Topological lasers have emerged as a promising platform for robust photonic systems, yet current implementations relying on semiconductor microcavities and resonators suffer from fundamental constraints including low optical gain, limited output power and fixed lasing sites. To address these challenges, we present an all-solid-state, reconfigurable topological laser based on a Su-Schrieffer-Heeger waveguide array platform, fabricated in disordered laser crystal (Nd:BaLaGa3O7). Harnessing the high gain provided by solid-state lasers, we experimentally and theoretically demonstrate single-mode, continuous-wave topological lasing with output power surpassing 100 mW. In addition to conventional topological edge lasing, we observe topological lasing at trivial lattice terminations and reconfigurable interface sites at arbitrary lattice positions. This unconventional behavior arises from the non-Hermitian parity-time symmetry transition in subsystem at elevated pump power. Our work demonstrates on-demand, site-selectable topological lasing, offering both fundamental insights into topological phase transitions in non-Hermitian systems and practical opportunities to develop robust, reconfigurable topological photonic devices for advanced lasing and optical information processing. Topological lasers usually emit light from a fixed spot. Here, authors report on an all-solid-state platform where topological lasing is demonstrated at trivial lattice terminations as well as at reconfigurable arbitrary sites. The device consists of a Su-Schrieffer-Heeger waveguide array, printed in a disordered Nd:BaLaGa₃O₇ crystal.

An archive system that encodes information in modified optical properties of glass could be a fast, efficient way to store huge quantities of data. An archive system that encodes information in modified optical properties of glass could be a fast, efficient way to store huge quantities of data.

Heterostructured nanointerfaces composed of ordered nanoparticles integrated with non-plasmonic functional materials offer broad application potential but remain limited by the lack of flexible and scalable fabrication techniques. This study presents a two-step top-down approach for constructing plasmonic architectures in neodymium-doped disordered crystals, enabling optical data inscription and encryption. Ion implantation is used to introduce nanoparticle precursors into the subsurface region of the crystal. Then, femtosecond laser-induced nonlinear near-field optical forces drive the redistribution of nanoparticles along the laser propagation path, facilitating the formation of ordered 3D nanoshell structures. By precisely tuning the laser irradiation power, the resonance modes of the hybrid system are modulated, allowing for controlled upconversion luminescence in rare-earth-ion-based plasmonic structures. The proposed method supports multifunctional optical applications, including data storage, encryption, and fluorescence/photoluminescence readout. This work establishes a general strategy for tailoring plasmon-enhanced optical responses in rare-earth-doped crystalline materials and can be used for opto-electronic and passive/active optical control.

We report on the fabrication and mode modulation of telecom-band depressed-cladding waveguides in SK1310 glass. To obtain high-quality depressed-cladding waveguides, the effects of two primary femtosecond-laser processing parameters (i.e., pulse energy and focusing depth) on track morphology have been investigated in detail. Based on analysis of track morphology and design of waveguide configurations, the telecom-band depressed-cladding waveguides have been successfully produced. It has also been found that, by increasing pulse energy for waveguide fabrication, telecom-band mode modulation from single-mode to multi-mode could be realized. The confocal micro-Raman (mu-Raman) spectroscopy indicates that original properties of SK1310 glass could be well preserved in waveguide cores. This work paves a way to fabricate telecom-band depressedcladding waveguides in SK1310 glass, having potential applications in integrated photonics and quantum optics.

Asteroids offer valuable insights into the formation and evolution of the solar system. Understanding their rotation and shape is essential for studying asteroid collision histories and geological processes, as well as for planning exploration missions. The conventional shape-from-silhouette (SFS) method reconstructs an asteroid’s rotation and shape using multiple resolved silhouette images captured at different rotational states. However, this method relies solely on silhouette information and is affected by the inherent shape symmetries, leading to ambiguities in rotation and shape model inversion. This paper presents an approach that integrates SFS and optical flow techniques for optimized asteroid rotation and shape modeling. In our approach, an optical flow method revealing information on asteroid motion and structure is integrated with the SFS technique to realize effective optimization. Additionally, a swarm intelligence-based strategy relying on parallel exploration and dynamic step adjustment is used to enhance global optimization. Experiments based on data from two typical asteroids, Itokawa (asymmetric shape) and Bennu (symmetric shape), demonstrate the promising performance of the proposed method. The results show that the approach achieves unique and accurate pole estimations from distances of several hundred kilometers, even under varying illumination conditions. Additionally, it can generate unique and precise shape models when favorable illumination conditions are present. For the asymmetric asteroid Itokawa, the maximum distance that allows for pole and shape inversion is approximately twice that of the symmetric asteroid Bennu. The proposed method can support scientific research on asteroids, such as their dynamics and morphology, as well as asteroid exploration missions.

Femtosecond laser processing enables large‐scale precise fabrication of micro/nanostructures on silicon surface demonstrating exceptional potential for integrated optoelectronic applications. Herein, a hybrid fabrication strategy combining ion implantation with femtosecond laser plasmonic nanolithography is developed. By leveraging localized surface plasmon resonance effect of embedded Ag nanoparticles in silicon (Ag NPs: Si), high‐precision color printing and self‐assembled nanostructures formation at an ultralow energy threshold (≈0.01 J cm 2 ) are achieved. Systematic control of laser parameters allows precise manipulation of Ag NPs, regulating the size and spatial distribution, which overcomes the inherent nonlinear absorption limitation of silicon. Raman spectroscopy reveals enhanced Ag–Si interface coupling induced in the laser‐treated locations, providing critical insights into optimization of laser‐driven nanoscale interactions. This study establishes an approach to optical response modulation and carrier mobility engineering in Ag NPs: Si, which contributes to the preparation of multifunctional integrated devices such as structured color displays, high‐density optical storage, and optoelectronic sensors.

A topological bound state in the continuum (TBIC) is a novel topological phase that has attracted significant attention. Different from conventional topological insulators (TIs), where boundary states reside within gaps, TBICs can support unconventional boundary states that remain isolated from the surrounding bulk states. In this work, we experimentally demonstrate multiple TBICs in photonic bilayer trimer lattices using femtosecond laser writing technology. By modulating the interlayer coupling between two trimer chains, we observe the emergence of two distinct types of TBICs. Moreover, we experimentally achieve the coexistence of in-gap topological states and TBICs and demonstrate the transformation between them. Our work unveils new insights into the flexible construction of TBICs, and this method can be easily applied to other one-dimensional topological structures, offering promising avenues for further research.

Ultrafast laser-excitation of lithium niobate (LiNbO3) crystal has triggered numerous photonic applications through the structural transitions in LiNbO3. However, the explanations for ultrafast laser-induced modification of LiNbO3 have remained phenomenological, lacking a convincing in-depth understanding of the fundamental laser-lattice interaction process. Based on ab initio simulations, it is demonstrated that photoexcited anharmonic phonons play a significant role in influencing the lattice structure of LiNbO3. Harnessing the real-time time-dependent density functional theory, it is revealed that the excitation of TO4 phonons via electric-phonon coupling triggers displacement-induced lattice oscillations during multiphoton ionization. These oscillations give rise to multistage structural strains, resulting in alterations of the refractive index. Significantly, these modifications exhibit sensitivity to the incident laser energy. Experimentally, using the waveguide technique and micro-Raman spectroscopy, the correlation between local refractive index, lattice volume density, and phonon vibrational modes has been established, exhibiting good consistency with theoretical predictions. This work provides an effective means to understand the ultrafast excitation of phonons and relaxation processes of the lattice in dielectric crystals. The transient evolution of the lithium niobate lattice under excitation of weak and strong optical fields is described by real-time time-dependent density functional theory simulation, and the lattice change from a contraction-expansion-Coulomb explosion is verified in the experiments. This work provides an effective means to realize micron-scale manipulation of dielectric crystals.image

We report on the design and fabrication of helical cladding waveguides in Nd:YAG crystal by using femtosecond laser direct writing. These circular cladding shapes waveguides are characterized through the end-face coupling at 1064 nm, possessing good guiding properties and low bending losses. The helical waveguide structure has a minimum bending loss of 0.55 dB/cm. The mode modulation has been achieved by altering helix geometry parameters. The polarization dependence of these waveguides is kept at a relatively low level. In addition, an S-bend waveguide has been fabricated, indicating that helical structure increases bending loss by enhancing the interaction between the light and boundaries. This study paves the way for the fabrication of photonic circuits with complex 3D structures in crystals.

[This corrects the article DOI: 10.1002/smsc.202200038.].

Plasmonic nanostructures have emerged as a critical component in broad fields ranging from optical modulation to biosensing and energy harvesting. Here, an ultrathin titanium (Ti) film (8 nm) is introduced between the gold (Au) film and fused silica (SiO2) substrate to facilitate energy deposition of the surface plasmon polariton (SPP) waves excited at the Ti/SiO2 interface under 1030 nm fs laser irradiation. The femtosecond laser-SPPs patterning results in the formation of Au nanoribbons with a width of about 270 nm and a spatial period of about 700 nm. Notably, centimeter-scale, self-assembled nanoribbons of high uniformity are achieved within several minutes. The localized surface plasmon resonance (LSPR) induced absorption peak is measured at the near-infrared band, confirming the high quality of the fabricated plasmonic nanostructures. Our findings suggest that the femtosecond laser-SPPs patterning technique represents a promising approach for the rapid and cost-effective production of large-scale plasmonic nanostructures.

Light manipulation of metallic nanoparticles (NPs) with outstanding plasmonic properties attracts broad interest in multiple areas owing to the significant field enhancement and localization effect mediated by plasmons. So far, optical migration of NPs has only been achieved on platforms such as gases, solutions, and mesoporous thin films (TiO2), while not been realized for NPs inside large macroscopic transparent materials due to the high density and viscosity of a host matrix. The high localization of light intensity by plasmons allows the laser pulses to deposit energy via near-field at the nanoscale at reduced thermal modification and ablation over extended regions inside a host material. This makes it possible to achieve directed and guided migration of NPs within large macroscopic transparent materials. Here, we propose a plasmon-enhanced method using ultrafast laser direct writing to manipulate metal NPs inside a glass. The optical potential between closely spaced NPs increases significantly under laser irradiation, leading to guided energy deposition by ionization, and light interference which leads to the self-assembly of NPs into nanostructures under irradiation of subsequent pulses. In this work, ordered subwavelength NP gratings are fabricated, which exhibit polarization dependence and show promise for applications in information encoding and optical storage. This study provides a new physical case for ultrafast laser-driven guided self-assembly of NPs, where the dynamic evolution via their fragmentation and migration is observed, contributing to the understanding of the origin of self-assembled gratings and opening up new research directions for light manipulation of NPs.

We report on an integrated 1 x 5 beam splitter based on optical waveguides with type I and type II modifications of femtosecond laser (fs-laser) writing in lithium tantalate (LiTaO3) crystal. The cladding waveguides consisting of type-II modified tracks are used for optical signal transmission, photon crosstalk reduction, and mode field regulation. The single-line waveguides with type I modification are utilized for light beam splitting. Type-I single-line waveguides are with relatively weak thermal stability, which are utilized to produce a recoverable and rewritable optical beam splitter, and the structure still possesses good transmission properties after the reconstruction. Especially, the type-I modified waveguides can be rewritten in very short time (1-2 min). The beam splitter shows good performance in outputting programmable optical signals, which provides a possible strategy for the development of erasable photonic data processors.

Quantum tunneling is considered the cornerstone of many physical processes. So far, its evolution over time, especially under an external field superimposed on the periodic potential field, has not been directly observed experimentally due to the harsh requirements and extremely short time scale. In this paper, we fabricate twisted photonic lattices consisting of three-dimensional waveguide arrays and experimentally illustrate the optical tunneling process under the parabolic potential field through the photonic route. Optical tunneling inhibition is observed experimentally, and the reduced time required to achieve the maximum transfer of waveguides indicates the inhibition can be modulated by the parabolic potential. This provides a reliable means for subsequent experimental study of quantum tunneling under complicated external potential field.

We report on the frequency doubling properties of femtosecond (fs) laser direct-written lithium triborate (LBO) cladding waveguides. The guiding properties (mode profiles and propagation losses) of these waveguides are experimentally characterized. The maximum conversion efficiency values of 4.8% and 8.6% are achieved for frequency doubling processes of 1064 -> 532 nm and 1560 -> 780 nm, respectively, in the fabricated depressed-cladding waveguides at room temperature. Our results suggest the potential applications of fs-laser direct writing technique as well as LBO waveguides in constructing compact frequency converters.

Plasmon‐based devices have founded numerous applications in photonics based on optically excited strong near‐field effect at nanoscale. So far, the large‐area fabrication of periodic plasmonic nanostructures is still challenging due to a small write‐field limitation of lithography‐based techniques, especially for metallic substrates. A novel strategy is proposed to fabricate millimeter‐sized patterns of periodic plasmonic nanostructures inside dielectric materials (glass) through a femtosecond laser direct‐write plasmonic nanolithography approach. Noble metal nanoparticles are formed by the ion implantation in glass and reshaped into a nanowire‐like nanoparticles’ assembly by direct writing with femtosecond laser harnessing plasmonic interaction. As‐designed patterns at nanoscale are inscribed by this type of plasmonic lithography to form wires composed of nanoparticles. Examples for applications, the linear dichroism response, and structural color have been achieved by the plasmonic nanogratings buried inside glass (i.e., at subsurface regions). The work opens a new avenue to manipulate metallic nanoparticles in solids by direct plasmonic nanolithography and offers a reliable implementation of large‐area fabrication of plasmonic nanostructures for diverse range of photonic applications.

We report for the first time on optical waveguides in zinc oxide (ZnO) crystals fabricated by femtosecond laser direct writing. The confocal Raman microscopy under 488 nm laser excitation is used to investigate the micro-modifications of the laser irradiation, and guiding properties are studied via the end-face coupling at 632.8 nm. The mode modulation has been achieved by the adjustment of laser writing parameters. A minimum propagation loss of ∼6 dB/cm is obtained for the double-line waveguide structures. A Y-branch waveguide beam splitter is also fabricated, reaching a splitting ratio of nearly 1:1. The original optical properties in the guiding region have been well preserved, according to the confocal Raman investigation, which suggests potential applications of the ZnO waveguides for integrated photonics and nonlinear optics.

Device-free human activity recognition based on WiFi signals has become a very popular research field. However, it still has one major problem that is activities of “unseen” humans cannot be accurately classified, which makes it infeasible in real-world application. To tackle this issue, in this paper, we present a human activity recognition (HAR) system based on identity (ID) transfer mechanism named CrossID, which can cross the boundaries of identity by taking the high-level personal characteristics of the source domain and target domain as IDs for training and transferring. Specifically, we employ the margin-based loss function to improve the training speed and accuracy. To fully evaluate the feasibility of the proposed approach for human activity recognition, a variety of the data samples have been taken at 16 locations conducted by six people performing four different types of activities. Through extensive experiments on our dataset, we verify the effectiveness, robustness, and generalization ability of proposed system. Our average recognition rate in the target domain is 95%, which is slightly lower than 98% in the source domain.

We report on a novel waveguide-based polarization beam splitter (PBS) fabricated by femtosecond (fs) laser in lithium niobate (LiNbO3) crystals. This monolithic PBS is composed of tailored waveguide configurations with different guiding properties in which linearly polarized light along extraordinary refractive index (n(e)) and ordinary index (n(o)) can be well separated. At the wavelength of 1064 nm, polarization extinction ratio (PER) can reach to 16.60 dB and 16.18 dB for n(e) and n(o) polarizations, with insertion loss (IL) of 3.86 dB and 4.15 dB respectively. Our work may pave a new way for designing high-performance PBS and creating compact polarization conversion systems in integrated photonics and quantum photonics.