Search Results (48)

This study used time-of-flight secondary ion mass spectrometry (TOF-SIMS) to comprehensively analyze the elemental composition, ion distribution, and signal variations in potassium dihydrogen phosphate (KDP) crystals at various sputtering depths after laser irradiation. Positive ion mass spectra were employed to identify the characteristic ions K⁺, Ca⁺, Fe⁺, Si⁺, and P⁺. These ions were assigned to their corresponding chemical species. Large-area two-dimensional chemical mapping and maximum count/total count (MC/TC) analysis combined and showed clear depth-dependent trends; all detected ions had significantly higher MC and TC values at larger sputtering depths. At a depth of 1.3 nm, Fe-related and O-related ion signals exhibited overlapping localized hotspots, whereas Ca species showed ring-like enrichment at the edges of the damage pits. These changes are attributed to the laser-induced decomposition of KDP crystals, in which metal inclusions absorb laser energy, generate localized high temperature and pressure, and promote material ejection and ion redistribution. These findings provide direct experimental evidence for understanding laser-induced elemental redistribution in KDP crystals and offer useful guidance for further optimization of their performance. Full article

We used powder X-ray diffraction (XRD) and ac impedance spectroscopy to investigate the polymorphic phase transitions undergone by the MH₂PO₄ (M = Cs, K, Rb) proton conductor series upon heating. High-pressure methods used in conjunction with energy dispersive XRD enhanced by synchrotron radiation allowed us to isolate a pure cubic (superprotonic) RbH₂PO₄ (RDP) polymorph (at P = 1.2 GPa and T = 320 °C) and collect data of enough quality to Rietveld refine its crystal structure. Our data and analysis reveal that cubic RDP (Pm-3m, a = 4.76 ± 0.01 Å) is described by a unit cell where Rb and P atoms are in (0, 0, 0) and (0.5, 0.5, 0.5) positions, respectively, whereas O atoms are in (0.5, 0.234(5) 0.342(6)) positions having a multiplicity of 24 and an occupancy of 0.166. This results in dynamically disordered PO₄ tetrahedra that enables the superprotonic conduction in RDP, a mechanism like the one in the high-temperature cubic phase of the Cs-based compound CsH₂PO₄ (CDP). This is a notable behavior, as RDP and CDP are structurally different at room temperature—RDP is tetragonal (I-42d) and CDP is monoclinic (P2₁/m)—but following polymorphic modifications upon heating they both end up in superprotonic cubic phases that are isostructural to one another. On the other hand, we found that although the K-based phosphate KH₂PO₄ (KDP) has the same crystal structures as RDP at room and at intermediate temperatures, further heating does not lead to a cubic KDP phase. Overall, our results are significant from both the fundamental and applied perspective as superprotonic phosphates are promising materials for fuel cell electrolyte applications. Full article

Using the gel-grown method to control the morphology of crystals attracts extensive attention. Potassium dihydrogen phosphate (KDP) is a nonlinear optical crystal with a high laser damage threshold. Here, we studied the crystallization of KDP in silica gel. The kebab-like KDP crystals (multiple KDP crystals aligning along a straight line) were prepared in the silica gel. In situ observation revealed that the kebab-like crystals were obtained through secondary nucleations on preformed needle-like crystals. Further investigation revealed that the hydroxyl groups on the gel network have an important influence on the formation of kebab-like KDP crystals. The hydroxyl groups on the gel networks can form hydrogen bonds with the phosphoric acid group of the KDP crystal and hinder the growth of the prismatic KDP faces, which leads to the preformation of needle-like crystals. Additionally, the influence of the acetic acid concentration and antisolvent on morphology was also studied. Full article

To overcome the challenges of processing soft-brittle potassium dihydrogen phosphate (KDP) crystals, this study proposes a back-propagation (BP) neural network model for the rapid prediction of the ion beam removal function using Faraday cup scanning data (a method that measures the spatial distribution of ion beam current density). By correlating current density measurements with point etching experiment results, the model accurately maps both the linear relationship (R² = 0.98) between peak removal rate and peak current density, and the non-linear relationship between the full width at half maximum (FWHM) of the beam and the removal function. The predicted removal function demonstrates high accuracy, with a volume removal rate error of just 2.56% compared to experimental results. Furthermore, this method drastically reduces calculation time from approximately 2 h (required by the conventional point-etching experiment, which involves iterative vacuum cycling, etching, and ex situ interferometry) to just 2 min, significantly improving efficiency. Applied to the ion beam polishing of a 50 mm × 50 mm × 10 mm KDP crystal, the model proved highly effective. The surface figure error was corrected from an initial 0.298λ peak-to-valley (PV) and 0.0496λ root-mean-square (RMS) to 0.167λ PV and 0.036λ RMS, where λ (632.8 nm) is the wavelength of the He-Ne laser used for interferometric surface measurement, achieving a convergence ratio (defined as the ratio of initial PV to final PV) of 1.78. This research provides a high-efficiency, high-precision technical solution for manufacturing KDP components for inertial confinement fusion (ICF) applications. Full article

To address the issues of heat accumulation and potential thermal damage during radio-frequency (RF) ion beam machining of KDP crystals, an energy deposition model and a temperature field model were developed based on Sigmund’s sputtering theory, a Gaussian beam distribution model, and heat conduction theory. Combined with the Monte Carlo method, the effects of incident energy, incident angle, and ion species on the disturbed layer depth and sputtering yield were systematically investigated. Furthermore, the influences of beam divergence angle and deflection angle on the surface energy deposition density distribution were analyzed. On this basis, the evolution of the temperature field and thermal stress field in KDP crystals under both stationary and linearly moving Gaussian surface heat sources was numerically simulated. The results indicate that the proposed model can effectively characterize the thermal response during ion beam machining of KDP crystals. The disturbed layer depth, sputtering yield, and energy deposition density distribution exhibit pronounced sensitivity to processing parameters. Under a stationary heat source, significant local heat accumulation and stress concentration tend to occur on the material surface. In contrast, a moving heat source can mitigate excessive temperature rise at a single location to some extent, although it also produces a heat-affected zone extending along the scanning path. These findings provide a theoretical basis for the optimization of low-damage RF ion beam machining parameters for KDP crystals. Full article

Heavy precipitation in Northeast China is frequently modulated by the Northeast China Cold Vortex (NCCV), although the microphysical processes within squall lines under such conditions remain insufficiently understood. This study presents a comprehensive analysis of an NCCV-influenced squall line in Liaoning Province, utilizing coordinated S-band polarimetric radar and surface disdrometer observations. The raindrop size distribution (DSD) characteristics and three-dimensional microphysical structure are systematically examined for both convective and stratiform regimes. A comparative analysis of DSD and warm-rain microphysical mechanisms is also conducted with a Mei-yu event. Results show that convective rain in the NCCV squall line exhibits a continental-type DSD, characterized by fewer but larger raindrops compared to other heavy rainfalls in China. In contrast, the Mei-yu frontal convection under NCCV influence exhibits a transitional DSD pattern between the maritime and continental types, with raindrops smaller and denser than those in the NCCV squall line. Vertical structure of the mature squall line shows prominent differential reflectivity (Z_DR) and specific differential phase (K_DP) columns above the melting level within the convective region, indicating vigorous riming growth of graupel and hail driven by strong updrafts. Meanwhile, the stratiform region is characterized by ice crystals and aggregates, formed primarily through deposition and aggregation processes. The subsequent melting of ice-phase particles followed by collision–coalescence and evaporation-driven size sorting shapes the large but sparse raindrops in the NCCV squall line. Comparison with Mei-yu convection demonstrates that surface DSD is shaped by environmental conditions and vertical microphysics. The drier, more unstable environment in the NCCV squall line favors deep convection with active ice-phase processes, while the relatively moist and stable environment of the Mei-yu convection supports shallower convection dominated by warm-rain processes. Future multi-case studies with integrated observations are needed to quantify how environmental and aerosol conditions modulate these heavy precipitation processes. Full article

The Nd:GYSAG crystal enables multi-wavelength near-infrared laser output, with adjustable wavelengths tailored for specific application requirements, making it highly valuable for space-borne water vapor detection. This study reports, for the first time, the side-pumping characteristics and electro-optical Q-switching performance of this crystal. Using Ø3 × 73 mm and Ø4 × 73 mm crystal rods doped with 1.21 at.% Nd:GYSAG (chemical formula Nd_0.033Gd_0.93Y_1.79Sc_0.70Al_4.54O_11.99), 1060.4 nm laser output was achieved under 808 nm laser diode (LD) side-pumping at a repetition rate of 100 Hz and a pump pulse width of 250 μs. The experimental results show that the Ø4 × 73 mm rod had a higher laser threshold but exhibited significantly superior slope efficiency and maximum output power compared to the Ø3 × 73 mm rod. Using a flat–flat resonator, optimal laser performance was obtained with an output coupler transmission of 35%, yielding a slope efficiency of 37.2%. A maximum output energy of 179.4 mJ was achieved at a pump energy of 646 mJ. Thermal lensing effects were compensated using a flat–convex cavity, leading to improved laser performance and beam quality. Electro-optical Q-switching experiments were conducted using a KD*P crystal. A comparison between voltage-applied and voltage-removed Q-switching techniques revealed superior performance for the voltage-applied method. High-performance laser output was realized, achieving a maximum pulse energy of 59.6 mJ, a pulse width of 14.93 ns, and a peak power of 3.99 MW. This study provides an important foundation for the development of near-infrared laser devices based on Nd:GYSAG. Full article

In inertial confinement fusion (ICF) laser drivers, large-aperture high-intensity third-harmonic (3ω, central wavelength 351 nm) laser pulses passing through KDP crystals (potassium dihydrogen phosphate) can produce strong transverse stimulated Raman scattering (TSRS). TSRS not only depletes the energy of the 3ω laser beam but also damages the KDP crystal, thus significantly limiting the enhancement of ICF laser driver capabilities. Therefore, effectively suppressing TSRS in KDP crystals is a critical issue in the design and construction of ICF laser driver systems. This paper first proposes that SSD has the ability to suppress TSRS through theoretical analysis of the characteristics of SSD beams. Secondly, through numerical simulations, it presents the influence of variations in three key parameters—modulation amplitude, modulation frequency, and grating dispersion coefficient—on the TSRS gain. The results show that the Stokes gain decreases with increasing modulation amplitude and modulation frequency; specifically, the suppression capability of SSD for TSRS gradually strengthens as modulation bandwidth increases. In addition, previous reports have demonstrated that SSD can significantly suppress stimulated rotational Raman scattering (SRRS) in air, which highlights the potential value of applying SSD in large laser facilities such as ICF driver systems. Full article

The results of precise measurements of the temperature dependencies of quadratic electro-optic coefficients, namely $g_{1111}-g_{1122}$ and $n_{\mathrm{o}}^3{g}_{1111}-n_{\mathrm{e}}^3{g}_{3311}$, in KH₂PO₄ (KDP) and KD₂PO₄ (DKDP) crystals at a wavelength of 632.8 nm are presented. We consider electro-optic coefficients describing changes in the optical impenetrability tensor resulting from an applied electric field, as well as intrinsic electro-optic coefficients defined in terms of induced polarization. The results show significant differences in the values of the analogous coefficients for the KDP and DKDP crystals and their temperature dependencies. Therefore, the quadratic electro-optic effect in KDP-type crystals cannot be easily described based solely on the contribution of PO₄ tetrahedra, as assumed in current models of the linear effect. Moreover, the values of the intrinsic coefficients in the KDP and DKDP crystals differ even more than the corresponding usual electro-optic coefficients, which contradicts the conventional belief in their lower variability. Full article

Potassium dihydrogen phosphate (KDP) crystals, vital for high-power laser systems, pose significant machining challenges due to their brittleness, low hardness, and hygroscopic properties. Achieving crack-free, high-precision surfaces is essential but complex. Single-point diamond fly-cutting (SPDF) is the primary method, yet it exposes tools to high mechanical stress and heat, accelerating wear. In dry cutting, worn tools develop adhesive layers that detach, causing scratches and degrading surface quality. Traditional wet cutting improves surface finish but leaves residual fluids that contaminate the surface with metal ions, leading to optical degradation and fogging. To address these issues, this study explores mixed-fat-based minimum quantity lubrication (MQL) as a sustainable alternative, comparing two lubricants: biodegradable-base mixed ester lubrication (BBMEL) and hydrocarbon-based synthetic lubricant (HCBSL). A comprehensive evaluation method was developed to analyze surface roughness, tool wear, and subsurface damage under dry cutting, MQL-BBMEL, and MQL-HCBSL conditions. Experimental results show that MQL-BBMEL significantly enhances machining performance, reducing average surface roughness by 27.77% (Sa) and 44.77% (Sq) and decreasing tool wear by 25.16% compared to dry cutting, outperforming MQL-HCBSL. This improvement is attributed to BBMEL’s lower viscosity and higher proportion of polar functional groups, which form stable lubricating films, minimizing friction and thermal effects. Structural analyses confirm that MQL-BBMEL prevents KDP crystal deliquescence and surface fogging. These findings establish MQL-BBMEL as an eco-friendly, high-performance solution for machining brittle optical materials, offering significant advancements in precision machining for high-power laser systems. Full article

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 the crystal structure and properties of KDP crystals have been investigated by using first-principles calculations. Theoretical calculations show that Al³⁺ ions mainly replace K sites in KDP crystals and could complex with intrinsic V_H⁻ point defects to form Al_K²⁺ + 2V_H⁻ cluster defects. The linear absorption spectra indicate that the presence of Al³⁺ ions has minimal impact on the linear absorption of KDP crystals, aligning well with the experimental findings. And Al³⁺ ions could cause a slight shortening of the band gap of KDP crystals. However, these ions could bring significant deformations of O-H bonds. As the concentration of Al³⁺ ions increase, more O-H bonds linking to PO₄ groups are distorted in KDP crystals. As a result, the structural instability could be fast enhanced with increasing the defect concentration. Therefore, high concentrations of Al³⁺ ions could cause the instability of the crystal structure, which finally affects the laser-induced damage resistance of the KDP crystals. This manuscript contributes to a more comprehensive understanding of the physical mechanisms by which different impurity ions affect the optical properties of KDP crystals. Full article

In this paper, we investigate the theory of energy distribution when divergent light undergoes harmonic conversion in KDP crystals, and based on this theory, we design and construct a precision measuring instrument for the detuning angle of (KDP) Crystals (MIDC). The device can obtain the detuning angle of the crystal by a single measurement with an average measurement error of 72.78 urad. At the same time, it also has the function of scanning the full aperture of the crystals. Using the MIDC, it is possible to quickly measure the KDP crystal at a single point and quickly scan the crystal detuning angle at full aperture. In addition, we conduct a theoretical study on the variation of detuning angle caused by gravity-influencing factors under online conditions, propose an optimization formula for the offline measurement results of detuning angle, and calculate the optimized values of detuning angle for two kinds of crystals under 45° online conditions. We finally study the error source of the MIDC device, analyze the trend of the influence of positioning errors of the crystal and optical elements on the detuning angle measurement results, and provide theoretical support for the error monitoring and correction of MIDC. Full article

The structure of an aqueous solution of potassium dihydrogen phosphate (KH₂PO₄, KDP) was studied by small-angle X-ray scattering (SAXS) and molecular dynamics (MD). According to SAXS data, the octameric species (KH₂PO₄)₈ are formed in solution in addition to K⁺, (H₂PO₄)⁻, and KH₂PO₄, while the presence of other types of oligomers is not observed. When the temperature drops below the saturation temperature (~60 °C), the volume fraction of octamers increases sharply, reaching 50% at 4 °C. The results of MD calculations of the temporal stability relationships of dimers (KH₂PO₄)₂, tetramers (KH₂PO₄)₄, and octamers (KH₂PO₄)₈ show that the dimers and tetramers disintegrate rapidly (50–100 ps), while the octamers remain stable. A comparative analysis of the bonds between the octamers and the KDP crystal lattice was carried out when the octamer was inserted during crystal growth in the directions [001] and [100]. The possible relationship of the obtained results with the changes in the anisotropy of growth rates (habitus) of KDP crystals at different degrees of supersaturation is discussed. Full article

The focus of this study was to examine antisolvent effects, which hold significance in particulate processes, such as crystallization and precipitation. In the first section, an experimental investigation revealed that C₁–C₄ primary alcohols significantly reduced the solubility of potassium dihydrogen phosphate (KDP) in water. The solid–liquid equilibria of KDP solutions were determined using an innovative polythermal method, demonstrating time and labor efficiency compared to the traditional isothermal method while maintaining solubility determination quality. This achievement established an efficient tool for high-throughput solvent screening, a crucial aspect of particulate process development. In addition to the experimental approach, in the second part, the influence of these alcohols on KDP solubility was analyzed using the eNRTL thermodynamics model. The model’s estimated parameters confirmed that the addition of these alcohols induced strong non-ideal behavior in the solutions, altered interactions between solute species and solvent components, and reduced KDP solubility. Under the effects of these alcohols, KDP solubility generally increased with the length of the alkyl chain in the added alcohols, although methanol deviated from this observation. Furthermore, the present work also discussed the limitation of the well-known Bromley’s equation, particularly when applied for KDP in alcohol–water mixed solvents. Consequently, binary and ternary systems consisting of KDP, water, and C₁–C₄ primary alcohols were successfully modeled using eNRTL. Furthermore, it was determined that the obtained model was insufficient for quaternary systems with a higher alcohol content, particularly when high-order interactions were neglected as in the cases of binary and ternary systems. In short, these investigated alcohols have potential for future applications in the design of particulate processes, with a particular emphasis on antisolvent crystallization. Full article

Potassium dihydrogen phosphate (KDP) has garnered considerable attention due to its diverse applications across various scientific and engineering domains. Although promising machining performance enhancements have been achieved in ultra-precision diamond cutting, the brittle–ductile transition (BDT) depth for KDP crystals is essentially at the nanometer range and limits the further improvement of machining efficiency. In this paper, a novel ultra-precision diamond cutting process based on tool trapezoidal modulation is proposed for the first time to investigate the BDT characteristics of KDP crystals. By intentionally designing the tool modulation locus, the uncut chip thickness and cutting direction in the cutting duty cycle are kept constant, which provides a new strategy for probing the BDT mechanism and enhancing the machining performance. The BDT depth is significantly increased compared to the conventional ultra-precision diamond cutting owing to its unique modulation machining advantages. The significance of this paper lies not only in the improvement of the machining efficiency of KDP crystals through the proposed modulation cutting process, but also in the possibility of extending the relevant research methods and conclusions to the machining performance enhancement of other brittle optical crystals. Full article