Optics express最新文献

In this paper, what we believe to be a new highlight removal method based on disparity layering and multi-strategy hierarchical restoration is proposed to address the challenge of large-area specular highlights by using a light field camera array. Initially, the dichromatic reflection model is combined with unsupervised k-means clustering to precisely detect highlight regions and generate multi-view highlight masks. Subsequently, a strategy based on disparity estimation and energy minimization, which guided by the disparity reliability of non-highlight regions, is proposed to properly assign highlight pixels to their corresponding disparity layers. Finally, a multi-strategy hierarchical restoration framework based on multi-view observation availability is designed to adaptively recover highlight pixels within their assigned disparity layers. Furthermore, a composite evaluation metric, named PSSE, is designed to quantitatively assess the overall restoration performance. Experimental results on both public light field datasets and real captured scenes demonstrate that the method effectively removes large-area highlights while preserving geometric structure and photometric consistency, and it shows strong robustness and adaptability in complex textured environments. Compared with single-view methods that often lose structural details and multi-view methods that rely on sequential capture and unstable feature matching, the proposed approach achieves more accurate detection and robust restoration, and it also holds promising potential for industrial inspection and digital preservation of cultural heritage.

Accurately measuring the detection efficiency of confocal microscopes is crucial for assessing performance, yet it remains challenging. Here, we present a rapid, quantitative method that leverages the photoluminescence of a single quantum dot. By analyzing the cross-correlation of photon arrival times from single exciton and biexciton states, we can precisely determine the detection efficiency. This approach takes less than 30 seconds, is highly tolerant of laser power variations, and does not require calibration procedures. This standard provides a convenient benchmark for routine optimization and reliable cross-laboratory comparisons, establishing a crucial foundation for quantitative fluorescence imaging and the advancement of super-resolution microscopy.

We propose and experimentally demonstrate a cost-efficient and scalable LiDAR architecture that enables hybrid solid-state parallel ranging using a single emitter and receiver. The system integrates code-division multiple access (CDMA) temporal modulation with Hadamard matrix-based spatial encoding, forming a dual-modulation framework referred to as SEARCH LiDAR (single-emitter-and-receiver CDMA-Hadamard LiDAR). To address the limitations of conventional mechanical scanning and costly parallel systems, we first implement a hybrid solid-state scanning method via wavelength tuning and CDMA encoding. Building upon this, we realize parallel ranging by introducing a secondary spatial modulation layer using an S-matrix (a type of binary Hadamard matrix). Experimental results confirm the feasibility of the 1D SEARCH LiDAR concept and further suggest a future extension toward fully solid-state 2D scanning using optical switch-array devices. 3D imaging under varying noise conditions demonstrates the superior robustness of the proposed system, particularly in low SNR, due to the combined benefits of CDMA and Hadamard encoding. This work provides a practical path toward low-cost, high-performance LiDAR suitable for next-generation autonomous perception systems.

This paper proposes a low-complexity compressive sensing multiple access (CSMA) communication system based on non-orthogonal sparse codebooks in sparse code multiple access (SCMA) for the special environments of satellite Internet of Things (IoT) communications. At the transmitter (Tx), a measurement matrix constructed from multi-user codebooks measures multi-user data, replacing linear traditional SCMA encoding. At the receiver (Rx), leveraging the sparse characteristic of active satellite IoT users, the smoothed L0 (SL0) algorithm is used instead of the traditional message passing algorithm (MPA) and logarithmic-message passing algorithm (Log-MPA), significantly reducing the number of multiplication operations and, in turn, greatly lowering computational complexity. The proposed scheme has been experimentally validated in a W-band wireless communication system with a transmission distance of 6 meters and 12 meters, achieving 4.5 Gb/s. For input optical power (IOP) ranging from -3 dBm to 3 dBm, whether in the case of 1/6 or 1/3 user activity, the bit error rate (BER) performance of the SL0 algorithm outperforms that of the MPA and Log-MPA. Furthermore, in terms of computational cost, the SL0 algorithm can achieve a maximum 85.7% and 72.8% in computational complexity reduction rate (CCRR) compared to the MPA and Log-MPA, respectively. These results indicate that the proposed scheme has significant potential for application in satellite IoT communication scenarios.

Under high-power operation, the transverse mode instability (TMI) effect has become a primary limitation to further power scaling of Yb-doped fiber (YDF) lasers while maintaining high beam quality. Existing mitigation strategies, such as optimizing fiber coiling or pump configurations, fail to address the material-level origin of TMI. In this study, we effectively suppressed TMI by constructing a phosphorus-rich environment of Yb³⁺ and precisely tuning the P/Al doping ratio and fluorine content in YDF. Using an all-fiber MOPA system incorporating our four custom-designed 30/400 μm double-cladded YDFs, the optical-to-optical efficiency was improved from 64.7% to 77.9%, and the TMI threshold increased from 1.9 kW to 3.3 kW. The results further indicate that optimizing the dopant composition plays a significant role in stabilizing the Yb³⁺ valence state and mitigating the TMI effect, underscoring the central role of multicomponent regulation in enhancing fiber performance. This study not only offers a theoretical basis for material optimization of high-power YDF lasers, but also lays the groundwork for their deployment in high-brightness-demanding applications such as aerospace, precision manufacturing and laser therapy.

We present an ultrasensitive fiber-optic curvature sensor based on a micro-air-bubble Fabry-Pérot interferometer (MFPI) that incorporates a micro-optomechanical coupling (MOC) mechanism via two specially designed fiber tapers. During bending, the upstream non-adiabatic taper creates a curvature-dependent refractive index wedge, which steers the guided mode off-axis and shifts its entry point into the spherical MFPI cavity. This mechanism greatly enhances optical-path-difference (OPD) modulation efficiency and wavelength sensitivity. These effects are governed purely by bend-induced radial beam deflection through MOC, rather than by conventional cavity-length change. Despite an overall length of only ∼740 µm, the sensor achieves a remarkable curvature sensitivity (-15.24 nm/m^-1 over 0.42-1.13 m^-1) and intensity sensitivity (-15.31 dB/m^-1 for curvatures <0.42 m^-1), which are one to two orders of magnitude higher than those of conventional single-cavity Fabry-Pérot sensors. Furthermore, the sensor exhibits negligible temperature cross-sensitivity and good repeatability, making it well-suited for high-precision, real-time curvature monitoring in confined or thermally variable environments (e.g., soft-robotic joints or steerable catheters).

Multi-mode photonic molecules (MMPMs) based on cavity-coupled waveguide systems exhibit remarkable potential for diverse applications owing to their enhanced light-matter interactions. However, the fundamental mechanisms underlying mode-mode coupling remain inadequately understood, significantly impeding the development of advanced functional optical devices. To address this issue, we designed a theoretical framework based on the time coupled mode theory (TCMT) to elucidate the mode-mode interaction relationships within multimode optical molecules. To validate the universality of our model, we designed a plasmonic configuration featuring an aperture side-coupled slot cavity and a ring cavity. By introducing symmetrical breaking into the structure, we achieved a substantial enhancement in spectral properties, including a 44-fold improvement in the figure of merit (FOM) and a sensitivity of 1200 nm/RIU. These results pave the way for understanding the underlying physics of optical mode interactions and for achieving high-performance photonic devices.

Entanglement, one of the most representative phenomena in quantum mechanics, has been widely used for fundamental studies and modern quantum technologies. In this paper, we report the observation of nonlocal cancellation and addition of optical rotations with polarization-entangled photons in fructose solutions. The entanglement also enables probing optical activities at a distance by joint measurements on the entangled photons. The good agreement between the experimental results and theoretical predictions demonstrates the potential for extending these measurements to other chiral molecules, with a sensitivity that improves as the number of entangled photons increases.

The design of gain chips for hybrid integration with photonic integrated circuits (PICs) is studied and highlights the benefits of incorporating at least one reflector in the III-V gain material. Quantum dot (QD)-based gain chips with a multi-mode interference (MMI) reflector (MMIR) offer fabrication simplicity and good performance in the O-band. The inclusion of an MMIR in a ridge waveguide (RWG) laser reduces the threshold current by 87% (6 mA vs 46 mA for 1 mm length) and leads to higher slope efficiency, indicating over 90% mirror reflectivity, as compared to Fabry-Perot structures. Both 1- and 2-port designs will simplify alignment of active and passive waveguides for hybrid integration and are strong candidates for large-scale PIC applications.

We investigate theoretically and numerically the use of nonlinear optics to measure the spatial distribution of the gas density in the core of antiresonant hollow-core optical fibres. Short pump and signal laser pulses at different wavelengths and with controlled delay are launched into the fibre. Due to their different group velocity, they overlap within a certain region of the fibre where their nonlinear interaction create an idler pulse (via four-wave mixing) and/or the signal pulse experiences a nonlinear phase shift induced by the pump pulse via cross phase modulation. As the optical nonlinearity in these fibres is dominated by the gas content, a measurement of the idler power or signal phase shift at the fibre output thus provides information about the gas density (its pressure) at the pulse overlap position. We discuss the feasibility of the scheme and its dependence on fibre and pulse parameters. We conclude that such distributed gas measurements are possible within current experimental parameters and can potentially measure pressures far below current experimental techniques with high spatial resolution.