Nature Photonics最新文献

Broad-area semiconductor lasers are used in many high-power applications; however, their spatio-temporal dynamics are complex and intrinsically unstable due to the interaction between transverse lasing modes. Here a dynamical and ultrahigh-resolution spatio-spectral analysis of commercial broad-area lasers reveals multiplets of phase-locked first- and second-order transverse modes that are spontaneously created by the nonlinear dynamics of the laser. Phase locking between modes of different transverse order is confirmed by comparing the linewidths of the lasing modes with that of their beat note and by a direct measurement of their phase fluctuation correlations. The spontaneous phase locking is unexpected since the overall dynamics are unstable and the system lacks any intentional feature to induce locking. This partially synchronized dynamical state with groups of coexisting synchronized and unsynchronized laser modes is similar to chimera states found in networks of coupled oscillators, indicating that such states may exist in a wider range of systems than previously assumed.

Optical atomic clocks have demonstrated revolutionary advances in precision timekeeping, but their applicability to the real world is critically dependent on whether such clocks can operate outside the laboratory. Photonic integration offers one compelling solution to address the miniaturization and ruggedization needed to enable clock portability, but brings with it a new set of challenges in recreating the functionality of an optical clock using chip-scale building blocks. The clock laser used for atom interrogation is one particular point of uncertainty, as the performance of the meticulously engineered bulk-cavity-stabilized lasers would be exceptionally difficult to transfer to chip. Here we demonstrate that an integrated ultrahigh-quality-factor spiral cavity, when interfaced with a 1,348 nm seed laser, is able to reach a fractional frequency instability of 7.5 × 10⁻¹⁴ on chip. On frequency doubling the light to 674 nm, we use this laser to interrogate the narrow-linewidth transition of ⁸⁸Sr⁺ and showcase the operation of a Sr-ion clock with short-term instability averaging down as (3.9times 1{0}^{-14}/sqrt{tau }) (τ, averaging time). Our demonstration of a high-performance optical atomic clock interrogated by an integrated spiral cavity laser opens the door for future advanced clock systems to be entirely constructed using lightweight, portable and mass-manufacturable integrated optics and electronics.

Integrated photonic chips hold substantial potential in optical communications, computing, light detection and ranging, sensing, and imaging, offering exceptional data throughput and low power consumption. A key objective is to build a monolithic on-chip photonic system that integrates light sources, processors and photodetectors on a single chip. However, this remains challenging due to limitations in materials engineering, chip integration techniques and design methods. Perovskites offer simple fabrication, tolerance to lattice mismatch, flexible bandgap tunability and low cost, making them promising for hetero-integration with silicon photonics. Here we propose and experimentally realize a near-infrared monolithic on-chip photonic system based on a perovskite/silicon nitride photonic platform, developing nano-hetero-integration technology to integrate efficient light-emitting diodes, high-performance processors and sensitive photodetectors. Photonic neural networks are implemented to perform photonic simulations and computer vision tasks. Our network efficiently predicts the topological invariant in a two-dimensional disordered Su–Schrieffer–Heeger model and simulates nonlinear topological models with an average fidelity of 87%. In addition, we achieve a test accuracy of over 85% in edge detection and 56% on the CIFAR-10 dataset using a scaled-up architecture. This work addresses the challenge of integrating diverse nanophotonic components on a chip, offering a promising solution for chip-integrated multifunctional photonic information processing.

Leveraging the entire space of complex dielectric permittivity, non-Hermitian photonics has fundamentally altered wave propagation with complex optical potentials and has ushered in a host of new photonic applications. Through parity–time symmetry and its breaking—a delicate interplay between gain and loss—even the interaction between just two entities becomes counter-intuitive and intriguing. Here we realize, through hybrid III–V/Si integration, a scalable non-Hermitian switching network on a two-layer integrated photonic chip. Our platform is a hybrid, with a bottom silicon layer and a top InGaAsP layer that provides optical gain. By tuning the gain level in the top layer, vertically coupled waveguides operate below or above the exceptional point, where light is switched across two layers, among different input–output ports. For a single switching unit, the switching dynamics are ultrafast, on the order of 100 ps. In a large switching network, non-blocking and other diverse connectivities are established in single-wavelength and wavelength-selective switching, with high extinction ratios. Our approach adds scalable non-Hermitian switching to photonic design toolkits to simultaneously boost the switching time and bandwidth density to cutting-edge levels, therefore paving the way for compact and ultrafast monolithic integrated silicon photonics in next-generation optical information networks.

Applications of waves in communications, information processing and sensing need a clear understanding of how many strongly coupled channels or degrees of freedom exist in and out of volumes of space and how the coupling falls off for larger numbers. Numerical results are possible, and some heuristics exist, but there has been no simple physical picture and explanation for arbitrary volumes. By considering waves from a bounding spherical volume, we show a clear onset of a tunnelling escape of waves that both defines a limiting number of well-coupled channels for any volume and explains the subsequent rapid fall-off of coupling strengths. The approach works over all size scales, from nanophotonics and small radiofrequency antennas up to imaging optics. It gives a unified view from the multipole expansions common for antennas and small objects to the limiting plane and evanescent waves of large optics, showing that all such waves can escape to propagation to some degree, by tunnelling if necessary, and gives a precise diffraction limit.