ACS Photonics最新文献

The bulk–boundary correspondence has been widely employed to characterize the band topology of various structures with crystalline symmetries. This concept has been established in both traditional topological phases and higher-order topological phases. Recently, the topological disclination (TD), a type of crystallographic defect derived from two-dimensional (2D) topological crystalline insulators (TCIs), has been demonstrated to support the bulk-disclination correspondence, which goes beyond the material edges. In this study, we extend two relationships to a three-dimensional (3D) photonic model and propose a bulk–boundary-disclination correspondence (BbdC), aiming to enrich the diversity of topological phases across different dimensions based on a single model. By introducing a cutting–gluing process into a stacked TCI architecture, we have fabricated a 3D sample with one-dimensional (1D) TD tunnels. A further tuning of the in-plane and out-of-plane coupling strengths enables more diversified phase transitions, ranging from 2D to zero-dimensional (0D) topological modes, along with distinct TD states. We also discuss another mechanism that supports BbdC by introducing vertical next-nearest-neighbor coupling in the 3D photonic lattice. Our research integrates the topological modes from material surfaces, hinges, edges, and corners to disclination cores and paths and offers a potential vision for exploring multiple-dimensional topological phases in optical devices.

Photonic reservoir computing (PRC) has emerged as a promising framework for ultrafast, low-power information processing. While increasing the number of physical or virtual nodes can improve performance, it also substantially raises hardware and computational complexity. In this work, we propose a simplified PRC architecture that uses only two Mach–Zehnder modulators (MZMs) and photodetectors. By exploiting the intrinsic sinusoidal response of MZMs, our system replaces conventional quadratic functions with sine-squared modulation, enabling up to seventh-order nonlinear transformations at the input layer. Compared to Volterra-based next-generation PRC schemes, our design achieves comparable computational accuracy with significantly reduced structural complexity. Experimental results demonstrate symbol error rates of 5.56 × 10^–4 and a normalized mean square error of 0.155 on the nonlinear channel equalization (NCE) and tenth-order Nonlinear Autoregressive Moving Average (NARMA10) benchmarks, respectively, using only 16 and 22 feature dimensions. These findings underscore the potential of our architecture to simplify physical reservoir computing implementations while boosting computational efficiency and scalability for integrated photonic platforms.

Low-loss and high-efficiency optical phase shifters, as essential components in optical communication, have attracted significant attention in the field of photonic integrated circuits. However, phase shifters based on silicon microring (Si-MRR) often face challenges such as fabrication complexity, high loss, low efficiency, and high power consumption. In this work, we propose a high-efficiency nonvolatile phase shifter by integrating two-dimensional (2D) ferroelectric NbOI₂ into a Si-MRR waveguide. Our results reveal an effective refractive index modulation of −22.95 × 10^–3 RIU (refractive index unit) while preserving nearly constant extinction ratio and resonant line width. Significantly, these devices exhibit an exceptional modulation efficiency of 0.0265 V·cm with low optical loss, which surpasses the performance of earlier research results on 2D material-based phase shifters. Moreover, this work validates the nonvolatile stability of the devices and their advantages in multilevel switching and trimming initial phase errors in the symmetric Mach–Zehnder interferometer (MZI). These advantages make the proposed phase shifter highly promising for applications in the field of silicon photonics, such as optical communication and optical neural networks.

High-directivity beam steering critically overcomes severe path attenuation in terahertz (THz) links by enhancing equivalent isotropic radiated power (EIRP), sensing resolution, and field of view (FoV). Reconfigurable THz beamforming devices still confront challenges in steering coverage and precision, in loss mitigation, and particularly in array scalability requiring element-level tuning. Here, a horn-fed Risley-prism metalens antenna (RP-MLA) is developed to achieve high-gain THz beam steering over ±50° FoV. Two cascaded 3.1 in. aperture metasurfaces, patterned with prism/lens-like phase profiles on high-resistivity silicon wafer, are servo-driven to dynamically reconfigure the phase gradient for steering. An evaluation workflow is proposed to quantify steering efficiency and beam gain in electrically large RP-MLA arrays. The prototype demonstrates a peak gain of 38 dBi and beam-pointing accuracy <0.5°, along with sidelobe suppression >20 dB and a 3 dB gain roll-off at extreme steering angles. Active beam squint correction is realized over a −3 dB bandwidth of 320–370 GHz. The RP-MLA-enabled transceiver uniquely combines THz-aware adaptive beam alignment, concealed object imaging, and focal probing, delivering an integrated communication-sensing solution with a superior performance-to-cost ratio.

Bright two-photon photoluminescence (TPPL) is highly desirable for imaging and optoelectronic applications. The methods to effectively enhance the two-photon emission mainly take advantage of the high local field and large local density of optical states by utilizing excitation resonance and emission resonance in well-designed photonic structures. However, the efficient TPPL process in cavities still remains challenging, since the existing design does not fully take advantage of plasmonic resonances for either excitation or emission enhancement. In this work, we demonstrate a straightforward strategy to enhance the TPPL from CdSe/ZnS quantum dots (QDs) in a convenient double-resonance plasmonic cavity, consisting of a gold nanoparticle on a film with a monolayer QDs spacer. By simultaneously aligning excitation and emission with the plasmonic modes, TPPL enhancement of 7 orders of magnitude is achieved, including 48.0-fold emission enhancement. Moreover, simulations show that the local density of optical states at the emission resonance can be as high as 9 × 10³. Our work showcases the potential of nanophotonic systems for nonlinear optical phenomena at the nanoscale.

Fabrication of diffractive optical elements (DOEs) is typically slow, costly, and requires specialized expertise, motivating the need for a rapid and accessible alternative. Here, a maskless, cost-effective grayscale lithography approach is introduced for the rapid fabrication of DOEs. The method relies on the single-step projection of a grayscale pattern onto a droplet of UV-curable resin, followed by immersion-oil sealing under near-index-matching conditions. This process reduces the fabrication cycle from several days to about 10 min, remains user-friendly and reliable, and does not require specialized skills. A calibration procedure enables conversion of a phase map into a grayscale pattern without requiring precise direct measurements of the refractive index. The approach demonstrates the fabrication of a vortex plate, Zernike polynomial masks, and phase masks for 3D localization microscopy, all showing strong agreement with simulations. The technique does not require specialized facilities and can be implemented with desktop resin 3D printers, making custom DOE prototyping accessible to a wide range of researchers.

Thin-film lithium niobate is a promising integrated nonlinear photonics platform due to its strong second- and third-order nonlinear response. However, these off-resonant nonlinear mechanisms typically require high input optical powers beyond the microwatt level. In this work, we achieve optical nonlinearity at picowatt input power by incorporating the strong resonant nonlinear absorption of rare-earth ions into high-quality-factor thin-film lithium niobate ring resonators. By precisely controlling the output coupling strength of the resonator, we demonstrate multiple nonlinear response behaviors including optical limiting and negative differential transmission, in which the output power decreases with increasing input power. These nonlinear responses are well described by a model of an ensemble of inhomogeneously broadened three-level atoms coupled to a cavity. We also demonstrate optical bistability and hysteresis of the device with a bistable lifetime of approximately 3 ms. This versatile low-power nonlinear device can serve as a fundamental building block for nonlinear thin-film lithium niobate photonic circuits.