Vectorial states of light, where the polarization is inhomogeneously distributed in space, have gained considerable interest in the context of structured light, but their inherent parity has hitherto been overlooked. Now, parity has been revealed as a fundamental degree of freedom in vectorial light that can be acted on with customized metasurfaces, opening a path to high capacity classical and quantum communication.

The article comments on a recent advance in large-scale distributed diffractive-interference hybrid photonic chiplet Taichi for artificial general intelligence applications.

Prof. Jelena Vučković (Stanford University) discusses her research and inspirations, in conversation with Advanced Photonics Early Career Editorial Board Member Prof. Menjie Yu (University of Southern California).

Super-Bloch oscillations (SBOs) are amplified versions of direct current (dc)-driving Bloch oscillations realized under the detuned dc- and alternating current (ac)-driving electric fields. A unique feature of SBOs is the coherent oscillation inhibition via the ac-driving renormalization effect, which is dubbed as the collapse of SBOs. However, previous experimental studies on SBOs have only been limited to the weak ac-driving regime, and the collapse of SBOs has not been observed. Here, by harnessing a synthetic temporal lattice in fiber-loop systems, we push the ac-field into a strong-driving regime and observe the collapse of SBOs, which manifests as the oscillation-trajectory localization at specific ac-driving amplitudes and oscillation-direction flip by crossing collapse points. By adopting arbitrary-wave ac-driving fields, we also realize generalized SBOs with engineered collapse conditions. Finally, we exploit the oscillation-direction flip features to design tunable temporal beam routers and splitters. We initiate and demonstrate the collapse of SBOs, which may feature applications in coherent wave localization control for optical communications and signal processing.

The deformation, flicker, and drift of a light field owing to complex media such as a turbulent atmosphere have limited its practical applications. Thus, research on invariants in randomly fluctuated light fields has garnered considerable attention in recent years. Coherence is a statistical property of light, while its full and quantitative characterization is challenging. Herein, we successfully realize the orthogonal modal decomposition of partially coherent beams and introduce the application of coherence entropy as a global coherence characteristic of such randomly fluctuated light fields. It is demonstrated that coherence entropy remains consistent during propagation in a unitary system by unraveling complex channels. As representative examples, we study the robustness of coherence entropy for partially coherent beams as they propagate through deformed optical systems and turbulent media. Coherence entropy is anticipated to serve as a key metric for evaluating the propagation of partially coherent beams in complex channels. This study paves the way for a broader application scope of a customized low-coherence light field through nonideal optical systems and complex media.

Advances in laser spectroscopy have enabled many scientific breakthroughs in physics, chemistry, biology, and astronomy. Optical frequency combs pushed measurement limits with ultrahigh-frequency accuracy and fast-measurement speed, while tunable-diode-laser spectroscopy is used in scenarios that require high power and continuous spectral coverage. Despite these advantages of tunable-diode-laser spectroscopy, it is challenging to precisely determine the instantaneous laser frequency because of fluctuations in the scan speed. Here, we demonstrate a simple spectroscopy scheme with a frequency-modulated diode laser that references the laser on-the-fly to a fiber cavity. The fiber cavity’s free spectral range is on-the-fly calibrated with sub-10-Hz frequency precision. We achieve a relative precision of the laser frequency of 2×10−8 for an 11-THz frequency range at a measurement speed of 1 THz/s. This is an improvement of more than 2 orders of magnitude compared to existing diode-laser-spectroscopy methods. Our scheme provides precise frequency calibration markers, while simultaneously tracking the instantaneous scan speed of the laser. We demonstrate the versatility of our method through various applications, including dispersion measurement of a fiber, ultrahigh-Q microresonators, and spectroscopy of a hydrogen fluoride gas cell. The simplicity, robustness, and low cost of this spectroscopy scheme are valuable for out-of-the-lab applications like lidar and environmental monitoring.

Three-dimensional (3D) imaging with structured light is crucial in diverse scenarios, ranging from intelligent manufacturing and medicine to entertainment. However, current structured light methods rely on projector–camera synchronization, limiting the use of affordable imaging devices and their consumer applications. In this work, we introduce an asynchronous structured light imaging approach based on generative deep neural networks to relax the synchronization constraint, accomplishing the challenges of fringe pattern aliasing, without relying on any a priori constraint of the projection system. To overcome this need, we propose a generative deep neural network with U-Net-like encoder–decoder architecture to learn the underlying fringe features directly by exploring the intrinsic prior principles in the fringe pattern aliasing. We train within an adversarial learning framework and supervise the network training via a statistics-informed loss function. We demonstrate that by evaluating the performance on fields of intensity, phase, and 3D reconstruction. It is shown that the trained network can separate aliased fringe patterns for producing comparable results with the synchronous one: the absolute error is no greater than 8 μm, and the standard deviation does not exceed 3 μm. Evaluation results on multiple objects and pattern types show it could be generalized for any asynchronous structured light scene.

Hyperbolic polaritons are known to exist in materials with extreme anisotropy, exhibiting exotic optical properties that enable a plethora of unusual phenomena in the fields of polaritonics and photonics. However, achieving simultaneous low-dimensionality, high-speed controllability, and on-demand reconfigurability of the polaritons remains unexplored despite their excellent potential in light–matter interactions, photonic integrated circuits, and optoelectronic devices. Here, we propose a metasurface approach to integrating artificially engineered electromagnetic anisotropy with fast-controllable electronic elements, offering a new route to realize active topological polaritons. Experiments showcase the proposed reconfigurable metasurface can support real-time transitions of designer polaritons from elliptical to flat, and then to hyperbolic and circular isofrequency contours. Correspondingly, the in-plane surface wavefront undergoes the transitions from convex to collimating, concave, and eventually back to convex. By exploiting the topological variations in polariton dispersions, we observe intriguing phenomena of controllable field canalization and tunable planar focusing. Furthermore, we report the concept of a planar reconfigurable integrated polariton circuit by spatially tailoring the distributions of polariton isofrequency contours, unveiling rich dispersion engineering possibilities and active control capabilities. We may provide an inspiring platform for developing planar active plasmonic devices with potential applications in subdiffraction-resolution imaging, sensing, and information processing.

Passive radiative cooling is a promising passive cooling technology that emits heat to deep space without energy consumption. Nevertheless, the persistent challenge of overcooling in static radiative techniques has raised concerns. Although a desirable solution is suggested based on vanadium dioxide (VO2) in the form of a Fabry–Perot (F–P) resonant cavity, the inherent contradiction between desired high emissivity (ε) and low solar absorptance (αsol) remains a notable limitation. Here, we employed a simple mask-filling technique to develop a temperature-adaptive metasurface radiative cooling device (ATMRD) for dynamic thermal regulation. Simulation and experimental results substantially evidenced that multiple localized polariton resonances were induced by the VO2 metasurface, significantly enhancing the thermal emittance of the ATMRDs. The engineered ATMRD achieved an amazing switch of the atmospheric window emittance from 0.13 to 0.85 when the surface temperature exceeds a pre-set transition temperature, accompanied by a commendable αsol of 27.71%. The mechanism of multiple localized polariton resonances is discussed in detail to understand the enhanced performance based on the investigation of the relationship between the metasurface structure and multiple localized polariton resonances. We demonstrate an efficient smart radiative technique achieved by a simple micro/nanoprocess and, most importantly, contribute a valuable reference for the design of radiative devices, which is crucial in various areas such as passive cooling, smart windows, multifunctional electromagnetic response, and space application technologies.

The erratum notes the addition of a reference citation that was inadvertently omitted in the originally published article.

The erratum clarifies that the scattering matrix provided in Eq. 29 is valid only for a nonreciprocal system. It also corrects the matrix in Eq. 32(b) in the Appendix of the article.

The article provides information about the image on the cover of Advanced Photonics, Volume 6 Issue 4.