Potassium Dihydrogen Phosphate Crystals Research Articles

First-principles investigation on the structural, optical, and laser-induced damage characteristics of boron impurity and boron-oxygen defect cluster in potassium dihydrogen phosphate crystals

The DFT+U method combined with HSE06 hybrid functional and finite-size correction has been employed to investigate the defect formation energies, lattice modifications and optical spectra of Potassium Dihydrogen Phosphate (KDP) crystals with Boron. The B defects contain the B interstitials (Bi), the B substituted P sites (BP), and the boron-oxygen defect clusters ([BP+VO]). The results demonstrate that these B defects can trigger lattice distortions. The BP and [BP+VO] have a minor lattice change rate and greater stability, while Bi has a relatively large local distortion inducing crystal damage. We have also utilized conformational coordinate diagrams to explore the optical absorption/emission processes arising from B defects. The BP and [BP+VO] were found to generate absorption peaks at 330 nm and 255 nm, while the Bi leads to absorption peaks near the absorption edge. The absorption peaks within the near-ultraviolet range might have an energy buildup at the defects, which would decrease laser utilization and harm the crystal.

Influence of Ca-substituted K-induced cluster defects on the electronic structure and optical properties of KDP crystals

Compensation mechanism following Ca substitution in K sites was computed using GULP. Utilizing density functional theory for three charge states, the impact of defect clusters CaK + VK/CaK + VH on potassium dihydrogen phosphate (KDP) crystals in both phases was assessed. Corrections to the band edge and defect formation energies were made employing hybridization floods HSE06 and FNV. Neutral and −1 valence defect states emerged. Cluster defects induced pronounced lattice distortion in PE-KDP. Notably, PE-KDP exhibited an additional photoemission of 2.89 eV, signifying a substantial structural impact. Comparative stability analysis favored FE-KDP, offering theoretical guidance for KDP crystal utilization.

Investigation into “hair” inclusions in large-sized KDP crystals grown by traditional method

Potassium dihydrogen phosphate (KDP) crystals are widely used in high-energy laser facilities for harmonic generation. An important defect observed in KDP crystals, known as "hair" inclusions in large-size crystals grown by traditional methods, was investigated using ultra-microscopy. Most of the "hair" inclusions within the crystals have a straight chain structure, while only a few displays a curved formation. The "hair" inclusions consist of multiple liquid inclusions and exhibit a chain-like structure with quasi-periodic features. The size of these liquid inclusions varies, ranging from 17.54 to 56.90 μm, and show a chain density between 0.90 mm−1 and 20.77 mm−1. The angles of the "hair" inclusion orientations about the c-axis range from 30° to 79°, corresponding to the dislocations in KDP crystals. Furthermore, the study examined the impact of "hair" inclusions on the transmittance of the crystals. This investigation aims to enhance the understanding of “hair” inclusions in traditionally grown KDP crystals and attempts to clarify the factors leading to the formation of these inclusions. It also offers a theoretical and experimental basis for reducing these inclusions in KDP crystals.

Damage effects of KDP crystals induced by nanosecond laser

Abstract The surface morphology, compositions, microstructures, and chemical bond vibrations of potassium dihydrogen phosphate (KDP) crystals induced by nanosecond laser with different wavelengths, at different energy density are studied by scanning electron microscopy (SEM) and infrared spectroscopy (IR) techniques. SEM results showed that with the increase of laser energy density, the damage region on KDP surfaces presented three parts evidently. And the damage area increases nonlinearly with the laser energy density, accompanied by an increase in O element contents and a decrease in P and K element contents. Meanwhile, at the same energy density, the damage area induced by the 355 nm nanosecond laser is much larger than that by the 1064 nm nanosecond laser. Infrared spectrum results revealed that the laser irradiation leads to a break in hydrogen bonds and a dehydration of KDP crystals, in conjunction with a generation of P=O and P-H bonds. Moreover, with the increase of the laser energy density, the KDP crystal is damaged firstly, and then is annealed and repaired, finally is destroyed again. In addition, after irradiation at 10 J/cm2, all vibration modes of KDP crystals weaken or even disappear, and the sever damage occurs.

Influence of citric acid on optical properties of unidirectional grown potassium dihydrogen phosphate crystals

Influence of citric acid on optical properties of unidirectional grown potassium dihydrogen phosphate crystals

Enhancement of growth perfection and optical transmission in rhodamine B-doped KDP single crystal for photonic applications

In recent years, because of the rapid development persisting in the modern electronic industries, materials with the ability to produce highly efficient harmonic generation have acquired great demand as they are suitable for high-speed devices and the progressing field of optical communication systems. The present work reports the growth, diffraction and spectroscopic features of the pure and Rhodamine B (RB)-doped potassium dihydrogen phosphate (KDP) crystals. The crystals were grown by employing the conventional slow evaporation technique. The XRD and UV–visible spectral studies have been carried out to examine the structural and optical behavior of the grown crystals. An optical microscopic technique has been utilized to explore the surface features of the crystals. Based on the growth features and the observed analytical results, it is authenticated that the RB-doped KDP crystal possesses a better crystalline nature and optical transmittance than the pure KDP crystal thereby it is strongly suggested for the applications of photonic devices.

A novel slurry for atomic-scale polishing of KDP crystals

Abstract Atomic-scale surfaces and structures have been playing a significant role in the next generation of devices and products. Potassium dihydrogen phosphate (KDP) crystals are crucial in energy sectors but challenging for ultra-precision processing due to deliquescence, brittleness, and low hardness. This paper introduces a novel chemo-mechanical slurry designed for achieving atomic-scale polishing of KDP crystals. The slurry employs a combination of polyethylene glycol (PEG) and anhydrous ethanol (AE) to counter deliquescence. In addition, graphite oxide (GO) with KOH is incorporated to prevent the embedding of SiO2 abrasives and the dissolution of KDP in deionized water (DW). The mechanism underlying the formation of an ultra-smooth surface is elucidated based on the analysis of the X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) test. Response surface method (RSM) is used to optimize the slurry parameters and finally obtaining an atomic-scale surface with Sa 0.3 nm.

Insight into the damage mechanism of KH2PO4 crystals with BaK-SiP by hybrid density functional theory

The laser-induced damage threshold (LIDT) of potassium dihydrogen phosphate (KDP) crystals is one of the key factors affecting the application of KDP crystals for Inertial confinement fusion (ICF). Previous studies have found that Ba, Si impurities can form BaK-SiP defect complexes in KDP crystals. However, the microscopic nature of the defect complexes is still unclear. We precisely calculate defect formation energy (DFE) in various charge states (-1, 0, +1), configuration coordinate diagram (CCD) and optical spectra by hybrid density functional theory. We found BaK-SiP introduce two defect states in the band gap. In the transitions (BaK-SiP)✕+h∙→(BaK-SiP)∙ and (BaK-SiP)✕+e-→(BaK-SiP)′, excited state and ground state have an intersection point in the Marcus inverted region and the activation energies are nearly 0 eV. The results showed that the defect complexes could capture holes and electrons through lattice relaxation, causing significant heat deposition and resulting in crystal damage. This implies a new damage mechanism of KDP crystals is discovered.

Study of electrical properties of L-Cysteine-doped potassium dihydrogen phosphate crystals grown under the influence of electric field

Study of electrical properties of L-Cysteine-doped potassium dihydrogen phosphate crystals grown under the influence of electric field

Crystallization of KDP in the presence of 4-nitro benzoic acid, L-ornithine hydrochloride and terephthalic acid

The present study is to investigate the optical, thermal and SHG properties of grown potassium dihydrogen phosphate (KDP) crystals using slow evaporation method in the presence of 4-nitro benzoic acid, l-Ornithine Hydrochloride and Terephthalic acid. Powder crystal XRD studies confirm their structure as that of KDP. The presence of functional groups has been tested and confirmed by FTIR. UV–visible spectral analysis - Differential Reflectance Studies (DRS) is used to examine the optical properties of pure and doped KDP crystals within the wavelength range of 200–800 nm and also evaluate the band gap, refractive index, extinction coefficient and optical conductivity of the grown crystals. Thermal properties of grown crystal are analysed by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Second harmonic generation test is carried out for the grown crystals to analyse nonlinear optical (NLO) properties.

Optimal operating conditions for the rapid growth of KH2PO4 crystal by numerical simulation

Numerical simulations of the turbulent hydrodynamics and concentration in the rapid growth of potassium dihydrogen phosphate (KH2PO4 or KDP) crystals have been performed. In this work, a quadratic power-law growth model is applied, concerning the mass transfer occurring at the crystal surface during the growth process under low supersaturations. The mass transfer boundary condition is discretized by using the Over-Relaxed approach. The effects of the growth temperature and rotation rate on surface supersaturation distribution and the diffusion layer are investigated, which are critically involved in the processes of surface morphological instability and inclusion formation. Due to the kinetic limitation, the response of different types of crystal surfaces to temperature varies, with a pyramidal surface about twice as high as a prismatic face. In addition, the contour map of the growth rate combined with the coefficient of variation (C.V) for various temperatures and rotation rates is used. Uniformity of surface supersaturation is provided by lowering the growth temperature and increasing the rotation rate. Furthermore, the criteria of crystal growth strategies are proposed to optimize the process parameters and obtain favorable conditions for crystal growth, thereby facilitating defect-free and high-quality crystal formation at an appropriate growth rate.

Investigation of elastoplastic deformation in potassium dihydrogen phosphate crystals through nanoindentation and ultra-precision fly cutting experiments

Investigation of elastoplastic deformation in potassium dihydrogen phosphate crystals through nanoindentation and ultra-precision fly cutting experiments

Growth, strain, energy gap, optical, mechanical, piezoelectric, and morphology analyses of 2-methylimidazole (2MI) single crystal for NLO device fabrication

2-methylimidazole (2MI) single crystal has been successfully grown by slow evaporation solution technique (SEST) by using water as a solvent. The synthesized 2MI crystal was purified by repetitive recrystallization. Various other characterizations were carried out for the grown 2MI single crystal, such as powder X-ray diffraction (PXRD), FTIR, UV–Visible NIR, Microhardness, Photoluminescence, SEM, Piezoelectric, and SHG. The 2MI crystal was subjected to PXRD to endorse the crystalline quality of the material. The vibrational assignments and their functional groups were identified from the FTIR analysis. The UV–Visible NIR study exposes the transparency and cut-off wavelength of the 2MI crystal. The mechanical strength was investigated by Vickers microhardness tester. The surface investigation of the 2MI crystal was analyzed by a scanning electron microscope technique to obtain the presence of defects and surface texture in the developed 2MI crystal. The photoluminescence spectrum confirmed the green light emission of the crystal. The value of the piezoelectric d[Formula: see text] coefficient is measured using piezoelectric analysis. Kurtz powder’s second harmonic generation test reveals that the frequency conversion efficiency of 2MI is 3.7 times higher than that of potassium dihydrogen phosphate (KDP) crystal.

Effect of THz-bandwidth incoherent laser radiation on bulk damage in potassium dihydrogen phosphate crystals

The laser-damage performance characteristics of potassium dihydrogen phosphate (KDP) samples under exposure to a distinctive broadband incoherent laser pulse are investigated. A laser system providing such pulses is intended to explore improved energy-coupling efficiency on the target in direct-drive inertial confinement fusion experiments and provides incoherent bandwidths as large as 10 THz in a nanosecond pulse. A consequence of this bandwidth is very rapid fluctuations in intensity capable of reaching maxima much larger than the average intensity within the pulse. A custom damage-test station has been built to perform measurements with broadband incoherent pulses in order to determine what effect these fast and high-intensity oscillations have on laser damage. A set of experiments under different bandwidth and beam configurations shows the effect to be minimal when probing bulk damage in KDP. Modeling indicates this behavior is supported by long electron-relaxation times compared to the source-field fluctuations, following excitation of individual electrons in the conduction band. The results help better understand the laser-induced–damage mechanisms in KDP, and its ability to operate in broadband temporally incoherent high-energy lasers that may be particularly suitable for future laser-fusion energy systems.

Characteristics of broadband OPCPA based on DKDP crystals with different deuterations for the SEL-100 PW laser system.

We present the performances of a broadband optical parametric chirped pulse amplification (OPCPA) using partially deuterated potassium dihydrogen phosphate (DKDP) crystals with deuteration levels of 70% and 98%. When pumped by a Nd:glass double frequency laser, the OPCPA system using the 98% deuterated DKDP crystal achieves a broad bandwidth of 189 nm (full width at 1/e2 maximum) from 836 nm to 1025 nm. For the DKDP crystal with length of 43 mm, the pump-to-signal conversion efficiency reaches 28.4% and the compressed pulse duration is 13.7 fs. For a 70% deuterated DKDP crystal with a length of 30 mm, the amplified spectrum ranges from 846-1021 nm, the compressed pulse duration is 15.7 fs, and the conversion efficiency is 25.5%. These results demonstrate the potential of DKDP crystals with higher deuteration as promising nonlinear crystals for use as final amplifiers in 100 Petawatt (PW) laser systems, supporting compression pulse duration shorter than 15 fs.

Quantitative identification of deposited energy in UV-transmitted KDP crystals from perspectives of electronic defects, atomic structure and sub-bandgap disturbance

The laser-induced damage threshold (LIDT) of ultra-precision machined potassium dihydrogen phosphate (KDP) crystal is always lower than the intrinsic threshold.

Effect of deuterium content on the structural, optical, and thermal properties of DKDP crystals: a systematic analysis.

Deuterated potassium dihydrogen phosphate (DKDP) crystals with different deuterium contents have a wide range of applications, such as frequency conversion in high power lasers, electro-optic modulation, and Q-switching crystals for Pockels cells. However, there is a lack of systematic research on the effect of deuterium content on the fundamental structure and properties of these DKDP crystals. To this end, in this study, a series of DKDP crystals with different deuterium contents have been grown using the "point-seed" rapid growth method, and the structure and properties of the crystals have been characterized. The results indicate that as the deuterium content increases, the cell parameter along the a(b)-axis direction gradually increases, and the transmittance gradually increases in the infrared range. A small amount of doping (low H or D ratio) reduces the structural integrity of the crystal, and the crystals at intermediate deuterium concentrations have better crystallinity. The thermal properties of the crystals do no change significantly with the variation in the deuterium content. Overall, these findings can serve as a useful reference for boosting the application of DKDP crystals with various deuterium contents.

Effect of Organic Entities on the Performance of Potassium Dihydrogen Phosphate (KDP) Crystals

The 0.5mol l-cystine and 2mol oxalic acid doped in potassium dihydrogen phosphate crystals have been developed by slow evaporation method at room temperature. The structural properties of the grown crystal were analyzed by powder X-ray diffraction technique. The functional groups of grown crystals were successfully identified using FTIR spectral analysis. The optical transparency of the grown crystals is examined in the range of 200-900 nm using UV-visible studies. The optical transmittance is found to be 87 % of the grown crystal. The energy band gap (Eg) of the grown crystal was calculated at 3 eV. The Kurtz- Perry test has been employed to determine the SHG efficiency and the SHG efficiency of the grown crystal was 0.5 % of pure KDP crystal tested by Kurtz-Perry powder technique.

Study of the surface damage threshold and mechanism of KDP crystal under ultrashort laser irradiation

Here, we investigate the mechanism of surface damage threshold anisotropy induced by ultrashort laser in potassium dihydrogen phosphate (KDP) crystal. Carrier-lattice nonequilibrium interaction is simulated based on Brillouin light-scattering (BLS) spectroscopy and a complete self-consistent model to obtain the time evolution of carrier density and temperature as well as lattice temperature. The results indicate that the trend of the lattice temperature is consistent with the experimental phenomena. Meanwhile, the electron-phonon coupling effect, in addition to the electron density traditionally considered, is an important factor affecting damage and is a major contributor to the anisotropy of the damage threshold.

First-principles study on the electronic structures and optical properties of Mg-doped KDP crystal

First-principles method was employed to study the defect formation energy, electronic structure, and optical properties of Potassium Dihydrogen Phosphate (KDP) crystals doped with Mg in both paraelectric phase (PE-KDP) and ferroelectric phase (FE-KDP). Additionally, we employed the HSE hybrid density functional to address the issue of “band gap” and utilized the finite size correction-finite volume (FNV) method to rectify defect formation energies. Due to hybridization of Mg-3s orbitals with O-2p orbitals, a defect energy level is created at the conduction band minimum (CBM), resulting in the band gap of Mg-doped KDP crystals being smaller than that of perfect crystals. Moreover, the incorporation of Mg leads to significant lattice distortions and alters bond lengths, particularly the O–Mg bonds, which are stretched by 0.65–0.77 Å. The optical spectra also have been obtained under the consideration of electron-phonon coupling. The absorption peak locates at 4.37 eV (284 nm) in PE-KDP. The absorption peak locates at 4.66 eV (266 nm) in FE-KDP. Moreover, the significant Stokes shifts (3.67 eV and 2.9 eV) observed in Mg-doped KDP crystals were attributed to lattice relaxation energy and distortions induced by the substitution. The calculated results indicate that the quality of the KDP crystals may be reduce by introducing Mg-impurities. The work provides valuable insights into the optical characteristics of Mg-doped KDP crystals and their potential applications in laser technology.