Nature Photonics最新文献

Propelled by advancements in artificial intelligence, the demand for field-programmable devices has grown rapidly in the last decade. Among various state-of-the-art platforms, programmable integrated photonics emerges as a promising candidate, offering a new strategy to drastically enhance computational power for data-intensive tasks. However, intrinsic weak nonlinear responses of dielectric materials have limited traditional photonic programmability to the linear domain, leaving out the most common and complex activation functions used in artificial intelligence. Here we push the capabilities of photonic field-programmability into the nonlinear realm by meticulous spatial control of distributed carrier excitations and their dynamics within an active semiconductor. Leveraging the architecture of photonic nonlinear computing through polynomial building blocks, our field-programmable photonic nonlinear microprocessor demonstrates in situ training of photonic polynomial networks with dynamically reconfigured nonlinear connections. Our results offer a new paradigm to revolutionize photonic reconfigurable computing, enabling the handling of intricate tasks using a polynomial network with unparalleled simplicity and efficiency.

Wideband optical isolators are critical for the robust operation of virtually all photonic systems. However, they have been challenging to realize in the integrated form due to the incompatibility of magnetic media with these circuit technologies. Here we present the first-ever demonstration of an integrated non-magnetic optical isolator with terahertz-level optical bandwidth. The system comprises two acousto-optic beamsplitters that create a non-reciprocal multimode interferometer exhibiting high-contrast, non-reciprocal light transmission. We dramatically enhance the isolation bandwidth of this system by precisely balancing the group delays of the paths of the interferometer. Using this approach, we demonstrate integrated non-magnetic isolators with an optical contrast as high as 24.5 dB, insertion losses as low as −2.16 dB and optical bandwidths as high as 2 THz (16 nm). We also show that the centre frequency and direction of optical isolation are rapidly reconfigurable by tuning the relative phase of the microwave signals used to drive the acousto-optic beamsplitters. With their complementary metal–oxide–semiconductor compatibility, wideband operation, low losses and rapid reconfigurability, such integrated isolators address a key barrier to the integration of a wide range of photonic functionalities on a chip.

Imaging large cleared tissues requires scaling the throughput of imaging techniques. Light sheet microscopy is a promising technique for high-throughput imaging; however, its reliance on conventional microscope objectives limits the optimization of the trade-off between spatial resolution and field of view. Here we introduce curved light sheet microscope to perform optical sectioning with curved light sheets. This concept addresses the long-standing field curvature problem and lowers the barriers in designing high-throughput objectives. Leveraging a customized objective, the curved light sheet microscope achieves diffraction-limited resolution of 1.0 μm laterally and 2.5 μm axially, with uniform contrast over a field of view of more than 1 × 1 cm². Our technique is also compatible with various tissue clearing techniques. We demonstrate that imaging an entire intact cleared mouse brain at a voxel size of 0.625 × 0.625 × 1.25 μm³ can be completed in less than 3 h, without the need for image tiling. We share a full optical description of the objective and report imaging of neuronal and vascular networks, as well as tracing of brain-wide long-distance axonal projections in intact mouse brains.

Time is, figuratively and literally, becoming the new dimension for crystalline matter. In a key recent advance, temporal and spatiotemporal crystals that exhibit periodicity in time and space-time, respectively, were reported, with unique properties such as spectra containing gaps not only in energy but also in momentum. Conversely, the field of topological physics, which has led to celebrated discoveries such as topological insulators featuring protected conducting surface states with immunity to backscattering, has so far been based on the notion of energy gaps and spatial boundaries only. Fundamentally rethinking the role of time, which in contrast to space exhibits a unique unidirectionality called the ‘arrow of time’, thus promises a new dimension for topological physics, setting paradigms of time and space-time topology based on the topological properties of momentum and energy–momentum gaps. Indeed, previous work has shown simulations of states which arise through the topology of momentum gaps and localize at temporal interfaces. Here we enter this new dimension of time and space-time topology. First, using discrete-time quantum walks on synthetic photonic lattices in coupled optical fibre loops, we observe such time topological states. We find a time-topological invariant and establish its relation to the observed time topological states. Transcending the separate concepts of space and time topology, we then propose and implement a system with an energy–momentum gap and introduce the concept of space-time topology, leading to topological states that are localized in both space and time, thus forming space-time topological events. We demonstrate that these are associated with unique effects such as causality-suppressed coupling or the limited collapse of space-time localization. Our study provides a model of time and space-time topology, highlighting an interplay of momentum and energy gap topology with applicability beyond photonics. In the field of topological physics, we anticipate a new role of causality and non-Hermiticity inspired by time and space-time topology. These concepts further invite exploration of connections to other fields where the arrow of time plays an important role. Moreover, our results enable the topological shaping of waves in space and time, with applications in spatiotemporal wave control for imaging or communication and topological lasers, for example.