Silicon-based photodetectors are experiencing significant demand for realizing infrared photodetection, night vision imaging, and ultraviolet-enhanced monitoring and communication. Recently, femtosecond-laser (fs-laser) hyperdoped silicon photodetectors have gained attention as promising alternatives to conventional silicon-based devices, owing to their exceptional properties, including high detectivity at low operating bias, broadband response spectrum beyond the bandgap limitation, wide operational temperature range, and ultrahigh dynamic range. Despite these advantages, the practical application of fs-laser hyperdoped devices has been hindered by challenges such as uneven surface structures and numerous lattice defects, which impede industrialization, chip integration, and ultraviolet photodetection performance. In this study, we present, to our knowledge, a novel design of flat fs-laser hyperdoped silicon materials and photodetectors tailored for complementary metal-oxide-semiconductor (CMOS) compatibility. A key innovation lies in the reduction of surface structure dimensions by three orders of magnitude, enabling the integration of fs-laser hyperdoped silicon as a photodetection layer in back-illuminated CMOS devices. The proposed photodetector achieves a peak responsivity of 120.07 A/W and a specific detectivity of 1.27 × 1014 Jones at 840 nm, marking the highest performance reported for fs-laser hyperdoped silicon photodetectors. Furthermore, it demonstrates ultraviolet enhancement and sub-bandgap infrared photodetection simultaneously, with responsivities exceeding 10 A/W across a broad spectrum from 350 to 1170 nm at 5 V. This breakthrough not only paves the way for fs-laser hyperdoped silicon in array photodetection but also facilitates its integration with silicon-based chip fabrication processes, addressing critical bottlenecks for industrialization and advancing the field of silicon photonics.

Polymer-embedded liquid crystals (LCs) play a pivotal role in smart applications, enabling precise tunability over electro-optical properties. However, high energy consumption in conventional LC-polymeric systems limits their efficiency in sustainable and environmental protection technologies. Reducing driving voltage without compromising mechanical and electro-optical performance remains an unresolved challenge. Here, we demonstrate a polymer-confined ferroelectric nematic (NF) liquid crystal system, polymerized with mesogenic and non-mesogenic monomers under an electric field. The effective multidomain polymer structure exploits the intriguing properties of the NF LC and generates a highly scattered state with an excellent contrast ratio in the NF phase. Electric field-controlled reorientation of directors leads to a transparent state at a very small voltage. The system demonstrates the advantages of a low driving voltage, sub-millisecond switching time with negligible hysteresis, and improved durability, promoting applications in energy-saving smart windows. This work reveals valuable insights into leveraging NF LCs and tailoring polymer networks to advance the performance of electro-optic devices.

The growing demand for broadband near-infrared (NIR) irradiation in security, biomedicine, and food science is driving the development of new NIR light sources. Herein, a series of Cr3+/Ni2+ co-doped transparent glass ceramics containing octahedrally coordinated KCdF3 nanocrystals have been successfully prepared. Under 450 nm blue light excitation, the combination of Cr3+ and Ni2+ results in an ultra-broadband NIR emission band ranging from 700 to 1800 nm. Based on the excitation and emission spectra and the decay lifetime curves, the energy transfer (ET) efficiency from Cr3+ to Ni2+ is confirmed to be 50.2%. A glass ceramic-converted NIR-LED was fabricated by integrating a commercial blue LED chip with a representative Cr3+/Ni2+ co-doped glass ceramic and has demonstrated potential applications in the areas of covert information recognition and night vision illumination. Our investigation provides new insights into the development of ultra-broadband NIR light sources that are both cost-effective and efficient.

Gallium oxide (Ga2O3), a promising candidate in ultraviolet photodetection, suffers significant limitations in its optoelectronic performance owing to the challenge of achieving p-type doping. To address this challenge, we designed a type-I heterostructure photodetector (PD) by depositing two-dimensional Bi films on Ga2O3 using the pulsed laser deposition technique. Under the illumination intensity of 0.1 µW/cm2, this PD exhibits a remarkable responsivity of up to 200 mA/W and a detectivity of 8.58 × 1011 Jones, demonstrating its excellent low-light detection ability. In addition, due to the built-in electric field of the heterojunction, the device can effectively suppress the dark current and has the performance of self-powered detection.

This study aims to investigate the anisotropic properties of Pr:YAP on (100), (010), and (001) crystal planes. Raman spectroscopy shows anisotropy in vibrational modes, but absorption spectra display no significant anisotropy. X-ray excited luminescence (XEL) and photoluminescence (PL) spectra reveal anisotropy in Pr3+ and F+ luminescence intensities. The PL decay time (∼7 ns) indicates similar luminescence mechanisms. The anisotropic defect distribution observed in thermoluminescence analysis can be explained using areal ion density and the offset parameter of Al atoms. Ultimately, it is inferred that shallow-level defects compete with Pr3+ ions, leading to variations in anisotropic luminescence intensity.

Ge2Sb2Se4Te1, a newly developed phase change material derived from Ge2Sb2Te5, has garnered significant interest among researchers due to its numerous advantages. Here, its phase change characteristics under the electron beam evaporation method are thoroughly investigated, and a layered tunable color structure is proposed. Based on the low intrinsic absorption of Ge2Sb2Se4Te1 material, it exhibits excellent dynamic tunability along with vivid color appearance including high brightness and high purity. In experiments, five representative colors—red, green, blue, yellow, and purple—were successfully prepared. The peak reflection of these samples averaged 92%, and when heated to 320°C, the temperature at which the phase transition of Ge2Sb2Se4Te1 occurred, reflection loss was barely observed. In addition, after phase transition, the sideband reflection at non-target wavelengths decreased by 30%, bringing high-purity crystalline-state colors and noticeable color changes. Therefore, it is believed that the structural color scheme proposed here will contribute to the development of many fields including smart glasses, artificial retinal devices, high-resolution displays, and beyond.

Modulating photoluminescent (PL) materials is crucial for applications such as super-resolution microscopy. The combination of PL materials and photoswitches can achieve this aim by utilizing isomerization of the photoswitches. Here we report an optically PL switchable system by mixing carbon quantum dots (CQDs) and diarylethene (DAE) molecular photoswitches. The PL on/off states of CQDs, switched with alternating visible and UV light, achieve a PL on/off ratio of ∼500 and stable reversibility over 20 cycles. The mechanism of our design is revealed by PL lifetime measurements, temperature-dependent PL spectroscopy, and density functional theory (DFT) calculations, confirming that efficient static quenching and the inner filter effect between CQDs and closed DAEs are the keys to achieving such outstanding performance.

An optical communication system based on the pulsed laser with a GHz repetition rate and multi-wavelength operation enables an increase in data transmission rate and data capacity. We propose a novel hybrid cavity with a single-mode fiber/multi-mode fiber/single-mode fiber (SMF-MMF-SMF) configuration for a GHz ultrafast laser with multi-wavelength operation. The length of each section is elaborately designed to reduce the transmission loss between the SMF and MMF, as well as to limit its total length to under 10 cm. By adopting the proposed hybrid cavity, the >1 GHz-repetition-rate fiber laser operation with four wavelength peaks is demonstrated, showing a signal-to-noise ratio of 90 dB. Furthermore, great tunability in spectra by manipulating the launched cavity parameters is also proved. To the best of our knowledge, this is the first realization of multi-wavelength operation among the GHz lasers using the SMF-MMF-SMF cavity architecture. The finding might provide a new opportunity for large-capacity high-speed optical communication systems.

We propose a promising method to develop flexible, compact, and tunable light-activated film diffractive optical elements (FDOEs) with exceptional diffraction efficiency, by integrating liquid crystal (LC) geometric phase-based diffractive optical elements (DOEs) with a specifically designed light-activated LC polymer (LCP) film. Arbitrary film bending induced by UV/Vis irradiation is realized through precise mesogens arrangement within the LCP film, enabling 1D and 2D beam steering, as well as dynamic and reversible switching between structured and Gaussian lights after cooperating with the DOE design. Furthermore, remarkable fatigue resistance, solvent resistance, and thermal stability are demonstrated, providing a solid material platform for advanced optical applications.

Zinc sulfide (ZnS) has promising linear and nonlinear optical properties and has shown important applications in military and modern devices. In this work, coupled with the chemical vapor deposition (CVD) method and hot isostatic pressing (HIP), we successfully grew a high-transmittance and low-absorption-coefficient polycrystalline ZnS with a size of 1 m × 2 m and a thickness of 20 mm. The linear optical properties, including the UV-vis-NIR transmission spectrum, infrared spectrum, and refractive index, were systematically characterized, which shows that the present ZnS polycrystal exhibits a wide transmission range from 0.34 to 15.00 µm, covering two important atmospheric windows. Moreover, its Sellmeier equation was achieved and fitted as a modification of previous studies. According to the refractive index and transmission spectrum, optical loss was calculated to be < 3.5% from 1 to 10 µm. All the results indicate that the present sample has comparable properties with the single crystals and should have potential applications as a functional material.

Optical modulation is significant and ubiquitous to telecommunication technologies, smart windows, and military devices. However, due to the limited tunability of traditional doping, achieving broadband optical property change is a tough problem. Here, we demonstrate a remarkable transformation of optical transmittance in few-layer graphene (FLG) covering the electromagnetic spectra from the visible to the terahertz wave after lithium (Li) intercalation. It results in the transmittance being higher than 90% from the wavelengths of 480 to 1040 nm, and it increases most from 86.4% to 94.1% at 600 nm, reduces from ∼80% to ∼68% in the wavelength range from 2.5 to 11 µm, has ∼20% reduction over a wavelength range from 0.4 to 1.2 THz, and reduces from 97.2% to 68.2% at the wavelength of 1.2 THz. The optical modification of lithiated FLG is attributed to the increase of Fermi energy (Ef) due to the charge transfer from Li to graphene layers. Our results may provide a new strategy for the design of broadband optical modulation devices.

The existing single-crystal slicing techniques result in significant material wastage and elevate the production cost of premium-quality thin slices of crystals. Here we report (for the first time, to our knowledge) an approach for vertical slicing of large-size single-crystal gain materials by ultrafast laser. By employing aberration correction techniques, the optimization of the optical field distribution within the high-refractive-index crystal enables the achievement of a continuous laser-modified layer with a thickness of less than 10 µm, oriented perpendicular to the direction of the laser direction. The compressed focal spot facilitates crack initiation, enabling propagation under external forces, ultimately achieving the successful slicing of a Φ12 mm crystal. The surface roughness of the sliced Yb:YAG is less than 2.5 µm. The results illustrate the potential of low-loss slicing strategy for single-crystal fabrication and pave the way for the future development of thin disk lasers.

Electron-trapping materials, due to their exceptional ability of energy storage and controllable photon release under external stimulation, have attracted considerable attention in the field of optical information storage (OIS). In this work, Gd3Al3Ga2O12:Ce3+, Yb3+ fluorescent ceramics, were developed using air and vacuum sintering technology. By co-doping Ce3+ and Yb3+, the trap density was significantly increased by 7.5 times compared to samples containing only Ce3+. Vacuum annealing further enhanced trap density by 1.6 times compared to samples sintered solely in air, while generating deep traps (1.44 eV), making Gd3Al3Ga2O12:Ce3+, Yb3+ an excellent OIS medium. This work is expected to facilitate the development of OIS materials.

Cholesteric liquid crystal (CLC) has been widely used in flat optical elements due to the Pancharatnam–Berry (PB) phase modulation. In order to achieve PB phase modulation for both circular polarizations, it is natural to come up with stacking CLCs with opposite chirality. Here, various optical properties of diverse CLC stacking structures are systematically investigated by numerical calculations. With the thickness of the CLC sublayers becoming smaller, the reflection bandgap splits into three main parts, and the rotatory dispersion gradually becomes negligible. Vector beams provide a more intuitive verification. These results provide theoretical guidance for future studies on stacked chiral anisotropic media.

Topological nodal-line semimetals attract growing research attention in the photonic and optoelectronic fields due to their unique topological energy-level bands and fascinating nonlinear optical responses. Here, to the best of our knowledge, we first report the saturable absorption property of topological nodal-line semimetal HfGeTe and the related pulse modulation in passively Q-switched visible lasers. Few-layer HfGeTe demonstrates outstanding saturable absorption properties in the visible-light band, yielding the saturation intensities of 7.88, 12.66, and 6.64 µJ/cm2 at 515, 640, and 720 nm, respectively. Based on an as-prepared few-layer HfGeTe optical switch and a Pr:LiYF4 gain medium, Q-switched visible lasers are also successfully achieved at 522, 640, and 720 nm. The minimum pulse widths of the green, red, and deep-red pulsed lasers are 150, 125.5, and 420 ns, respectively. Especially for the green and red pulsed laser, the obtained pulse width is smaller than those of the low-dimensional layered materials. Our work sheds light on the application potential of topological nodal-line semimetals in the generation of visible pulsed lasers.

Curvature sensing plays an important role in structural health monitoring, damage detection, real-time shape control, modification, etc. Developing curvature sensors with large measurement ranges, high sensitivity, and linearity remains a major challenge. In this study, a curvature sensor based on flexible one-dimensional photonic crystal (1D-PC) films was proposed. The flexible 1D-PC films composed of dense chalcogenide glass and water-soluble polymer materials were fabricated by solution processing. The flexible 1D-PC film curvature sensor has a wide measurement range of 33–133 m-1 and a maximum sensitivity of 0.26 nm/m-1. The shift of the transmission peak varies approximately linearly with the curvature in the entire measurement range. This kind of 1D-PC film curvature sensor provides a new idea for curvature sensing and measurement.

The fundamental understanding of exciton physics and the anisotropic behavior of excitons and charge carriers in perovskite materials are pivotal to controlling the orientation of emission dipoles and the polarization of photocurrents to enhance the efficiency of light-emitting diodes (LEDs) and polarization photodetectors. However, it is not easy to clarify these fundamental physics and optoelectronic properties in traditional inorganic 3D perovskite polycrystalline thin films. Here, we found three narrow emission peaks with one broad peak from neutral excitons at 78 K in hybrid perovskite PEA2PbI4 single crystals. The out-of-plane electric field can induce the dissociation of the excitons with a larger decrease in the emission intensity of the exciton with a higher out-of-plane component. Moreover, the photocurrent can be greatly increased up to a maximum of 11 times with the tuning of excitation polarization from 90° to 0°. These results deepen our understanding of the anisotropic exciton and charge carrier physics of perovskite materials to promote the development of highly efficient LEDs and polarization photodetectors.

Toroidal multipole is a special current distribution that has many different characteristics from electric multipole and magnetic multipole distributions. Because of its special properties, the toroidal dipole is a research hotspot in the field of metamaterials and nanophotonics. However, the low scattering of the toroidal dipole moment makes its excitation a challenging task. At present, there are relatively few studies on its specific engineering applications. In this paper, by slotting in the rectangular cavity, the excitation of an equivalent toroidal dipole is successfully achieved over a wide frequency range of 53–58 GHz. Results indicate that under the action of the toroidal dipole, the TE10 mode electromagnetic waves transmitted in the rectangular waveguide are converted into vector beams and are radiated outwards. Further adjusting the spatial distribution of the magnetic dipoles in the toroidal dipoles yields results that indicate that the resonance mode in the slot is still dominated by the magnetic toroidal dipole moment, and the electromagnetic waves radiating outward are vortex beams carrying vector polarization. The scattered energy of each dipole moment inside the antenna is calculated. This calculation verifies that the mass of the vector beam and vector vortex beam is closely related to the toroidal dipole supported by this antenna. The proposed structure can be applied to explorations in vortex filtering, in photon entanglement, and in the photonic spin Hall effect.

Scintillators are the vital component in X-ray perspective image technology that is applied in medical imaging, industrial nondestructive testing, and safety testing. But the high cost and small size of single-crystal commercialized scintillators limit their practical application. Here, a series of Tb3+-doped borosilicate glass (BSG) scintillators with big production size, low cost, and high spatial resolution are designed and fabricated. The structural, photoluminescent, and scintillant properties are systematically investigated. Benefiting from excellent transmittance (87% at 600 nm), high interquantum efficiency (60.7%), and high X-ray excited luminescence (217% of Bi4Ge3O12), the optimal sample shows superhigh spatial resolution (exceeding 20 lp/mm). This research suggests that Tb3+-doped BSG scintillators have potential applications in the static X-ray imaging field.

We demonstrate an all-polarization-maintaining (PM) passively mode-locked Yb3+-doped fiber laser (YDFL) with a fundamental repetition rate of 1.3 GHz. The optical spectra of a linearly polarized soliton exhibit different shapes by rotating the fast axis of the fiber optical pigtail of a dispersive dielectric mirror. The oscillator provides a series of laser performance, such as a threshold pump power for continuous wave laser oscillation of 3.1 mW, an optical-to-optical efficiency for mode-locking of 29%, and an integrated relative intensity noise of 0.08%. To the best of our knowledge, this is the first report of >1 GHz ultrafast all-fiber YDFL with PM architecture.

Ga2O3-based avalanche photodetectors (APDs) have gained increasing attention because of their excellent photoelectric conversion capability in the UV solar-blind region. Integrating high-quality epitaxial Ga2O3 with p-type semiconductor remains an open challenge associated with the integration difficulty on alleviating its defects and dislocations. Herein, we construct an APD consisting of epitaxial β-Ga2O3/La0.8Ca0.2MnO3 heterostructure. The pn junction APDs exhibit a high responsivity of 568 A/W as well as an enhanced avalanche gain of up to 3.0×105 at a reverse bias voltage of 37.9 V. The integration capability demonstrated in this work provides exciting opportunities for further development of high-performance Ga2O3-based electronics and optoelectronics.

Rare-earth-doped upconversion (UC) materials are ideal candidates for solar photovoltaic conversion and NIR response devices due to their unique spectral conversion properties. However, their low efficiency remains a tremendous challenge for practical applications. Here, we constructed an efficient NIR light-responsive device by coating a Si-photoresistor with a transparent gel consisting of UC powders and an organic polymer matrix. We show that reasonable introduction of alkali metal ions (Na+, K+, and Cs+) into the lattice of UC crystals results in the improvement of photoelectricity conversion efficiency, due to the high crystallinity and surface reconstruction caused by alkali metal ion doping.

Dysprosium-doped orthorhombic yttrium aluminate (Dy:YAlO3 or Dy:YAP) single crystals were grown by the Czochralski method with a size of Φ43 mm×150 mm. Based on the measurements of spectra and theoretical analysis, the white-light emission was investigated with different doping concentrations. The optimal white emission was achieved at Dy3+ doping concentration of 1.0% under 450 nm excitation. Combining with residual pumping light, the white-light output was successfully obtained with Commission Internationale de l´Eclairage (CIE) coordinates x=0.3797, y=0.3685, the color temperature of 4000 K, and the largest fluorescence quantum yield of 46.9%. With the development of the GaN laser diode, the Dy:YAP single crystal has proven applicable in white-light-emitting diodes.

Bismuth (Bi)-doped near-infared (NIR) glass that can cover the entire optical communication window (850, 1310, and 1550 nm) has become the subject of extensive research for developing photonic devices, particularly, tunable fiber lasers and ultrabroadband optical amplifiers. However, the realization of highly efficient NIR luminescence from Bi-doped glass is still full of challenges. Notably, due to the co-existence of multiple Bi NIR centers in the glass, the origin of newly generated Bi NIR emission peaks at ∼930 and ∼1520 nm is still controversial. Here, we report a new Bi-doped nitridated germanate glass with tunable ultrabroadband NIR emission (850–1700 nm) and high external quantum efficiency (EQE) of ∼50%. A series of studies, including spectral analysis, nuclear magnetic resonance (NMR), and others, provide powerful evidence for the mechanism of luminescence enhancement and tunability, and make reasonable inferences about the origin of the new emission bands at ∼930 and ∼1520 nm. We believe that the results discussed above would enrich our understanding about multiple Bi NIR emission behaviors and contribute to the design and fabrication of highly efficient Bi-doped ultrabroadband wavelength-tunable optical glass fiber amplifiers and lasers in the future.

Sb-doped &beta;-Ga2O3 crystals were grown using the optical floating zone (OFZ) method. X-ray diffraction data and X-ray rocking curves were obtained, and the results revealed that the Sb-doped single crystals were of high quality. Raman spectra revealed that Sb substituted Ga mainly in the octahedral lattice. The carrier concentration of the Sb-doped single crystals increased from 9.55&times;1016 to 8.10&times;1018 cm-3, the electronic mobility depicted a decreasing trend from 153.1 to 108.7 cm2 &middot;V-1 &middot;s-1, and the electrical resistivity varied from 0.603 to 0.017 &Omega;&middot;cm with the increasing Sb doping concentration. The un-doped and Sb-doped &beta;-Ga2O3 crystals exhibited good light transmittance in the visible region; however, the evident decrease in the infrared region was caused by increase in the carrier concentration. The Sb-doped &beta;-Ga2O3 single crystals had high transmittance in the UV region as well, and the cutoff edge appeared at 258 nm.

ZnGeP2 (ZGP) crystals have attracted tremendous attention for their applications as frequency conversion devices. Nevertheless, the existence of native point defects, including at the surface and in the bulk, lowers their laser-induced damage threshold by increasing their absorption and forming starting points of the damage, limiting their applications. Here, native point defects in a ZGP crystal are fully studied by the combination of high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and optical measurements. The atomic structures of the native point defects of the Zn vacancy, P vacancy, and Ge-Zn antisite were directly obtained through an HAADF-STEM, and proved by photoluminescence (PL) spectra at 77 K. The carrier dynamics of these defects are further studied by ultrafast pump-probe spectroscopy, and the decay lifetimes of 180.49, 346.73, and 322.82 ps are attributed to the donor Vp+ → valence band maximum (VBM) recombination, donor GeZn+ → VBM recombination, and donor–acceptor pair recombination of Vp+ → VZn-, respectively, which further confirms the assignment of the electron transitions. The diagrams for the energy bands and excited electron dynamics are established based on these ultrahigh spatial and temporal results. Our work is helpful for understanding the interaction mechanism between a ZGP crystal and ultrafast laser, doing good to the ZGP crystal growth and device fabrication.

Controlling architecture of hierarchical microstructures in liquid crystals (LCs) plays a crucial role in the development of novel soft-matter-based devices. Chiral LC fingerprints are considered as a prospective candidate for various applications; however, the efficient and real-time command of fingerprint landscapes still needs to be improved. Here, we achieve elaborate rotational fingerprint superstructures via dual photopatterning semifree chiral LC films, which combine the photoalignment technique and a dynamic light patterning process. An intriguing spatial-temporal rotational behavior is presented during the patterning of chiral superstructures. This work opens new avenues for the applications of chiral LCs in soft actuators, sensing, and micromanufacturing.

A kind of optical data storage medium based on electron-trapping materials, Y3Al5O12:Ce3+ fluorescent ceramic, was developed by vacuum sintering technology. The medium shows sufficiently deep traps (1.67 and 0.77 eV). The properties of trap levels were researched by thermoluminescence curves, and the optical storage mechanism based on Ce3+ ion doping was proposed. More importantly, the data can be written-in by 254 nm UV light, and readout by heating (300°C). This work expands the application fields of fluorescent ceramics, and it is expected to promote the development of electron-trapping materials.

Perovskite-structured barium strontium titanate (Ba1-xSrxTiO3, x = 0.1–0.9) films have been epitaxially fabricated by using a pulsed-laser deposition technique. The third-order nonlinear optical properties were studied through a z-scan method, allowing the resolution of the nonlinear refractive and absorptive contributions to the responses. Although all the samples show almost the same value of nonlinear absorption coefficient, the extracted nonlinear refractive index of the sample of x = 0.3 is apparently larger than that of other samples. Dependency of the nonlinear optical properties on the Ba/Sr ratio is discussed in terms of the crystal phase transformation and metal-oxygen bond length of the selected materials.

We designed a femtosecond (fs) + picosecond (ps) double-pulse sequence by using a Mach–Zehnder-like apparatus to split a single 120 fs pulse into two sub-pulses, and one of them was stretched to a width of 2 ps by a four-pass grating system. Through observing the ripples induced on the ZnO surface, we found the ionization rate appeared to be higher for the sequence in which the fs pulse arrived first. The electron rate equation was used to calculate changes of electron density distribution for the sequences with different delay times. We suggest that using a temporally shaped fs+ps pulse sequence can achieve nonlinear ionization control and influence the induced ripples.

A simple quasi-distributed fiber sensing interrogation system based on random speckles is proposed for weak fiber Bragg gratings (WFBGs) in this work. Without using tunable lasers or spectrometers, a piece of multimode fiber is applied to interrogate the WFBGs relying on the wavelength sensitivity of speckles. Instead of the CCD sensor, an InGaAs quadrant detector serves as the receiver to capture the fast-changing speckle patterns. A supervised deep learning algorithm of the multilayer perceptron architecture is implemented to process speckle data and to interrogate temperature changes or dynamic strains. The proposed demodulation system is experimentally demonstrated for WFBGs with 0.1% reflectivity. The experimental results demonstrate that the new system is capable of measuring temperature change with an accuracy of 1°C and achieving dynamic frequency of 100 Hz. This speckle-based interrogation system paves a new way for distributed WFBGs sensing with a simple design.

We developed a general framework for parallel all-optical logic operations with independent phase control of arbitrary orthogonal polarization state enabled by a single-layer metasurface. A pair of orthogonal circular polarized bases are used as two input channels of the logic operator, and their four combinations perfectly match various binary input states. Correspondingly, distinct phase profiles are encoded into the metasurface, which enables parallel operation of the two logic gates by way of polarization switching. It allows for an efficient and compact way to implement multi-channel multiplexed logic gate operations with the capability of fast optical computing at the chip scale.

Flexible devices provide advantages such as conformability, portability, and low cost. Paper-based electronics offers a number of advantages for many applications. It is lightweight, inexpensive, and biodegradable, making it an ideal choice for disposable electronics. In this work, we propose a novel configuration of photodetectors using paper as flexible substrates and amorphous Ga2O3 as the active materials, respectively. The photoresponse characteristics are investigated systematically. A decent responsivity yield and a specific detectivity of up to 66 mA/W and 3×1012 Jones were obtained at a low operating voltage of 10 V. The experiments also demonstrate that neither the twisting nor bending deformation can bring obvious performance degradation to the device. This work presents a candidate strategy for the application of conventional paper substrates to low-cost flexible solar-blind photodetectors, showing the potential of being integrated with other materials to create interactive flexible circuits.

Zeolitic imidazolate framework-8 (ZIF-8), a metal-organic framework (MOF) with a non-centrosymmetric crystal structure, exhibits nonlinear optics (NLO) properties and can act as the nanoporous matrix of guest molecules. Amorphization of ZIF-8 can be achieved by pressure or high temperature. Both crystalline and amorphous states have their inherent features for optical applications. The effects of the crystalline-amorphous transition on the structural and optical properties under pressure were investigated in detail. Amorphization leads to the destruction of the ZIF-8 lattice structure, collapse of pores, and the change of spatial symmetry, which in turn alters the NLO properties of ZIF-8 and the luminescence properties of the guest Eu cations. Our results establish the structure–optical properties relationship in the amorphization process and provide new clues in designing novel MOFs optical materials.

We demonstrate the dynamic coloration of polymerized cholesteric liquid crystal (PCLC) networks templated by the “wash-out/refill” method in the presence of organic compounds. The reflection colors were modulated by two key approaches, that is, the injection of mutually soluble organic fluids into a microfluidic channel and the diffusion of volatile organic compounds (VOCs). The reversible tuning of reflected colors with central wavelengths between ∼450 nm and ∼600 nm was achieved by alternative injection of nematic liquid crystal E7 (nav = 1.64) and benzyl alcohol (n = 1.54) using syringe pumps. The fascinating iridescence with reflection centers from ∼620 nm to ∼410 nm was presented from the volatilization and diffusion of alcohol as a model VOC. Additionally, the flow velocity of fluid and the diffusion time were adjusted to explore the underlying mechanism for the dynamic coloration of cholesteric networks. This work is expected to extend the study of PCLCs as a dynamically tunable optofluidic reflector, visually readable sensor, or compact anti-counterfeit label in response to organic compounds.

Large-size Al3+/Nd3+ co-doped silica glass with 5000 ppm Nd3+ and 50,000 ppm Al3+ doping concentrations was prepared by the modified sol-gel method combined with high-temperature melting and molding technology. Electron probe micro-analyzer tests indicated that high doping homogeneity was achieved with this sample preparation method. The spectral properties of the Nd3+ ions were evaluated. Nd3+-doped silica fiber (NDF) with a core-to-clad ratio of 20/125 μm was drawn from the preform with the Al3+/Nd3+ co-doped silica glass as the core. In the laser oscillation experiment, a maximum output power of 14.6 W at 1.06 μm with a slope efficiency of 39.6% was obtained from the NDF pumped by a commercial 808 nm laser diode. To the best of our knowledge, this is the highest laser power reported for an NDF operated at 1060 nm and prepared by a non-chemical vapor deposition method. In the master oscillator power amplifier experiment, a maximum power of 16.6 W corresponding to a slope efficiency of 30.5% at 1061 nm was also demonstrated. The laser performance of the NDF exhibited the great advantages and potential of the modified sol-gel method in fabricating Nd3+-doped silica glass for a new type of NDFs like large mode area fibers and fibers with large diameter ratio of core/cladding.

Density of dislocations in the near-surface layer was investigated in X-cut LiNbO3 depending on thermal annealing in the temperature range of 400°C–600°C. A dynamic model of randomly distributed dislocations has been developed for LiNbO3 by using X-ray diffraction. The experimental results showed that the dislocation density of the near-surface layer reached the minimum at the thermal annealing temperature of 500°C, with the analysis being performed when wet selective etching and X-ray diffraction methods were used. We concluded that homogenization annealing is an effective technique to improve the quality of photonic circuits based on LiNbO3. The results obtained are important for optical waveguides, LiNbO3-on-insulator-based micro-photonic devices, electro-optical modulators, sensors, etc.

In this study, an excellent polarization optical crystal LiNa5Mo9O30 with wide transmission range and high laser damage threshold was researched in detail. The laser damage threshold of the LiNa5Mo9O30 crystal was measured to be 2.64 GW/cm2, which was the highest among polarized optical crystals. The birefringence in the range of 0.435–5 μm was larger than 0.14, while the wedge angle between 31.94° and 32.12° would satisfy the application in this waveband. The extinction ratio of the fabricated prism with the wedge angel of 31.09° was larger than 15,000:1. The results show that the LiNa5Mo9O30 prism is an excellent polarization device, especially in the mid-infrared range and high-power applications.

We report VOx/NaVO3 nanocomposite as a novel saturable absorber for the first time, to the best of our knowledge. The efficient nonlinear absorption coefficient and the modulation depth are determined by the Z-scan technology. As a saturable absorber, a passively Q-switched Nd-doped bulk laser at 1.34 µm is demonstrated, producing the shortest pulse duration of 129 ns at a repetition rate of 274 kHz. In the passively Q-switched Tm:YLF laser with the prepared saturable absorber, the shortest pulse duration was 292 ns with a repetition rate of 155 kHz. Our work confirmed the saturable absorption in VOx/NaVO3 for possible optical modulation in the near-infrared region.

The near-infrared (NIR) emitting wavelength-tunable Cr3+-doped barium gallate (BGO:Cr) persistent luminescence (PersL) phosphors with enhanced luminescence were reported. The emission wavelength of the BGO:Cr PersL phosphors was adjusted from 715 to 739 nm by varying the amount of Cr3+ and the ratio of Ga:Ba. Meanwhile, the luminescence intensity and afterglow of the BGO:Cr PersL phosphors were enhanced. BGO:Cr PersL phosphors exhibited UV excitation, LED light restimulation, PersL for more than 6 days, and excellent capability for information storage, which was expected to promote the development of cheap and wavelength-tunable PersL materials for practical applications.

An AgGeSbTe thin film is proposed as a negative heat-mode resist for dry lithography. It possesses high etching selectivity with the etching rate difference of as high as 62 nm/min in CHF3/O2 mixed gases. The etched sidewall is steep without the obvious lateral corrosion. The lithographic characteristics and underlying physical mechanisms are analyzed. Besides, results of X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy further indicate that laser irradiation causes the formation of Ge, Sb, and AgTe crystals, which is the basis of etching selectivity. In addition, the etching selectivity of Si to AgGeSbTe resist is as high as 19 at SF6/Ar mixed gases, possessing good etching resistance. It is believed that the AgGeSbTe thin film is a promising heat-mode resist for dry lithography.

With the rapid growth of optical communications traffic, the demand for broadband optical amplifiers continues to increase. It is necessary to develop a gain medium that covers more optical communication bands. We precipitated PbS quantum dots (QDs) and BaF2:Tm3+ nanocrystals (NCs) in the same glass to form two independent emission centers. The BaF2 NCs in the glass can provide a crystal field environment with low phonon energy for rare earth (RE) ions and prevent the energy transfer between RE ions and PbS QDs. By adjusting the heat treatment schedule, the emission of the two luminescence centers from PbS QDs and Tm3+ ions perfectly splices and covers the ultra-broadband near-infrared emission from 1200 nm to 2000 nm with bandwidth over 430 nm. Therefore, it is expected to be a promising broadband gain medium for fiber amplifiers.

Two-dimensional (2D) Sn-based perovskites are a kind of non-toxic environment-friendly emission material with low photoluminescence quantum yields (PLQYs) and enhanced emission linewidths compared to that of 2D Pb-based perovskites. However, there is no work systematically elucidating the reasons for the differences in the emission properties. We fabricate (BA)2SnI4 and (BA)2PbI4 having different defect densities and different exciton-phonon scattering intensities. We also reveal that 2D Sn-based perovskites have stronger exciton-phonon scattering intensity and higher defects density, significantly broadening the emission linewidth and accelerating the exciton relaxation process, which significantly reduces the PLQY of 2D Sn-based perovskites.

We propose a simple five-layer structure for creating red structural color, which has high color purity and high brightness. The design is based on the superposition of a silver substrate and multilayer silicon material. Absorption at the shorter wavelengths of the structure is effectively guaranteed, and reflection at the longer wavelengths is well enhanced. The red structural color has a peak reflectivity of 91% and a colorimetric purity of 0.9. Moreover, the designed structure displays angle-invariant performance up to 60°. This kind of structure scheme is environmentally friendly with low fabrication cost, and it can play an important role in a variety of fields, such as color displays and image sensors.

Four single crystals (Yb0.15Lu0.85xY0.85-0.85x)3Al5O12 (x = 0, 0.25, 0.5, 1) were grown by the Czochralski method. The correlation of the host atom Lu:Y ratios with the density and the luminescence properties were revealed. The density increases linearly with increasing of Lu3+ content, which will improve the gamma ray cut-off ability. The integrated intensity of the X-ray excited luminescence spectrum increases exponentially with the increasing Y:Lu ratio, while the decay time becomes even shorter with the increasing Lu3+ content. These results will provide a basis to balance the comprehensive properties to match different application requirements.

Large area and uniform monolayer MoS2 is of great importance for optoelectronic devices but is commonly suffering from rather weak photoluminescence. Here, by engineering the concentration profiles of gaseous chemicals through extra trace amounts of water, we demonstrate the uniform dendrite-type growth of monolayer MoS2 unraveled by spatially resolved fluorescence spectroscopy, which exhibits macroscopic monolayer flakes (up to centimeter scale) with photoluminescence intensity of orders of magnitude higher than conventional chemical vapor deposition monolayer MoS2. Both spectroscopic evidence and theoretical models reveal that the fast-fractal dendrite growth can be ascribed to the extra introduced water sources that generate sufficient aqueous gas around the S-poor regions nearby the central-axis zone, leading to highly efficient Mo sources transport, accelerated S atom corrosion nearby grain edges, and/or defect sites, as well as enhanced photoemission intensity. Our results may provide new insight for high throughput fabrication of MoS2 monolayers with high yield photoluminescence efficiency.

Different post-treatment processes involving the use of ammonia and hexamethyldisilazane (HMDS) were explored for application to 351 nm third harmonic generation SiO2 antireflective (3ωSiO2 AR) coatings for high power laser systems prepared by the sol-gel method. According to experimental analysis, the 3ωSiO2 AR coatings that were successively post-treated with ammonia and HMDS at 150°C for 48 h and again heat-treated at 180°C for 2 h (N/H 150 + 180 AR) were relatively better. There were relatively fewer changes in the optical properties of the N/H 150 + 180 AR coating under a humid and polluted environment, and the increase in defect density was slow in high humidity environments. The laser-induced damage threshold of the N/H 150 + 180 AR coating reached 15.83 J/cm2 (355 nm, 6.8 ns), a value that meets the basic requirements of high power laser systems.

In this article, we investigate the phenomenon of coherent perfect absorption (CPA) with bulk Dirac semimetal (BDS) thin film. CPA of BDS appears at the frequency of 43.89 THz with 0° phase modulation of two coherent input lights. Meanwhile, it shows that CPA can be realized under oblique incidence circumstances for both TM and TE polarizations. Moreover, the frequency of CPA can be adjusted by altering the thickness of BDS thin film, and the dynamic regulation of CPA can be realized by changing the Fermi energy. Finally, the peak coherent absorption frequency can be controlled by changing the degeneracy factor.

In this Letter, Ti–Si bilayer was deposited on white silk to achieve coloration of the silk. By controlling the thickness of the Ti layer and Si layer, the saturation and the hue of the color on the silk could be preciously modulated, respectively. The structural colors on the silk could cover the major colors in the International Commission on Illumination 1931 chromaticity diagram, and it exhibits good durability, which is demonstrated by rubbing and stretching treatments. The developed textile coloration method may provide an eco-friendly technology in the silk dyeing industry.

The article is devoted to the technology for obtaining optical ceramics of AgBr-TlI and AgBr-TlBr0.46I0.54 systems and manufacturing samples with different compositions. The new heterophase crystal ceramics are transparent without absorption windows in the spectral range from 1.0 to 60.0 μm. In the ceramics’ transparency spectra based on the AgBr-TlI and AgBr-TlBr0.46I0.54 systems fusibility diagrams, with an increase in the thallium halides mass fraction, as well as the replacement of the bromine ion with iodine, the maximum transparency shifts to a long infrared region.

Up-convertion (UC) perovskite Er3+-doped PbTiO3 (Er-PTO) nanoparticles with green and red emissions were synthesized via the hydrothermal method. The UC properties were manipulated by adjusting the concentration of Er3+ ions dopant. The green emission intensity was decreased as the doping concentration increased from 1% to 4% (mole fraction), whereas the red emission intensity was increased. The influences of Er3+ ions on the temperature-sensing performance were further investigated. The results demonstrated that Er-PTO nanoparticles with doping 1% Er3+ ions possessed a sensitivity of 3.1 × 10-3 K-1 at 475 K, presenting a high potential in optical heating devices.

Transparent paper is a kind of promising and environmentally friendly material. In this study, we show that transparent paper can be fabricated in an ultra-fast and low-cost way. This low-cost top-down method only takes three steps of cell separation, lignin removal, and cold pressing to obtain a high-quality transparent paper. The fabrication time is further reduced, and the resulted transparent paper shows high transparency up to 90.3%. The application as a substrate material for transparent and flexible electronic devices is demonstrated by emulating the printed circuit on the prepared transparent paper. This top-down method will greatly promote the market-oriented applications of transparent paper as an environment friendly material.

We report an interesting study of electric-field-induced transformation from a single domain ferroelectric state to the multiple domain ferroelectric state in a KTa1-xNbxO3 (KTN) crystal. Experimental results obtained using the confocal μ-Raman spectroscopy confirm the dynamic change of lattice structures induced by an external electric field. Furthermore, the dependence of relative permittivity on the applied voltage also indicates the transformation of ferroelectric states involving the processes of splintering, inversion, and re-formation of ferroelectric domains.

We proposed a periodic mid-infrared broadband chiral structure. Its unit cell consists of four indium tin oxide (ITO) helix subunits with different radii. The simulation results show that the flat-topped broadband circular dichroism (CD) can be achieved in the mid-infrared band by optimizing the parameters of helix structures. The simulation results also show that compared with the metallic (Ag and Au) helix structures, the ITO helix structure proposed exhibits evidently better broadband CD and optical activity, which provides a new idea for the design of broadband polarization state control devices in the mid-infrared band.

In this work, we proposed a feasible method to prepare the Bi/Al co-doped silica glass by using laser additive manufacturing technology. Bi was uniformly doped into the silica matrix. The hydroxyl content of the glass sample was measured to be 29.36 ppm. Using an 808 nm laser diode as the excitation source, a broadband near-infrared emission from 1000 to 1600 nm was obtained. The emission peak was centered at 1249 nm, and the corresponding FWHM was more than 400 nm. The results show that the laser additive manufacturing technology is promising to fabricate highly homogeneous Bi-doped core materials with broader emission band, which is beneficial to solving the communication capacity crunch and promotes the development of fiber communication in the upcoming fifth and sixth generation systems.