Optics express最新文献

Reducing the power consumption of on-chip systems is of critical importance for large-scale photonic integration. Thermo-optic phase shifters, with advantages such as broadband response, CMOS compatibility, and fabrication simplicity, remain widely used in integrated photonics, yet their relatively high power consumption continues to be a major limitation for large-scale applications. Here, we introduce and experimentally demonstrate a mode-cycling topology that enhances thermo-optic modulation efficiency by sequentially converting the optical field among different guided modes, which forces the light to traverse the phase-shifting region multiple times under the same heater. This cycling in the mode domain effectively multiplies the light-matter interaction without enlarging the device footprint. The scheme employs an inverse-designed bi-directional (de)multiplexer and a mode exchanger, which provide compactness, low loss, and improved robustness compared to conventional asymmetric directional couplers. As a proof of concept, we fabricated a 2 × 2 mode-cycling thermo-optic enhanced switch. The measured results show the average insertion losses at about 2.5 dB with a dynamic extinction ratio over 32.7 dB. The device exhibits a half-wave power of approximately 11.9 mW, nearly halving the power requirement compared to a conventional reference switch of similar size. These results confirm the validity of the mode-cycling topology and highlight its potential as a scalable route toward energy-efficient and compact photonic integrated systems.

Amorphous glass scintillators are designed, and the radio-luminescence and density are modulated by GdF₃ concentration. The glass density is enhanced to 4.62 g/cm³, which is higher than oxyfluoride glass ceramics, and increases the absorption coefficient for X-rays. The radio-luminescence intensity of optimum glass is higher than that of traditional glass scintillators and even 22 times higher than commercial Bi₄Ge₃O₁₂ (BGO) crystal. Clear imaging photos of objects such as an earphone, metal springs, a peanut, and an integrated circuit chip are all obtained by using the designed glass as a scintillator with a spatial resolution of 20.4 lp/mm. This work provides a strategy for engineering an excellent glass scintillator for clear X-ray imaging.

Accurate terahertz scattering models for multilayer building materials are vital for the design of 6G systems, but current methods are either too simple or computationally expensive. We introduce a hybrid multilayer scattering model that unites a recursive method for coherent scattering with the scalar Kirchhoff approximation for the incoherent portion; a physics-based coefficient partitions power between these components. Compared with the experimental data, the proposed model can decrease the root-mean-square error by as much as 89.6 % when modeling complex laminated materials. The proposed model is a physically robust and computationally efficient tool for designing THz imaging tools and indoor 6G networks.

Fiber bundle imaging systems suffer from sampling artifacts such as honeycomb patterns due to their discrete and non-uniform fiber layout, fundamentally limiting image resolution. Conventional reconstruction methods rely on precise calibration of the fiber layout or learning from paired datasets, both of which have limited generalization across imaging setups and require sample-specific preparation. We present an unsupervised method for reconstructing high-resolution images using a burst of misaligned frames that does not require known fiber layout, paired training data, or per-sample calibration. Our approach jointly solves motion estimation and image reconstruction through test-time training. We model each burst frame as a deformed observation of a single canonical view, parameterizing the underlying motion with a coordinate-based network. A second coordinate-based network learns a joint super-resolved scene representation shared across aligned frames. Both networks are trained jointly end-to-end without paired ground truth or external supervision. Simulation and experimental results demonstrate that our method robustly removes fiber bundle artifacts and generalizes to various sample types. We also released a benchmark dataset for optical fiber bundle imaging to facilitate future research.

This article proposes a polarization-insensitive speckle spectrometer based on a cascaded structure of short multimode fiber (MMF) and ground glass diffuser (GGD), and conducts experimental verification. Compared with traditional spectrometers based on long MMF, the use of cascaded scattering media composed of short MMF and GGD significantly shortens the physical length of key scattering elements, thereby helping to achieve more compact core components. The random scattering introduced by GGD enhances the diversity and specificity of speckle patterns. This can significantly improve the spectrum encoding capability and the system's robustness to interference. In addition, a spectral reconstruction method based on a multidimensional polarization database has been introduced. This method is based on a multidimensional polarization database and can perform high-precision spectral reconstruction on incident light of any polarization, effectively compensating for changes caused by polarization. This system demonstrates the ability to simultaneously reconstruct multiple unknown polarization state spectra from composite inputs, validating the system's ability to address the problem of signal-to-noise ratio (SNR) deterioration caused by polarization blind point (PBP). This study provides an effective technical approach to address the challenges of stability, resolution, and polarization dependence in speckle spectrometers, and lays the foundation for developing the next generation of compact, stable, and polarization insensitive speckle spectrometers.

Mode-locked lasers operating in the 2 μm region are of great value for various spectroscopic applications and investigations of laser-matter interactions. However, ultrafast lasers that exhibit both a short pulse duration and a wide emission spectrum below 1.9 μm remain challenging. In this work, a passively mode-locked Tm:CaF₂ laser was demonstrated at approximately 1886.2 nm with a pulse duration of 3.7 ps and a maximum average output power of 171 mW, by using Gires-Tournois interferometer mirrors for intracavity dispersion compensation. In contrast, the introduction of Gd³⁺ co-doping enabled the first realization of a mode-locked Tm,Gd:CaF₂ laser, which generated significantly shorter pulses of 1.7 ps. Moreover, the Tm,Gd:CaF₂ laser exhibited a broadened tuning range of 142.2 nm compared to 127.6 nm obtained in the Tm:CaF₂ laser. These results confirm that co-doping Gd³⁺ ions enhances the performance of Tm-based CaF₂ lasers, making Tm,Gd:CaF₂ crystals a promising gain medium for a broadband mode-locked laser around 1.9 μm.

Polarimetry plays a pivotal role in diverse fields ranging from astronomy to biomedical imaging. However, the widespread adoption of full-Stokes polarimeters is constrained by the bulkiness of traditional optical components (e.g., wave plates) and the fabrication complexity of emerging metasurfaces, which typically require costly lithography and rigorous pixel-to-structure alignment. Here, we demonstrate a cost-effective, single-shot full-Stokes polarimeter based on a disordered twisted nanohole array (DTNA) metasurface, fabricated via scalable microsphere lithography. By leveraging the intrinsic long-range disorder and moiré-induced anisotropy, the device generates spatially diverse optical responses that robustly encode arbitrary polarization states. To decode this information without complex physical calibration, we develop a deep learning framework that establishes an end-to-end mapping between the spatially encoded intensity distribution and the full Stokes vector. The system achieves high-precision reconstruction with normalized mean squared errors (MSEs) of 0.047%, 0.16%, and 0.032% for S₁, S₂, and S₃, respectively. Furthermore, through a systematic investigation of training data distribution, dataset volume, and super-pixel size, we identify the physical origin of this performance: the synergistic interaction of microscopic optical disorder (initial-phase, linear dichroism (LD), and circular dichroism (CD)) creates a high-dimensional feature space, where detection accuracy improves with increased disorder until reaching an information saturation point. This work not only offers a robust, alignment-free paradigm for high-performance integrated polarimetry but also provides fundamental insights into the role of disorder in computational optical sensing.

Three-dimensional (3D) microscopic imaging techniques are facing challenges to achieve greater imaging depth and enhanced visualization of results. In this paper, we propose a 3D microscope acquisition method based on a liquid lens with the translational field of view (LLTFOV). The method utilises the fast zoom function of the LLTFOV to achieve rapid depth focusing of the microscope, obtain parallax images of the specimen with complete depth information, and improve the accuracy and reliability of 3D reconstruction. By utilizing the LLTFOV's precise field of view (FOV) adjustment function, the parallax image of the specimen with multi-angle, uniform, and no vertical parallax is obtained, and the vizualisation effect of the 3D image of the specimen is improved. The 3D image of the specimen is obtained by displaying the acquired parallax synthesis image using a 3D display screen. The experimental results demonstrate that the method can efficiently reproduce the 3D images of the specimens, improving the image quality and visual experience, making it easier to obtain high-quality 3D images in scientific research and applications.

We present an ultra-efficient microheater on a sub-micron-thick InP membrane, designed with direct waveguide heating by an epitaxially grown, vertical dual-layer structure. With minimized heat capacity and thermal leakage, this design achieves a phase tuning efficiency of 1.11 mW/π, switching time of around 10 µs, and a tuning range of more than 3π within a functional length of 19 µm. We then demonstrate one order of magnitude further speed enhancement by an improved pulse-driving method, which minimizes the output optical signal distortion, pushing the switching down to 870 ns.

We report the demonstration of single-frame randomized probe imaging (RPI) using a 13.5 nm extreme ultraviolet (EUV) beam from a table-top high-harmonic generation (HHG) source. Three types of beams-a smooth, vortex, and speckle beam-were used to investigate the effect of different illuminations on image quality. Single-frame RPI reconstructions were successfully achieved for all beam types, with the highest resolution of 110 nm obtained using the EUV speckle beam. Comparisons with ptychography reconstructions confirm the advantages of structured illuminations over a smooth beam, showing improved convergence and image fidelity. Furthermore, averaging a small number of RPI images reconstructed from individual diffraction patterns significantly improves the resolution to sub-100 nm. These results demonstrate the capability of single-frame RPI to deliver rapid, high-resolution EUV imaging, offering a promising approach for applications limited by acquisition time, such as ultrafast pump-probe studies and real-time feedback.