights from anisotropic and ENZ effects, enabling enhanced control over polariton behavior with broad implications for subwavelength optics, material design, nonlinear effects, thermal emission, and quantum technologies.

Optical Schrödinger cat states are non-Gaussian states with applications in quantum technologies, such as for building error-correcting states in quantum computing. Nevertheless, the efficient generation of high-fidelity optical Schrödinger cat states is an outstanding problem in quantum optics. Here we propose using squeezed superpositions of zero and two photons, $|\theta ⟩=\cos (\theta /2)|0⟩+\sin (\theta /2)|2⟩$, as ingredients for protocols to efficiently generate high-fidelity cat states. We present a protocol using linear optics with success probability $P\gtrsim 50\mathrm{\%}$ that can generate cat states of size $|\alpha {|}^2=5$ with fidelity $F>0.99$. The protocol relies only on detecting single photons and is remarkably tolerant of loss, with 2% detection loss still achieving $F>0.98$ for cat states with $|\alpha {|}^2=5$. We also show that squeezed $\theta$ states are ideal candidates for nonlinear photon subtraction using a two-level system with near-deterministic success probability and fidelity $F>0.98$ for cat states of size $|\alpha {|}^2=5$. Schemes for generating $\theta$ states using quantum emitters are also presented. Our protocols can be implemented with current state-of-the-art quantum optics experiments.

Non-Hermitian photonic systems, where gain, loss, and nonlinear interactions interplay, offer a fertile ground for realizing complex dynamical behavior such as broken reciprocity, self-oscillations, and excitable dynamics. Here, we report experimental observations of phase-controlled hysteresis in a nonlinear, non-Hermitian silicon microring resonator with dynamically tunable coupling between counterpropagating modes. By integrating independent thermal phase shifters, we modulate the intermodal feedback phase in real time and access regimes with different energy stored in the cavity, allowing us to investigate conditions governed by thermo-optic and free-carrier nonlinearities. We observe non-Markovian memory effects in the form of path-dependent phase trajectories: forward and reverse phase sweeps lead to distinct steady or oscillatory states, despite identical boundary conditions. This hysteresis is underpinned by a nonlocal bifurcation, where the system transitions from a stable fixed point to a saddle-node annihilation, to finally ending in a distant limit cycle. Our results demonstrate coherent phase control as a tool for accessing previously unseen bifurcation structures in photonics, and they establish a scalable platform for exploring neuromorphic dynamics beyond classical excitability.

A minimalistic setup comprising a single homogeneous material, in bulk or two-dimensional form, is examined with respect to its ability to absorb visible light. The performance is assessed in terms of the Rozanov bound expressing the bandwidth-thickness balance, the average absorption indicating the broadband efficiency, and the minimal absorbance characterizing the self-camouflage ability. The materials used include ordinary lossy dielectric media, substances with ideal dispersion yielding perfect absorption across the whole visible spectrum, as well as their causal counterparts. The reported results show the optimal operating conditions of such a simple design, which may serve as a key component in absorption-based applications ranging from energy harvesting and medical imaging to photodetection and radar target concealment.

Rydberg atoms, due to their large polarizabilities and strong transition dipole moments, have been utilized as sensitive electric field sensors. While their ability to detect modulated signals has been previously demonstrated, these studies have largely been limited to laboratory-generated signals tailored specifically to atomic detection. Here, we extend the practical applicability of Rydberg sensors by demonstrating the reception of real-world frequency-modulated (FM) audio transmissions using a consumer-grade handheld two-way radio operating in the UHF band. Detection is based on the ac Stark shift induced by the radio signal in a Rydberg atomic vapor, with demodulation performed using an offset local oscillator and lock-in amplification. We successfully demodulate speech signals and evaluate the audio spectral response and reception range. We show that all consumer-accessible radio channels can be simultaneously detected, and demonstrate simultaneous reception of two neighboring channels with at least 53 dB of isolation. This work underscores the potential of Rydberg atom-based receivers for practical, real-world FM signal detection.

Semiconductor membranes are widely used in research fields that target medical, biological, environmental, and optical applications. Often such membranes derive their functionality from a nanopatterning, which challenges the determination of their optical, electronic, mechanical, and thermal properties. In this work, we demonstrate the noninvasive, all-optical thermal characterization of approximately-800-nm-thick and approximately-150-$\text{μ}\mathrm{m}$-wide membranes that consist mainly of wurtzite GaN and a stack of ${\mathrm{In}}_{0.15}{\mathrm{Ga}}_{0.85}\mathrm{N}$ quantum wells as a built-in light source. Because of their application in photonics, e.g., for vertical-cavity surface-emitting lasers, such photonic membranes are bright light emitters, which challenges their thermal characterization by optical means. We combine top-view two-laser Raman thermometry (2LRT) with time-resolved photoluminescence spectroscopy to extract the in-plane thermal conductivity ${\kappa }_{\text{in~plane}}$ of these membranes, which represents a notable difference from previous studies on epitaxial GaN films. Thus, we can disentangle the entire laser-induced power balance. Thermal imaging by Raman spectroscopy yields ${\kappa }_{\text{in plane}}={165}_{-14}^{+16}\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ for the best membrane. This result compares well with ${\kappa }_{\text{in plane}}=177\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ obtained by ab initio simulations based on a solution of the linearized phonon Boltzmann transport equation, including three- and four-phonon scattering, as well as phonon-isotope and phonon-boundary scattering. Furthermore, we study how ${\kappa }_{\text{in plane}}$ is affected by a roughening of the membrane’s back side and additional semiconductor layers. For the membrane with the roughest back side, we observe a reduction of ${\kappa }_{\text{in plane}}$ by almost 40%, which is accompanied by an anisotropy of ${\kappa }_{\text{in plane}}$ due to etch channel formation. Thanks to the 2LRT approach, such variations and anisotropies of ${\kappa }_{\text{in plane}}$ become accessible to the experimentalist via highly spatially resolved temperature maps.

Graphene is a promising material for nonlinear THz applications due to its high third-order susceptibility and tunable optical properties. Its strong nonlinear response, driven by free-carrier thermodynamics, facilitates efficient third-harmonic generation (THG), which can be further enhanced using resonant metasurfaces and plasmonic structures. In this study, we use a platform designed to boost THG at THz frequencies by integrating graphene ribbons into the interface between topological photonic crystals. To accurately capture the temperature dependence of the nonlinear optical response, we perform coupled simulations to model graphene’s optical and thermodynamic responses under THz photoexcitation, incorporating photoinduced hot-carrier effects within a multiphysics computational framework. This approach unveils the influence of carrier heating on THG, providing a more accurate description of nonlinear THz processes and revealing previously overlooked mechanisms of third-order conductivity modulation. We show that the elevated carrier temperature promotes high conversion efficiencies at moderate input intensities, within a design that operates in both reflection and transmission modes for advanced ultrafast optoelectronic devices in the THz regime.

Quantum key distribution (QKD) can distribute secret keys between two parties over a long distance. In practical applications, the demand for multiplexing QKD and conventional data communication through wavelength-division multiplexing (WDM) in the same fiber is increasing. However, the in-band noise that is difficult to filter out through experimental methods has become a key factor limiting the performance of WDM-QKD systems. In this work, we establish a practical decoy-state WDM-QKD model with advantage distillation (AD). We theoretically investigate the enhancement of AD technology on WDM-QKD systems and experimentally verify it. When the classical launch power is fixed at 8.6 dBm, the transmission distance can be extended by 80.3 km. When the classical received power is fixed at $-27$ dBm, the tolerable classical launch power can be extended by 5.4 dBm. In the experiment, we obtained positive key rates at the optimal block lengths of 2 and 3, respectively. Our results demonstrate the enormous potential of AD in WDM-QKD applications, providing a way for reducing the impact of noise on practical WDM-QKD systems.

Lithium niobate (LN) microring resonators, characterized by an exceptionally high second-order nonlinear coefficient and superior electro-optic tunability, serve as an outstanding platform for the precise control of integrated quantum frequency combs (QFCs). In this study, we introduce a bipartite entanglement criterion to investigate the pairwise entanglement characteristics of QFCs generated via the spontaneous parametric down-conversion (SPDC) process in lithium niobate microring resonators operating below threshold. Furthermore, we propose a universal framework for analyzing multimode squeezing in quadratic frequency combs, enabling the realization of ultrabroadband and high-degree multimode squeezing. We further reveal the underlying physical mechanism: modulation instability (MI), regulated by temporal walk-off control, not only enables the formation of frequency combs but also induces multimode squeezing in the corresponding resonant modes. This study uncovers the previously unexplored role of on-chip multimode squeezing in quadratic frequency combs while facilitating collective noise suppression across multiple modes, thus holding substantial potential for advancing quantum precision measurement and quantum information processing.

Space-time-varying media with moving interfaces unlock new ways to manipulate electromagnetic waves: however, analytical solutions have been limited mostly to interfaces moving at constant velocity or constant proper acceleration. Here we present exact scattering solutions for an arbitrarily accelerating interface, derived directly in the laboratory frame through a suitable change of variables. We show that acceleration introduces rich effects that do not occur with uniform motion, including transitions between multiple velocity regimes, multiple scattering events, and generalized frequency chirping. We also solve the inverse problem of designing an interface trajectory that produces a desired chirping profile, demonstrating how tailored acceleration can synthesize complex frequency modulations. These results provide a fundamental framework to understand and control wave interactions with accelerated boundaries, opening pathways for advanced applications in space-time signal processing and dynamic pulse shaping.

We show that the Purcell effect can lead to a substantial enhancement in the maximum cooling power for solid-state laser cooling. We numerically demonstrate such enhancement in a patterned slot-waveguide structure using ytterbium-doped silica as the active material. The enhancement arises primarily from the increase of saturation power density and the escape efficiency, and can persist in spite of the presence of parasitic absorption in the structure surrounding the active material. Our results point to an opportunity in photonic structure design for optical refrigeration.

Optical fiber bundles enable diffraction-free transmission of two-dimensional optical field distributions between the bundle input and output ends, which is highly beneficial in many applications in remote sensing and imaging. The spatial resolution of fiber bundles is mostly limited by the mode field diameter of an individual fiber. When using common low-refractive-index fibers, the resolution is typically limited by the wavelength of light ($\sim \lambda$), while using high-refractive-index fibers allows pushing it into a subwavelength range ($\simeq 0.3\lambda$–$0.5\lambda$), as was recently reported for sapphire fiber bundles in the terahertz (THz) range. Despite advanced resolution, such bundles require complicated image readout aided by depixelization techniques based on computational imaging. The analytical models of image formation in such systems are largely absent, which hampers the development of such bundles, as well as efficient processing of collected images. In this paper, we develop a semi-analytical model based on the methods of Fourier optics and sampling theorem to answer the fundamental questions related to image quality and resolution of such bundle-based imaging systems within the modulation transfer function (MTF) formalism. Thus, the developed model is then applied to analyze the THz image formation by the tapered sapphire fiber bundles. The inferred MTFs agree with the experiments. We believe that our findings should be instrumental for designing and applications of optical fiber bundles.

Random number generators are an integral part of any cryptographic system. The security of the cryptographic system depends on the quality of the random number generators. In this work, we demonstrate a high-entropy (more than $0.95$ bits/bit) photon number source using a femtosecond pulsed laser that uses chirped-pulse amplification as a mechanism. The randomness arising from inherent thermal fluctuations is comprehensively analyzed. We further propose and analyze a randomness conditioning algorithm, the Borel Selector, which in real time produces an output that is an ($ϵ,m$)-limiting Borel sequence. The physical entropy source, as well as the conditioning algorithm, has been benchmarked against state-of-the-art methods, and demonstrated improved statistics and increased efficiencies. The proposed entropy source and extractor is, to our knowledge, the first of its kind, and is a promising candidate for application in entropy-as-a-service and postquantum cryptography architectures.