Optics letters最新文献

On-chip photonic systems are essential for next-generation information processing, where multi-way beam splitting can significantly enhance parallelism and processing capacity. Conventional splitters suffer from polarization and wavelength dependence, limited integration density, and poor uniformity. Here, we develop a femtosecond-laser-based quasi-parallel scanning technique to fabricate 3D multi-way splitters with high uniformity (up to 92.62%) and broad bandwidth (750-1050 nm). This approach offers a promising solution for future optical computing, sensing, on-chip communication, and quantum photonic systems.

Understanding the three-dimensional organization of brain microstructure is essential for revealing the functional relationships between neurons and glial cells. We have constructed a Fourier Light Field Fluorescence Polarization Microscopy (FLF-FPM) system that can reconstruct the volumetric distribution of six Stokes-derived polarization parameters, enabling scan-less three-dimensional tomographic imaging of fluorescence intensity and polarization. Applied to ex-vivo mouse brain samples stained with GFP, NeuN, and Iba1, the system reveals distinct depth-dependent polarization signatures for each fluorophore label, reflecting both their intrinsic emission characteristics and tissue scattering effects. FLF-FPM provides a compact, low-cost, and quantitative approach for characterizing cellular morphology, layer-specific organization, and local optical anisotropy in thick brain tissue, offering a new, to the best of our knowledge, platform for investigating the structural basis of neural function.

A femtosecond optical parametric oscillator (fs-OPO) based on type-I (o→e + e) noncollinear phase matching in the yz plane of bismuth triborate (BIBO) crystal is demonstrated, which breaks the bandwidth (700-1900 nm) limit set by collinear phase matching. The pumping source is provided by the second-harmonic (SH, 520 nm) wave of a homemade 1040-nm Yb:fiber femtosecond laser with a pulse duration of 177 fs and a repetition rate of 100 MHz. Experimentally, the wavelengths can be tuned from 626 nm to 3051 nm (626-1026 nm for signal and 1067-3051 nm for idler) by adjusting the angle of the BIBO crystal, which, to the best of our knowledge, is the widest wavelength tuning range for any BIBO-based femtosecond OPO. At the wavelength of 713 nm, the highest average power of 1.3 W is obtained, with a conversion efficiency of 37.1%. If both signal and idler powers are counted in, the total efficiency is 52%, which is a new benchmark. In addition, the compressed pulse duration is measured to be 108 fs at 788 nm, with a time-bandwidth product (TBP) of 0.46. The beam quality factors M² of 788 nm laser are measured to be Mx2=1.38 and My2=1.18, respectively.

Polarization converters for the generation of structured light beams, in particular, optical vortices, are widely used in various fields of science and applications. The search for affordable and adaptable (reconfigurable) systems that allow efficient conversion remains relevant. This paper discusses the formation of a polarization converter through optical modification of a thin layer of an amorphous azobenzene-containing polymer by exposure to a laser beam. Such a material exhibits optical anisotropy due to the redistribution of absorbing fragments caused by light-induced trans-cis transitions. It is shown that under the action of a light beam with an axially symmetric polarization distribution, a corresponding distribution of the induced optical axis is created with a high degree of locality. The induced anisotropy persists up to the melting point and can be rewritten by subsequent exposure to light.

Photon-number superposition states are a valuable resource for quantum information processing and can be deterministically generated using advanced quantum-dot (QD) platforms. Here, we propose a twin-field quantum key distribution (TF-QKD) protocol that employs photon-number superposition states of the form 1-t|0⟩+e^iϕt|1⟩. Numerical simulations show that the protocol outperforms existing laser-based TF-QKD schemes in secret-key rate and transmission distance, surpasses the repeaterless bound, enabling secure communication beyond 210 km under experimentally achievable conditions. A key advantage is its direct compatibility with existing QD technology. As integrated, solid-state, on-demand single-photon sources, QDs inherently provide high stability, scalability, and photon indistinguishability, making them well suited for deployment in large-scale quantum networks. Overall, our work demonstrates a practical pathway toward high-performance long-distance TF-QKD and highlights the broader potential of solid-state non-classical light sources for quantum networking architectures.

Zou-Wang-Mandel (ZWM) quantum-induced coherence has been demonstrated for high-sensitive detection and sensing applications such as high signal-to-noise ratio ranging and imaging in complex environments. The path overlapping of the idler prohibits the determination of the exact path from which the signal originates. However, the interference region of quantum-induced coherence is limited to coherence length of parametric down-conversion (PDC) photons generated by nonlinear processes, which has remained an urgent issue to address. Here, we propose a method to increase the interference region of quantum-induced coherence imaging systems, from micrometers to centimeters at least by seed injection (SI) of the same frequency as the idler, and resulting in brighter fringes. Compared to typical ZWM quantum-induced coherence imaging, our system not only retains the advantages of noise resistance and no coincidence requirement but also exhibits possibilities of high-coherence, long-distance, and high-visibility imaging.

We demonstrate a patterned vertically aligned (PVA) liquid crystal display (LCD) driven by a reverse-voltage scheme that achieves submillisecond response times (0.52 ms). Both simulations and experiments confirm that the device consistently operates within the submillisecond regime, thereby validating the feasibility of the proposed approach. This method optimizes the LC molecular deformation dynamics and reverse-bias driving strategy, effectively overcoming the intrinsic response-time limitations of conventional in-plane switching (IPS) and fringe-field switching (FFS) LCDs, consequently meeting the core requirements of next-generation augmented reality (AR) and virtual reality (VR) display technologies for improved dynamic display performance.

Silica nanocomposites-based processes provided a new route for low-temperature fabrication of fused silica components. However, low accuracy and poor surface quality prohibit their applications for generating fused silica optics. Herein, we report what we believe to be a novel process for ultra-precision fabrication of complex-shaped fused silica micro-optics by diamond turning of partially debound silica nanocomposites, where the partially debound nanocomposites were designed to suppress undesired deformations in the high-temperature processing. By practically characterizing the generated fused silica components, the optimum partial debinding temperature was selected as 275°C. As a demonstration, an achromatic refractive-diffractive hybrid lens with long focal depth was fabricated to have a surface roughness of Sa = 6.01 nm and a PV error of around 0.46 μm.

Photonic switching technologies have been proffered as competitive replacements for electronic switches, due to high power efficiency, high bandwidth density, and low cost. Here, a high-performance 1 × 8 thermo-optic switch based on artificial gauge field engineered waveguide superlattices is proposed. This switch exhibits an average insertion loss of 1.96 dB and keeps crosstalk below -20 dB over a 60 nm bandwidth. By leveraging topology optimization, this thermo-optic phase shifter eliminates the need for intricate air-trench or undercut processes while delivering exceptional metrics: low power consumption (2.52 mW/π), low loss (0.4 dB), sub-1V driving voltage for 2π tuning, wideband operation (60 nm), and a compact footprint (245 μm × 15 μm).

Reliable bonding of non-optical-contact ceramic and glass is crucial for the fabrication of microdevices but remains challenging due to their distinct thermophysical properties and non-uniform interface. In this study, femtosecond laser welding of alumina ceramics with a surface roughness of 4.82 μm and fused silica under non-optical-contact conditions were achieved with a weld strength of 13.75 MPa. The laser parameters (200 fs, 1030 nm, 1000 kHz, 23.8 μJ, 40 mm/s scanning speed) were used for welding. Under the rapid thermal accumulation induced by the high-repetition rate femtosecond laser, the high-speed imaging system captured the coexistence of internal and interfacial plasma, occurring during the welding process. The internal plasma generated by nonlinear absorption remained localized at an almost constant height above the interface during the steady melting stage, while interfacial plasma showed continuous upward growth in sequence and finally produced a discrete modified region both within fused silica and at the interface, indicating it as a highly stable welding process. Detailed analysis revealed that the dual-plasma interaction promotes localized melting, interfacial diffusion, and mechanical interlocking between fused silica and ceramics. This work elucidates the feasibility and dynamic mechanism of femtosecond laser welding of alumina ceramics and fused silica under non-optical-contact conditions, providing experimental and theoretical guidance for precision joining of dissimilar materials.