Damage Threshold Research Articles

Single crystal of barium bis para-nitrophenolate para-nitrophenol tetrahydrate for NLO applications: crystal growth and DFT analysis

Abstract Single crystals of barium bis para-Nitrophenolate para-Nitrophenol tetrahydrate (BBPNT) were grown via the slow evaporation technique. The crystal dimensions were measured to be 15 mm × 10 mm × 6 mm. The BBPNT crystal was analyzed using X-ray diffraction, FTIR spectrum, UV–vis spectrum, dielectric studies, thermo-gravimetric (TG) differential thermal analyses (DTA), Vickers microhardness test, second-harmonic generation efficiency, Z-scan technique, PL spectra, and laser damage threshold studies. These findings were previously published in our paper. In the current situation, the theoretical methods include analyzing several aspects, such as the molecular structure determined using X-ray experimentation at its lowest energy state. This analysis is then contrasted by means of density functional theory (DFT) with a suitable set of basic functions. The first-order hyperpolarizability may also be determined via the use of Density Functional Theory (DFT) methods. The molecule’s stability, resulting from hyper conjugative interactions, was examined using the natural bond orbital approach to analyses its nonlinear optical activity and charge delocalization. The magnitude of the HOMO–LUMO energy gap indicates the potential for charge transfer inside the molecule. The investigation of donor-acceptor interactions was conducted using NBO analysis based on optimized ground state geometries.

Numerical Modeling of Mid-IR Lasers Based on Tb-Doped Chalcogenide Multicore Fibers

Mid-IR fiber lasers operating at wavelengths near 5 μm are of great interest for many fundamental and industrial applications, but only a few experimental samples based on active chalcogenide fibers have been demonstrated so far. One of the limitations of the power of such lasers may be a fairly low fiber damage threshold. To solve this problem, we developed and numerically investigated in detail a mid-IR fiber laser at 5.3 µm with multi-W output power pumped into the cladding at a wavelength of 2 µm. We proposed using a Tb-doped chalcogenide multicore fiber with 25 single-mode cores arranged in a 5 × 5 square lattice as an active medium. The proposed laser design surpasses the power limit of single-core chalcogenide fibers. When simulating lasers, we specified realistic parameters of Tb-doped chalcogenide glass based on published experimental data. We performed a comprehensive theoretical analysis, studied the influence of various factors on the characteristics of generation, and found optimal system parameters and expected generation parameters.

Evaluation of Damage Stress Thresholds and Mechanical Properties of Granite: New Insights from Digital Image Correlation and GB-FDEM

We employed a novel combination of digital image correlation (DIC) and grain-based hybrid finite–discrete element method (GB-FDEM) to improve the comprehension of the relationships between microstructural features and the mechanical properties of granitic rocks. DIC and numerical results showed that macrocracks initiated and propagated along grain boundaries among different minerals driven by the high stiffness contrast between the compliant biotite and the stiffer feldspar/quartz grains. Surface deformation analyses revealed that tensile-dominated macrocracks open at monotonically increased rates before the crack damage threshold, and the opening accelerated afterwards with the increased shear component. The onset of the acceleration of the opening rate of macrocracks can be used to infer the crack damage threshold. Both strain and acoustic emission were used to infer damage stress thresholds in the synthetic numerical samples. Numerical results showed that the damage stress thresholds and uniaxial compressive strength decrease with increasing grain size following log-linear relations. Coarse-grained samples tend to fail by axial splitting, while fine-grained samples fail by shear zone formation. Biotite and quartz contents significantly affect mechanical properties, while quartz to feldspar ratio is positively related to the mechanical properties. Our study demonstrates the capacities of DIC and GB-FDEM in inferring damage conditions in granitic rocks and clarifies the microstructural control of the macroscopic mechanical behaviors. Our results also provide a comprehensive understanding of the systematics of strain localization, crack development, and acoustic emission during the rock progressive failure process.

Design optimization of an axial turbine and study on its fish passing characteristics

In this paper, a new type of helical blade is introduced, which is designed to minimize the damage of hydraulic turbine to fish. The experiments test the damage for fish under different pressure and pressure gradients. Also, the parameters of the helical blade turbine are optimized based on the damage thresholds. The consequent axial flow turbine features double-blades with a pitch of 2600 mm and a blade envelope angle of 540°. To assess the turbine's impact on fish, an overlapping mesh method is used to analyze the degree of damage to the fish during operation. The findings show that, compared to traditional designs, the application of helical blade turbine significantly reduced the exposure and duration of negative pressure, high pressure gradient, and high shear force.

Preclinical assessment of a noncooled MR thermometry-based neurosurgical laser therapy system.

MRI-guided laser interstitial thermal therapy (MRgLITT) has recently gained interest as an ablative stereotactic procedure for intractable epilepsy, movement disorders, and brain tumors. Conventionally, a LITT system consists of a laser generator and cooled laser applicator, which is a fiber optic core surrounded by a sheath through which cooled fluid is pumped. However, this footprint can make the system bulky and nonmobile, limit the maximum depth of targeting, and increase the chances of breakdown. Herein, the authors conduct a preclinical assessment of a noncooled MRgLITT system in a porcine model. Three-tesla MRI was used to guide the in vivo placement of noncooled laser applicators in the porcine brain. The study consisted of a survival arm and terminal arm. The laser was activated at a power of 4-7 W for ≤ 180 seconds. Temperature changes were monitored using the MR thermometry software ThermoGuide in the survival arm (n = 5) or both ThermoGuide software and adjacently inserted thermal probes in the terminal arm (n = 3). Thermal damage was determined by the software using the temperature-time relationship of cumulative equivalent minutes at 43°C (CEM43). Temperatures calculated by the software were compared with those recorded by the temperature probes. The dimensions of thermal damage thresholds (TDTs; 2-9, 10-59, 60-239, ≥ 240 CEM43 isolines) given by MR thermometry were compared with the dimensions of irreversible damage on histopathological analysis. There was a strong correlation between temperature recordings by ThermoGuide and those by thermal probes at both 4 mm (r = 0.96) and 8 mm (r = 0.80), with a mean absolute error of 0.76°C ± 2.13°C and 0.17°C ± 1.65°C at 4 and 8 mm, respectively. The area of 2-9 CEM43 was larger than the area of irreversible damage seen on histopathological analysis. The dimensions of the 10 and 60 CEM43 correlated well with dimensions of the lesion on histopathological analysis. A well-defined border (≤ 1 mm) was observed between the area of irreversible damage and healthy brain tissue. This preclinical assessment showed that the noncooled LITT system was able to precisely reach the target and create well-defined lesions within a margin of safety, without any adverse effects. MR thermometry software provided an accurate near-real-time temperature of the brain tissue, and dimensions of the lesion as visualized by the software correlated well with histopathological findings. Further studies to test the system's efficacy and safety in human subjects are in progress.

CONTEXTUALIZATION OF HISTORY AND DEVELOPMENT

The field of optical materials research stands at a pivotal juncture, driven by the relentless pursuit of advancements in laser technology. This study delves into the development and characterization of novel optical materials designed to enhance the performance and reliability of laser systems. Through a comprehensive investigation combining theoretical modeling, material synthesis, and empirical analysis, we identify key material properties that significantly influence laser efficiency and stability. Our research focuses on the exploration of new dopants, host materials, and fabrication techniques to achieve optimal thermal management, higher damage thresholds, and improved lasing efficiencies.

Few-mode metal-free perovskite optical fiber with second-order optical nonlinearity

Semiconductor core optical fibers are highly desirable for fiber-based photonic and optoelectronic applications as they can combine strong optical nonlinearities, tight light confinement, wide transmission bands, and electronic functionality within a single platform. Perovskites have emerged as particularly exciting materials for semiconductor photonics as they have strong optical nonlinearities and tunable optoelectronic bandgaps. However, lead-based perovskites contain toxic elements and are, therefore, not environmentally friendly. Furthermore, in fiber form, their core-size is prohibitively large, making them unsuitable for nonlinear optics and applications that require single-mode guidance, such as telecommunications. Here, we report a metal-free perovskite core optical fiber where lead has been substituted for an ammonium cation in the perovskite structure. The core material has a wide bandgap greater than 5 eV, a high laser damage threshold, and a core diameter that can be produced as small as 5 µm. At this core size, the fiber supports just six modes, and the fundamental mode can readily be excited and isolated. Moreover, the metal-free perovskite has a second-order susceptibility that is absent in the archetypal lead-based perovskites and many other semiconductor core materials, such as silicon and germanium. The second-order susceptibility is important for many nonlinear optics applications, such as second-harmonic generation and quantum optics.

Acoustic ground effects simulations from asteroid disruption via the “Pulverize It” method

Our simulations show that PI (“Pulverize It”), a NASA Phase II NIAC study, is an effective multi-modal approach for planetary defense that can operate in extremely short interdiction modes (with intercepts as short as hours prior to atmospheric entry) as well as long interdiction time scales with months to years of warning. The basic process is complete disruption of the threat via fragmentation. In long warning time cases, the fragment cloud spreads enough to miss Earth, resulting in no ground effects. In cases where the warning time is short, the fragments (typically <10 m in diameter) will enter Earth’s atmosphere where their energy is dissipated in a series of ground-level optical pulses and de-correlated shock waves, mitigating any significant damage. We investigate the acoustic ground effects through a set of simulation codes that model the interaction of asteroid fragments with the Earth’s atmosphere following threat interception. Even in the short warning time cases where the fragments enter the atmosphere, our simulations show that threats mitigated by the PI method produce vastly less damage on the ground when compared to the same unfragmented case, yielding shock wave over-pressures under 3 kPa. Our simulations support the proposition that threats sized 20 m—1000 m in diameter can be effectively mitigated through fragmentation, resulting in acoustic ground effects that are below estimated damage thresholds and yield short- and long-term non-lethal effects.

TECHNOLOGICAL ADVANCEMENTS IN SOLID-STATE LASERS AND FIBER LASERS

In this article through a comprehensive investigation combining theoretical modeling, material synthesis, and empirical analysis, we identify key material properties that significantly influence laser efficiency and stability. Our research focuses on the exploration of new dopants, host materials, and fabrication techniques to achieve optimal thermal management, higher damage thresholds, and improved lasing efficiencies.

Super-resolution reconstruction for subsurface defects of optical elements based on CdSe/ZnS quantum dots fluorescence dichroism

The subsurface defects (SSD) of optical elements have a significant impact on the service life and laser damage threshold of the inertial confinement nuclear fusion optical system. Due to the optical diffraction limit, fluorescence microscopy has limited image resolution for detecting SSD in optical elements, making it challenging to meet the requirements for precision detection. A super-resolution method is proposed in this paper for detecting SSD in optical elements based on the fluorescence polarization characteristics of CdSe/ZnS quantum dots fluorescence dichroism. By enhancing the imaging sparsity of adjacent fluorophores through a polarization modulated excitation laser and utilizing the fluorescence polarization modulation algorithm, the resolution is achieved beyond the optical diffraction limit. The results demonstrate that the proposed method in this paper can obtain super-resolution images of SSD in optical elements with at least a two-fold increase in lateral resolution. This approach effectively improves detection accuracy for SSD and holds significant guiding significance. In addition, it also has application value for assessing the quality of high-precision optical elements.

Micro-constructive Damage Model of Dry-Wet Cyclic Red Clay Based on Weibull Distribution

Abstract To address the strength damage of red clay under dry-wet cycles, systematic conventional triaxial tests under specific circumferential pressure and scanning electron microscope observation were carried out to describe the damage evolution of soil units under load conditions of dry-wet cycle red clay microunits based on the Weibull distribution. Damage variable expressions obeying the Weibull distribution were established and the micro-parameter pore area ratio and the macro-parameter dry-wet cycle number were introduced. The cross-scale characterization of macroscopic and microscopic parameters was realized by combining the damage mechanics equation of red clay under loading. The microscopic damage intrinsic model of red clay considering the number of dry-wet cycles was constructed. The model was verified to be reasonable and effective based on triaxial tests, in which the calculation errors of the secant modulus damage threshold, probability density function shape parameter, and dry-wet cycle red clay damage stress were within 10 %, 5 %, and 5 %, respectively.

Tunable and stable micro-ring resonator based on thin-film lithium tantalate

As ferroelectric materials, lithium tantalate and lithium niobate share similar material characteristics, such as a high Pockels effect and nonlinear optical coefficients. When compared to lithium niobate, lithium tantalate offers a higher optical damage threshold, a broader transparent window, and lower birefringence, making it a promising candidate for high-performance electro-optical photonic integrated devices. In this study, we design and successfully fabricate micro-ring resonators on an acoustic-grade lithium-tantalate-on-insulator wafer, demonstrating their tunability and dynamic modulation capabilities. Experimental results indicate that the achieved thin-film lithium tantalate based micro-ring resonator exhibits an intrinsic Q-factor of 8.4 × 105, corresponding to a waveguide propagation loss of 0.47 dB/cm and a tuning efficiency of 1.94 pm/V. More importantly, as compared to those based on thin-film lithium niobate, a much weaker photorefractive effect and drift phenomenon around the 1550 nm wavelength under a direct-current drive are observed in the present fabricated thin-film lithium tantalate micro-rings with a silicon oxide over-cladding and a tuning electrode on top.

Understanding the Electron Beam Resilience of Two-Dimensional Conjugated Metal-Organic Frameworks.

Knowledge of the atomic structure of layer-stacked two-dimensional conjugated metal-organic frameworks (2D c-MOFs) is an essential prerequisite for establishing their structure-property correlation. For this, atomic resolution imaging is often the method of choice. In this paper, we gain a better understanding of the main properties contributing to the electron beam resilience and the achievable resolution in the high-resolution TEM images of 2D c-MOFs, which include chemical composition, density, and conductivity of the c-MOF structures. As a result, sub-angstrom resolution of 0.95 Å has been achieved for the most stable 2D c-MOF of the considered structures, Cu3(BHT) (BHT = benzenehexathiol), at an accelerating voltage of 80 kV in a spherical and chromatic aberration-corrected TEM. Complex damage mechanisms induced in Cu3(BHT) by the elastic interactions with the e-beam have been explained using detailed ab initio molecular dynamics calculations. Experimental and calculated knock-on damage thresholds are in good agreement.

Effectiveness of environmental regulations: firm’s decisions and welfare implications

In this paper, we compare four policy instruments–tax, subsidy, binding emissions and cap-and-trade, to determine which policy is the most effective and whether they are equivalent. We also examine if a firm’s policy preference differs from that of a policymaker. Our motivation stems from the global use of a wide array of pollution instruments. Using a game theoretic approach, we analyze how carbon abatement, production quantity, profitability and welfare vary between different policy tools. We find that the tax policy is equivalent to the binding emission standards while welfare comparison shows that the highest welfare is attributed to either the tax or subsidy policy depending on the levels of environmental damage. We find that both the policymaker and the firm prefer a subsidy policy under lower thresholds of environmental damage. Exploring hybrid policies, we find that a multi-part tariff contract jointly implements the socially optimal outcomes and leads to a win-win situation for both the firm and the policymaker. Our findings offer guidance for policymakers and managers to implement appropriate policies based on the degree of environmental damage and to consider using hybrid policies that achieve higher pollution abatement and improved welfare.

Ecological pollution features and health risk exposure to heavy metals via street dust and topsoil from Nkpor and Onitsha in Anambra, Nigeria.

The manuscript presents the investigation results on the pollution and risk of metal mines, and it is considered an important report on environmental pollution near mines in Nigeria, with archival value. The research involved soil sampling and heavy metal analysis for about 12 months in three metal mines. Based on these results, the paper provides information on pollution levels and hazards using well-known methods like pollution and ecological risk indexes. The increasing population in urban communities attracted by various industrial, economic and social activities causes contamination of atmospheric environment that can affect human health. We investigated heavy metal distributions, correlation coefficient among elements, ecological indices and probable health risk assessment in street dust and topsoil from Nkpor and Onitsha urban suburb, Nigeria. The mean concentration of heavy metals in car dust from Onitsha and Nkpor suburb follows thus: Fe > Mn > Cu > As > Pb > Ni > Cr. The decreasing trend of heavy metal in rooftop dust from both area: Fe > Mn > Cu > Pb > As > Ni > Cr whereas metal contents in topsoil were: Fe > Mn > Cu > Pb > Ni > Cr > As for both areas. The degree of pollution indices was characterized by contamination factor (CF), geo-accumulation factor (I-geo), pollution load index (PLI), Nemerow (PN), ecological and potential ecological risk index (ER and PERI) which indicated low pollution in the urban street environment. The results of Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that the estimated heavy metals displayed sources from atmospheric deposition, natural origin and anthropogenic sources. Risk assessment revealed that ingestion of dust and soil was the significant route for heavy metals exposure to the populace followed by inhalation, then dermal contact. Considering all factors, non-cancer risk was more prominent in children than adults and no significant health hazard could be attributed to both aged groups as of the period of study except for As and Ni that needs constant monitoring to avoid exceeding organ damaging threshold limit of 1 × 10-4.

Nanosecond laser damage of 532 nm thin film polarizers evaluated by different testing protocols

Different laser damage testing protocols, including 1-on-1, S-on-1, and Raster Scan, were conducted on 532 nm polarizers to evaluate the damage resistance and mechanisms. A comparison of the laser-induced damage thresholds (LIDTs) revealed different damage characteristics and major contributions to film failure for different polarizations. For P polarization, the LIDTs for the three test protocols were nearly the same because of the stabilization of two typical damage morphologies of flat-bottomed pits and mussel damage pits. For S polarization, the LIDTs for multiple pulses were lowest, where absorptive defect-induced damage was revealed. The damage characteristics of 532 nm polarizers and 1064 nm polarizers have been also compared. The mussel damage pits, which are similar to the typical damage morphologies of ultraviolet (UV) laser damage to fused silica, were observed for the first time in coatings of 532 nm polarizers. This suggests that, the polishing-induced subsurface damage of fused silica substrates may tend to be excited by a short-wavelength laser rather than the fundamental wavelength.

Growth and physiochemical properties of semi organic ammonium pentaborate dihydrate single crystal

Abstract The slow evaporation technique was used to produce nonlinear optical ammonium pentaborate dihydrate (APBDH) single crystals. The crystal lattice parameters and structure of APBDH crystal was determined by single crystal X-ray diffraction (S-XRD) technique with the triclinic space group. The optical band gap of the grown crystal was determined using UV–Vis spectrophotometer. There is no absorption peak was observed in the entire visible region of the spectrum. The functional groups of the APBDH crystal were identified through Fourier transforms infrared (FTIR) and Fourier transform Raman (FR-Raman) analyses. The thermal decomposition and thermal stability of the grown crystal was measured using TG-DTA analyses. The laser damage threshold (LDT) analysis was used to know the ability to withstand the influence of laser on the grown crystal. Photoconductivity of the grown crystal was studied and its photocurrent and dark current behavior was examined. The surface morphology of the APBDH crystal was evaluated using HR-SEM analysis. The APBDH crystal was exhibited second harmonic generation behavior and its efficiency was calculated with different particle sizes.

Experimental and theoretical interpretations of structural, optical, mechanical and thermal properties of 2-aminopyridinium phthalate single crystals

Nonlinear optical good quality single crystals of 2-aminopyridinium phthalate single crystals are synthesized by solution growth technique. Structural parameters are elucidated by Single Crystal X-ray diffraction method which reveals that the material crystallizes in non-centrosymmetric crystalline framework. Vibrational assignments are interpreted by Fourier Transform Infrared spectral analysis. The thermal, mechanical and laser stability are explored by TG/DTA, microhardness and Laser Damage threshold analysis. The material has good emission nature in the violet emission region. The linear optical properties are elucidated with the help of UV–visible spectral analysis. The intermolecular charge transfer interactions are analyzed by HOMO-LUMO and MESP maps by using Gaussian ’09 software program. The second harmonic generation efficiency of the synthesized material are predicted by Kurtz Perry powder technique.

The Influence of B4C Film Density on Damage Threshold Based on Monte Carlo Method for X-ray Mirror.

The uniformity and consistency of X-ray mirror film materials prepared by experimental methods are difficult to guarantee completely. These factors directly affect the service life of free electron laser devices in addition to its own optical properties. Therefore, the quality of the film material, especially the density, has a critical effect on its application. Boron carbide film and monocrystalline silicon substrate were suitable examples to explore their influence of density on the damage threshold based on Monte Carlo and heat-conduction methods. Through simulation results, it was found that the change in film density could affect the energy deposition depth and damage threshold. When the film density was 2.48 g/cm3, it had relatively high damage threshold in all energy ranges. And then the specific incident parameter for practical application was investigated. It was found that the damage mechanism of the B4C/Si was the melting of the interface. And the damage threshold was also higher with the film density of 2.48 g/cm3. Therefore, it was recommended to maintain the density at this value as far as possible when preparing the film, and to ensure the uniformity and consistency of the film material.

Improving fourth harmonic generation performance by elevating the operation temperature of ADP crystal.

In current inertial confinement fusion (ICF) facilities, potassium dihydrogen phosphate (KH2PO4, KDP) type crystals are the only nonlinear optical (NLO) materials that can satisfy the aperture requirement of the ICF laser driver. Ammonium dihydrogen phosphate (NH4H2PO4, ADP) crystal is a typical isomer of KDP crystal, with a large nonlinear optical coefficient, high ultraviolet transmittance, and large growth sizes, which is an important deep ultraviolet (UV) NLO material. In this paper, we investigated the effect of ADP temperature on its fourth-harmonic-generation (FHG) performance. When the temperature of the ADP crystal was elevated to 48.9 °C, the 90° phase-matched FHG of the 1064 nm laser was realized. Compared with the 79° phase-matched FHG at room temperature (23.0 °C), the output energy at 266 nm, conversion efficiency, angular acceptance, and laser-induced damage threshold (LIDT) increased 113%, 71%, 623%, 19.6%, respectively. It shows that elevating ADP temperature is an efficient method to improve its deep UV frequency conversion properties, which may also be available to other NLO crystals. This discovery provides a very valuable technology for the future development of UV, deep UV lasers in ICF facilities.