Xian Zhao

Shandong University | SDU · State Key Laboratory for Crystal Materials

The borate crystal Zn4B6O13 (ZBO) exhibits excellent optical properties and exceptional thermal stability. In this study, large-sized ZBO and Ni-doped ZBO (Ni: ZBO) single crystals were grown using the Kyropoulos...

Monocrystalline graphene growth has always been an intriguing research focus. Argon (Ar) is merely viewed as a carrier gas due to its inert chemical properties throughout the whole growth procedure by the chemical vapor deposition method. In this work, the influence of Ar on temperature and flow fields was investigated in consideration of its physi...

The fundamental shear horizontal (SH0) guided wave transducer shows unique promise for non-destructive testing and structural health monitoring in oil pipelines, railway tracks, solar power plants, and beyond due to its non-dispersive characteristics. Under this background, it is desirable to explore the high-performance piezoelectric crystals to d...

Correlations existing between spectral components in multi-wavelength lasers have been the key challenge that hinders these laser sources from being developed to chaotic comb entropy sources for parallel random bit generation. Herein, spectrotemporally uncorrelated multi-order Stokes/anti-Stokes emissions are achieved by cooperatively exploiting no...

High-temperature piezoelectric vibration sensors play a crucial role in the accurate monitoring of the dynamic mechanical conditions in aerospace, automotive, and energy generation systems. However, the use of conventional piezoelectric materials in high-temperature environments is restricted owing to their limited Curie temperatures. In this study...

X‐ray detection has drawn great attention in industrial examination, medical imaging, scientific research, and beyond. Herein, the anisotropic X‐ray detection performances are investigated based on a novel oxide crystal KCsMoP2O9 (KCMP). The large dielectric screening effect and 1D infinite chain structure consisting of MoO6 octahedron and two PO4...

Cr³⁺ ions are impurity cations that lower the laser-induced damage threshold of crystals. Herein, the stability of Cr³⁺ cluster defects and their effects on crystal structure, electronic structure and optical properties were examined by DFT and UV-Vis spectroscopy. Two stabilizing CrK²⁺ + 2VH⁻ cluster configurations were constructed using first-pri...

We propose a multimode fiber laser sensor utilizing PI-SMF (polyimide-coated single mode fiber) for low-error relative humidity (RH) measurement, which is temperature compensated based on FBG. The PI-SMF in the laser cavity is used as a sensing element, and its length varies with humidity and temperature by volume-variation induced strain, which le...

Intentionally adding select ions such as Al3+ could be helpful in controlling the crystal habit of KDP crystal for high yield of optics. The study of how Al3+ ions affect crystal quality can provide a basis for selecting an appropriate doping level without negatively affecting the optical properties of crystals. Here, the influence of Al3+ ions on...

Graphene that is prepared by chemical vapor deposition (CVD) can realize the regulation of a monocrystalline layer with an arbitrary thickness through multilayer transfer method. This approach has significant advantages and potential for application in the membrane materials of extrinsic Fabry-Pérot interference (EFPI) optical fiber sensors. In thi...

The development of ultrasonic‐guided wave sensors is of great significance for structural health monitoring (SHM). In this work, a shear horizontal (SH) ultrasonic guided wave sensor based on the Ca3TaGa3Si2O14 (CTGS) piezoelectric single crystal is demonstrated. The findings reveal that the CTGS‐based ultrasonic guided wave sensor is proficient in...

Commercial polyimide-coated single-mode fiber (PI-SMF) with excellent water affinity properties has shown great potential in realizing robust and efficient humidity sensing. In this article, relative humidity (RH) sensing utilizing a passively mode-locked fiber laser (MLFL) combined with a beat frequency demodulation system is proposed and experime...

Infrared ship detection is of great significance due to its broad applicability in maritime surveillance, traffic safety and security. Multiple infrared sensors with different spectral sensitivity provide enhanced sensing capabilities, facilitating ship detection in complex environments. Nevertheless, current researches lack discussion and explorat...

We report on the continuous-wave (CW) and, for what we believe to be the first time, passively mode-locked (ML) laser operation of an Yb³⁺-doped YSr3(PO4)3 crystal. Utilizing a 976-nm spatially single-mode, fiber-coupled laser diode as pump source, the Yb:YSr3(PO4)3 laser delivers a maximum CW output power of 333 mW at 1045.8 nm with an optical eff...

Lithium niobate (LN) is a multifunctional crystal with excellent piezoelectric properties, making it a potential candidate for piezoelectric sensing applications. In this study, the mechanism of the discrepancies of piezoelectric...

We report on a diode-pumped SESAM mode-locked Yb:YSr 3 (PO 4 ) 3 laser generating soliton pulses as short as 61 fs at 1062.7 nm with an average power of 38 mW at ~66.7 MHz.

We present a dual-channel resonance acoustic sensor based on a poly (vinylidene fluoride-co-trifluoroethylene) piezo-electric membrane which combines the Fabry-Pérot interference and piezoelectric effects. The deformation of circular thin films is indicated by interference and piezoelectric effects at the same time, and the noise level was decrease...

In this study, a broadband high-sensitivity fiber-optic acoustic sensor with simple structure and low cost based on Brillouin random fiber laser (BRFL) is proposed and demonstrated theoretically and experimentally. A double coupler fiber ring resonator (DCFRR) in the BRFL, which filters out redundant random modes and ensures high-quality lasing out...

High‐temperature vibration sensors are of great importance for accurate monitoring of dynamic mechanical conditions in automotive, aerospace and energy‐generation‐related systems. Currently, piezoelectric crystals with ultrahigh operational temperature and good piezoelectric performance for high‐temperature sensing applications are attracting consi...

Due to ever‐increasing concerns about safety issues in using Li ionic batteries, solid electrolytes have extensively explored. The Li‐rich anti‐perovskite Li3OBr has been considered as a promising solid electrolyte candidate, but it still suffers challenges to achieve a high ionic conductivity owing to the high intrinsic symmetry of the crystal lat...

A resonant acoustic wave detector combined with Fabry–Pérot interference (FPI) and piezoelectric (PE) effects based on a polyvinylidene fluoride (PVDF) piezoelectric film was proposed to enhance the ability of the sensor to detect acoustic signals in a specific frequency band. The deformation of circular thin films was indicated by the interference...

A frequency comb generator (FCG) based on dual-cavity Brillouin random fiber lasing oscillation in the 1.5 μm telecon spectral window is established and experimentally demonstrated. In the half-open main cavity of the dual cavity, the stimulated Brillouin scattering in highly nonlinear fiber (HNLF) and Rayleigh scattering in single-mode fiber are e...

In this paper, a modified infrared and visible image registration method based on contour feature is proposed. Our method firstly extracts the feature contour and eliminates sparkling waves contour of the sea surface, determines the main direction of the contour based on the contour image, then uses the improved Scale Invariant Feature Transform (S...

High temperature detection is a constant challenge for condition monitoring under harsh environments in optical fiber sensors research. In this study, the temperature response characteristics of guided acoustic wave Brillouin scattering (GAWBS) spectra in silica single-mode fiber (SMF) up to 800 °C are experimentally investigated, demonstrating the...

Increasing the crystal resistivity is critically important for enhancing the signal-to-noise ratio and improving the sensing capability of high-temperature piezoelectric sensors based on langasite-type crystals. The resistivity of structural ordered langasite-type crystals is much higher compared to that of the disordered crystals. Here, we selecte...

The oxygen vacancy, hydrogen vacancy and potassium vacancy are the common intrinsic point defects in the potassium dihydrogen phosphate (KDP) crystals and can combine to form cluster defects. In this...

Large size and high quality single crystal is the prerequisite to fully evaluate the physical properties and potential technical applications. Herein, centimeter-sized KCsMoP 2 O 9 (KCMP) crystal was successfully grown by the...

An optomechanically mode-locked fiber laser (MLFL) temperature sensor based on forward stimulated Brillouin scattering (FSBS) is presented. By taking advantage of the mode selection function of FSBS, longitudinal modes matched with the acoustic resonance frequency in FSBS are effectively enhanced to achieve a near-single longitudinal mode output wi...

The laser induced damage sites on the surface of KDP crystal component tend to grow with the subsequent laser irradiation, which substantially decrease the lifetime of these optics. The structural...

A highly-sensitive acoustic sensor based on low-noise narrow-linewidth Brillouin random fiber laser with DCFRR is proposed and demonstrated for detecting short- and long-range acoustic signals in the range of 2Hz~200kHz with high signal-to-noise ratios.

The intrinsic n-type of epitaxial graphene on SiC substrate limits its applications in microelectronic devices, and it is thus vital to modulate and achieve p-type and charge-neutral graphene. The main groups of metal intercalations, such as Ge and Sn, are found to be excellent candidates to achieve this goal based on the first-principle calculatio...

Surface defects are usually associated with the formation of other forms of expansion defects in crystals, which have an impact on the crystals’ growth quality and optical properties. Thereby, the structure, stability, and electronic structure of the hydrogen and oxygen vacancy defects (VH and VO) on the (100) and (101) growth surfaces of KDP cryst...

Guided-wave-based structural health monitoring (SHM) technology is of great importance for real-time inspection of high-temperature structures. The fundamental shear horizontal (SH0) wave is believed to be an ideal wave mode for developing SHM systems due to its nondispersive characteristics. However, currently very limited SH0 wave transducers can...

Cu step beams (CSBs) are common products obtained when growing graphene by chemical vapor deposition (CVD), which markedly affects the quality of graphene. Although considerable progress has been made in the preparation of large-area graphene on Cu, the growth behavior of CSBs has not been fully understood. This study investigated the main factors...

A single-longitudinal-mode high-coherence Brillouin random fiber laser (BRFL) with low-noise and narrow linewidth is proposed and experimentally demonstrated, which owns the shortest cavity structure ever reported in BRFL configuration by the combined utilization of highly nonlinear fiber (HNLF) and unpumped Er-doped-fiber sagnac loop (UESL). In th...

Electrically controlled half-metallicity in antiferromagnets is of great significance for both fundamental research and practical application. Here, by constructing van der Waals heterostructures composed of two-dimensional (2D) A-type antiferromagnetic NiI 2 bilayer (bi-NiI 2 ) and ferroelectric In 2 Se 3 with different thickness, we propose that...

Defects are considered as one of the important factors affecting the quality and laser‐induced damage threshold of potassium dihydrogen phosphate (KH2PO4, KDP). In this study, hybrid density functional theory is used to investigate how the Zn2+ ions affect the properties of KDP crystal. Since crystal defects often do not exist singly but combine wi...

High-temperature measurements above 1000 °C are critical in harsh environments such as aerospace, metallurgy, fossil fuel, and power production. Fiber-optic high-temperature sensors are gradually replacing traditional electronic sensors due to their small size, resistance to electromagnetic interference, remote detection, multiplexing, and distribu...

Frequency upconversion technology with good performance including high sensitivity, fast response, and room-temperature operation is a promising method for terahertz-wave detection. The sum-frequency conversion and difference-frequency conversion jointly affect the detection ability for upconversion detection using organic crystals as nonlinear med...

A bulk Nd:LaCa4O(BO3)3 (Nd:LaCOB) single crystal with the low Nd³⁺-doping concentration (~0.5 at.%) was grown by Czochralski (Cz) method. Its powder X-ray diffraction, Nd³⁺ ions doping concentration, polarized transmittance and emission spectra, and fluorescence lifetimes were tested. Based on the Judd-Ofelt theory, the spectral parameters of Nd:La...

The development of high-temperature guided wave transducers for high-temperature structure health monitoring is of great interest in many aspects of industrial engineering. In this work, the zero-order shear horizontal (SH 0 ) guided wave transducer was designed and analyzed based on the X-plate from Ca 2 Al 2 SiO 7 (CAS) crystals. Furthermore, the...

A stabilized coherent narrow-linewidth Brillouin random fiber laser with low lasing noise is proposed and investigated experimentally, which employs stimulated Brillouin scattering and Rayleigh scattering in optical fibers to provide the gain and the random distributed feedback, respectively. The stabilized lasing output with suppressed noise is re...

A novel laser crystal Nd³⁺-doped yttrium barium phosphate (Nd:YBa3(PO4)3, hereafter Nd:YBP) with disordered crystal structure was reported. Single crystal growth, thermal, spectral and laser performances were investigated. The thermal conductivity at room temperature was found to be 1.35 W·m⁻¹·K⁻¹ and shown an increased tendency with increased temp...

Epitaxial graphene on SiC without substrate interaction is viewed as one of the most promising two-dimensional (2D) materials in the microelectronics field. In this study, quasi-free-standing bilayer epitaxial graphene (QFSBEG) on SiC was fabricated by H2 intercalation under different time periods, and the temperature-dependent Raman spectra were r...

Lithium niobate (LiNbO3, LN) is a kind of multifunctional crystal material. In this study, an optimum piezoelectric crystal cut (XZt/28°) with central resonance frequency of 150 kHz and stable electro-elastic...

The characteristics of potassium dihydrogen phosphate (KDP) crystals with the Cr(NO3)3 doping at ～10 ppm level were studied by the ultraviolet-visible (UV-Vis) absorption spectrum, electron paramagnetic resonance spectroscopy (EPR), and...

A low-noise Brillouin random fiber laser with narrow linewidth is realized by incorporating an unpumped Erbium-doped fiber loop which acts as a dynamic fiber grating capable of center-frequency auto-tracking, mode filtering, and lasing stabilization.

The Fe3+ ion is the most common impurity ions in potassium dihydrogen phosphate (KDP) and it can combine with hydrogen vacancies to form cluster defects which may lead to optical...

Centimeter-sized high quality Ca 2 Nb 2 O 7 crystals were successfully grown using the conventional Czochralski pulling method, and the relationship between the crystal structure and physical properties has been clearly explained.

The ocean connects all continents and is an important space for human activities. Ship detection with electro-optical images has shown great potential due to the abundant imaging spectrum and, hence, strongly supports human activities in the ocean. A suitable imaging spectrum can obtain effective images in complex marine environments, which is the...

In chemical vapor deposition, oxygen plays an important role during graphene growth, especially in the case of copper substrates. However, currently, there is inconsistent information on the role of oxygen in graphene growth. In this study, the mechanism of pre-oxidation on copper substrate to reduce the nucleation density was explored, and the eff...

The regulation of interfacial charge transfer, optimization of active sites, and maintenance of stability are effective strategies for improving catalytic performance. The effect of the oxygen vacancy (VO) and nitrogen doping on these parameters for CO2 photoreduction on Pd10/TiO2(101) was studied using density functional theory calculations. The r...

Rare-earth calcium oxyborate crystals (RECa4O(BO3)3, RECOB, RE: rare-earth elements) is a kind of multifunctional crystal materials. In this work, the temperature dependent behaviors of the electro-elastic constants for NdCOB crystal were investigated over the temperature range of –80–200 oC, and their temperature coefficients were evaluated. It is...

Lithium niobate crystals (LiNbO3, LN) are multifunctional crystal materials with many outstanding properties. In this work, the electro-elastic properties of LN single crystals were explored at temperatures from −150 °C to 150 °C. The temperature dependences of dielectric permittivities, elastic compliances, electromechanical coupling factors and p...