Crystal Length Research Articles

Picosecond synchronously pumped diamond Raman laser

With diamond crystals as Raman media, picosecond synchronously pumped solid-state Raman laser is theoretically studied in detail for the first time. High efficient working point and effective pulse compression working point are investigated. For both 532 nm and 1064 nm pumping, high Raman conversion efficiency can be achieved for negative cavity length detuning (∆x) and diamond crystal length of 5 mm. The higher efficiency can be obtained with longer Raman crystal, longer pumping pulse width and higher pumping power. For 532 nm pumping, effective pulse width compression can be realized for ∆x = 0 nearby and diamond crystal length of 10 mm. Shorter pulse width and higher peak power of 1st Stokes laser can be achieved with longer Raman crystal, shorter pumping pulse width and higher pumping power. The findings can contribute to the design and optimization of picosecond synchronously pumped diamond Raman lasers.

Efficient Broadband Frequency Conversion via Shortcuts to Adiabaticity

AbstractThe method of adiabatic frequency conversion, in analogy with a two‐level atomic system, has been put forward recently and verified experimentally to achieve robust frequency mixing processes such as sum and difference frequency generation. Here a comparative study of efficient frequency mixing using various techniques of shortcuts to adiabaticity such as counter‐diabatic driving and invariant‐based inverse engineering is presented. It is shown here that it is possible to perform sum frequency generation by properly designing the poling structure of a periodically poled crystal and the coupling between the input lights and the crystal. The required crystal length for frequency conversion significantly decreases beyond the adiabatic limit. This approach significantly improves the robustness of the process against the variation in temperature as well as the signal frequency. By introducing a single parameter control technique with constant coupling and combining with the inverse engineering, perturbation theory, and optimal control, it is shown that the phase mismatch can be further optimized with respect to the fluctuations of input wavelength and crystal temperature that results into a novel experimentally realizable mixing scheme.

Efficient ternary organic solar cells with BT-rhodanine-based nonfullerene acceptors in a PM6:Y6-BO blend

A series of benzothiadiazole (BT)–rhodanine-based nonfullerene acceptors (NFAs) were designed and synthesized. These BT–rhodanine-based NFAs were composed of BT as a central core with a 3-octylthienothiohene π-bridge and two different rhodanine end groups (BT-rho for octylrhodanine and BT-rhoCN for dicyano-octylrhodanine end groups). The highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels were −5.53/−3.78 eV for a BT-rho film and −5.63/−3.90 eV for a BT-rhoCN film. The strong electron-withdrawing dicyano-octylrhodanine end group of BT-rhoCN downshifted the HOMO and LUMO levels by ∼0.1 eV compared with those of BT-rho. The 10% BT-rho in a PM6:Y6-BO ternary organic solar cell exhibit a maximum power conversion efficiency (PCE) of 16.17% with a short-circuit current density ( J SC ) of 25.29 mA cm −2 , open-circuit voltage ( V OC ) of 0.84 V, and fill factor ( FF ) of 76.13%. The hole/electron mobilities of the PM6:Y6-BO, 10% BT-rho, and 10% BT-rhoCN ternary devices were 2.20 × 10 −4 /1.85 × 10 −4 cm 2 V −1 s −1 , 3.66 × 10 −4 /3.77 × 10 −4 cm 2 V −1 s −1 , and 1.34 × 10 −4 /0.94 × 10 −4 cm 2 V −1 s −1 , respectively. The crystal coherence lengths ( L C s) of the (010) peaks for the PM6:Y6-BO, 10% BT-rho, and 10% BT-rhoCN ternary films are 43.2, 60.8, and 33.7 Å, respectively. The superior PCE of the 10% BT-rho ternary devices compared with that of the PM6:Y6-BO binary device is attributed to the enhanced hole and electron mobilities and the high crystallinity of the blend films, which contribute to the enhancement of the J SC and PCE. • New BT-based acceptors, BT-rho and BT-rhoCN, were synthesized by inserting rhodanine terminal groups. • Rhodanine end groups of BT-rho lowered the LUMO level and thus increased the open-circuit voltage. • An enhanced PCE of 16.17% was achieved using BT-rho as a third component in a PM6:Y6-BO blend.

Variations in Microstructural and Physicochemical Properties of Soy Wax/Soybean Oil-Derived Oleogels Using Soy Lecithin.

Emerging natural-based polymers and materials progress and new technology innovations open the way for unique food products with high nutritional value development. In this regard, oleogel may be essential in replacing fatty acids from food products. In this study, we researched the effects of varied soy lecithin (SYL) concentrations on the various physicochemical characteristics of soy wax (SW)/refined soybean oil (RSO) oleogels. These oleogels had a soft texture. The microscopic analysis of the oleogels suggested that the thickness, length, and density of the wax crystals (needle-shaped) varied as the SYL content was changed. Colorimetric analysis indicated that the oleogels were slightly yellowish. FTIR spectrometry helped analyze the functional groups of the raw materials and the oleogels. All the functional groups present in the raw materials could be accounted for within the oleogels. The only exception is the hydrogen-bonding peak in SW, which was not seen in the FTIR spectrum of the oleogels. It was found that at a critical SYL content, the oleogel showed a stable and repeatable wax network structure. This can be described by the presence of the uniformly distributed fat crystal network in the sample. The DSC analysis revealed that the oleogel samples were thermo-reversible, with their melting and crystallization temperatures ~43 °C and ~22 °C, respectively. In gist, it can be concluded that the incorporation of SYL can impact the color, wax crystal network characteristics, thermal characteristics, and mechanical characteristics of the oleogels in a composition-dependent manner.

An Attempt to Relate Oleogel Properties to Wax Ester Chemical Structures.

Wax esters are considered to have a dominant contribution in the gelling properties of wax-based oleogels. To understand their gelling behavior, oleogels of seven different wax esters (total carbon number from 30 to 46; c = 10% [m/m]) in medium-chain triglycerides oil were characterized. Scanning electron microscopy revealed that wax esters crystallize in rhombic platelets with a thickness of 80 to 115 monomolecular layers. Bright field microscopy showed that the regularity and face length of the crystals increased with the total carbon number and molecular symmetry of the respective wax ester. Oscillatory rheology was used to characterize the gel rigidity (). Here, wax ester oleogels with smaller total carbon numbers yielded higher values than those of wax esters with higher total carbon numbers. The gel rigidity () inversely correlated with the crystal face length. Smaller and optically less well-defined platelets promoted higher gel rigidities. In the case of the microstructure of a specific oleogel composition being manipulated by a variation in the cooling rates (0.8; 5; 10 K/min), this relationship persisted. The information compiled in this manuscript further elucidates the crystallization behavior of wax esters in oleogels. This contributes to the understanding of the composition–structure–functionality relationship of wax-based oleogels supporting future food applications.

Detuning modulated composite segments for robust optical frequency conversion

The creation of efficient broadband frequency conversion devices while maintaining robustness to manufacturing and setup errors is crucial for accurate multiphoton spectroscopy, broadband imaging and the design of robust optical sources. Traditionally, nonlinear optical conversion processes are either efficient but narrowband or broadband but with low photon conversion yield. Several methods have been introduced in recent years to obtain both with great success, among them we can find adiabatic frequency conversion and Shaka–Pines composite segmented design. Here, we expand the composite design and introduce the detuning modulated composite segmented (DMCS) scheme in nonlinear optics, which offers a broadband, efficient and robust method for frequency conversion. We also present the constant-length DMCS scheme, which offers multiple efficient and robust wavelength regimes for broadband upconversion. We apply these schemes to a system of quasi-phase-matching crystal for the sum frequency generation process, and demonstrate the high robustness and bandwidth of the composite schemes. We show that these schemes are robust to temperature and crystal length variations and can have a superior conversion bandwidth under length and power constraints compared to other conversion schemes, such as periodically poled and adiabatic chirped crystals. We believe that the new family of DMCS schemes will have many uses in applications of frequency conversion, due to their robustness, low energy demand and compact size.

Optimization of the nonlinear crystal length for high-power single-frequency intracavity frequency-doubling lasers.

We report a method of optimizing the nonlinear crystal length of the intracavity frequency-doubling laser, which is achieved by maximizing the output power of the frequency-doubling laser in the case of ensuring the single longitudinal mode (SLM) operation of the laser. The optimal length of the nonlinear crystal for an SLM oscillation of the intracavity frequency-doubling laser is firstly theoretically predicted by comparing the losses introduced by the nonlinear crystal with different lengths with that of ensuring the SLM operation of the laser. Then three nonlinear LiB3O5 (LBO) crystals with the length of 18, 20, and 22 mm are adopted to be the frequency-doubling components in the experiment. By recording the output power and monitoring the longitudinal mode structure of the laser, it is found that the nonlinear LBO crystal with the length of 20 mm is the best candidate, since the output power is higher than that of the LBO crystal with the length of 18 mm, and the SLM operation of the laser is readily achieved compared to that of the LBO crystal with the length of 22 mm. The experimental results well agree with the theoretical predictions. The current method can pave a good way to attain a single-frequency continuous-wave intracavity frequency-doubling laser.

Role of Er on the densification, microstructure and mechanical properties of 7075 aluminium alloys manufactured by laser powder bed fusion

Fabricating crack-free 7075 aluminium alloy by laser powder bed fusion (LPBF) is currently a hot research topic. In this work, pre-alloyed 7075Al + Er powder was prepared, and crack-free samples were printed by LPBF by adjusting the process parameters. Furthermore, the influence of process parameters and the mechanism of crack inhibition by Er were discussed. Er can generate Al3Er coherent with the Al matrix, which has the grain refinement effect, shortens the length of columnar crystals from 106 μm to 84 μm and is conducive to the dispersion and further solidification of the liquid film in the paste solidification stage. Al3Er also reduces the texture strength and makes the thermal stress more uniform. The final measured tensile strength of the printed sample was 338 MPa, and the elongation was 15.9%, which was 32% and 74.7% higher than those of the 7075Al samples without Er addition, respectively. In this work, the effect of rare earth element Er on the improvement of the printability and crack suppression of 7075 aluminium alloy by laser powder bed fusion was discussed, which provides experimental support for crack-free additive manufacturing and application of high-strength aluminium alloys.

Optimizing the Intercrystallite Connection of a Donor–Acceptor Conjugated Semiconductor Polymer by Controlling the Crystallization Rate via Temperature

Back Cover: In article number 2200084 by Hua Yang, Yu Chen, Yanchun Han and co-workers, the tie-chain connection behavior of conjugated polymer thin film is optimized by decreasing the crystal region length (lc) and increasing the crystallization rate. The film prepared at 55 °C exhibits a smaller crystal region length (lc, 7.6 nm), the highest tie-chains content, and the best device mobility.

Synthesis and characterization of 1,4-di(1H-imidazol-1-yl) butane dihydrate and 1,4-di(1H-2-methylimidazol-1-yl) butane tetrahydrate: A study of the methyl group effect on spectroscopic data, thermal properties, and the crystal structures

Two bis(imidazole) derivatives, 1,4-di(1H-imidazol-1-yl) butane dihydrate (DImB·2H2O) and 1,4-di(1H-2-methylimidazol-1-yl) butane tetrahydrate (DMImB·4H2O were synthesized. The crystallization was performed from an aqueous ethanol by slow evaporation technique. X-ray crystallography was used to confirm the molecular structures of both crystals. The results from crystal structure analysis displayed that DImB·2H2O was crystallized in the orthorhombic crystal system and Pbca space group with a = 14.7805(4) Å, b = 5.22600(10) Å, and c = 15.6110(4) Å. The molecule lies in the center of inversion, making the asymmetric unit consist of half of the parent molecule with one unit of the water molecule, whereas DMImB·4H2O displayed the triclinic crystal system and R-3 space group with a = 21.526(3) Å, b = 21.526(3) Å, and c = 9.3333(12) Å. The molecule lies on a center of inversion, making the asymmetric molecules consist of half of the parent molecule with two units of the water molecules. The effect of replacing hydrogen atoms at C2 of two imidazole rings with the methyl groups on spectroscopic properties was investigated using FTIR, MS, 1H, and 13C NMR. The infrared spectrum demonstrated the presence of water molecules in DMImB·4H2O, which showed a more intense O‒H group peak than DImB·2H2O. The effect of methyl groups was studied on the chemical shifts, multiplicity, and coupling constants of hydrogen atoms, and carbon chemical shifts of imidazole rings. Mass spectra of both compounds showed [M+Na]+ and [2M+Na]+ in positive ion mode (ESI+). In addition, the thermal phase transitions and thermal stability of the bis(imidazole) derivatives were studied using the DSC and TGA/DTG. The crystalline structures of DImB and DMImB recorded and the methyl effect was investigated on the size of molecules, arrangement of molecules in the crystal lattice, lattice planes, solvent void, length, angle, and torsion.

Maximum intensity determination of beam waist in BBO optical nonlinear crystal using single harmonic generation

Nonlinear optics is a branch of optics that explains the nonlinear response of atoms and molecules to a field of light radiation. There is a difficulty in cutting crystals in shapes commensurate with their optical properties, and thus it was significant to determine the descriptive shape of crystal properties based on its optic properties to be ideal in use. The problem of determining the length of the crystal to give the best output power is still under study and research and is one of the most important topics. In our research, a computational method based on mathematical relationships was used to estimate the length of the BBO crystal of I-type, which gives the best output power, by manipulating the location of the optical light scattering to be in the middle of the crystal. It was found that the best length of a crystal with a width of 3mm and a height of 3mm is 7mm. the comparison of these results with the previous literatures gave a great match, which confirms the correctness of the computations and the reliability of used method.

Investigation of Electronic Signal Processing Chains for a Prototype TOF-PET System With 100-ps Coincidence Time Resolution.

We have evaluated CTR performance of four different mixed-signal front-end electronic readout configurations with the goal to achieve 100 picoseconds (ps) coincidence time resolution (CTR). The proposed TOF-PET detector elements are based on two 3 × 3 × 10 mm3 "fast LGSO" crystal segments, side-coupled to linear arrays of 3 × 3 mm2 silicon photomultipliers (SiPMs), to form a total crystal length of 20 mm. We studied multiple configurations and components for the front-end readout: 1) high speed radio frequency (RF) amplifiers; 2) an ASIC-based discriminator; 3) combination of RF amplifier, balun transformer, and discriminator ASIC; and 4) combination of balun transformer, and discriminator ASIC. Using two 3 × 3 × 10 mm3 fast LGSO crystals side coupled to a linear array of three SiPMs, coincidence data were experimentally acquired for each readout configuration in combination with a low jitter field programmable gate array (FPGA)-based time to digital converter (TDC). After evaluating timing performance of the three readout schemes, the best CTR value of 99.4 ± 1.9 ps FWHM was achieved for configuration (3), which is more than 20 ps better than the results achieved using configurations (1) and (2).

High Pulse Energy, Narrow Linewidth 6.45 μm from an Optical Parametric Oscillator in BaGa4Se7 Crystal

This paper presents a high pulse energy, narrow linewidth, mid-infrared (MIR) laser at 6.45 μm, based on a BaGa4Se7 (BGSe) crystal optical parametric oscillator (OPO) pumped by 1.064 μm laser. The maximum pulse energy at 6.45 μm was up to 1.23 mJ, with a pulse width of 24.3 ns and repetition rate of 10 Hz, corresponding to an optical–optical conversion efficiency of 2.1%, from pump light 1.064 μm to idler light 6.45 μm. The idler light linewidth was about 6.8 nm. Meanwhile, we accurately calculated the OPO phase-matching condition at BGSe crystal pumped by 1.064 μm laser, and a numerical simulation system was performed to analyze the input–output characteristics at 6.45 μm, as well as the effect of crystal length on the conversion efficiency. Good agreement was found between measurement and simulation. To the best of our knowledge, this is the highest pulse energy at 6.45 μm, with the narrowest linewidth for any all-solid-state MIR ns laser in BGSe-OPO pumped by simple 1.064 μm oscillator. This simple and compact 6.45 μm OPO system, with high pulse energy and narrow linewidth, can meet the requirements for tissue cutting and improve tissue ablation accuracy.

Multipanel Limited Angle PET System With 50 ps FWHM Coincidence Time Resolution: A Simulation Study

In this simulation study, we evaluate the performance of a limited angular coverage PET system consisting of two/four fast-timing 50 ps FWHM CTR flat-panel detectors made of 5–20 mm long pixelated lutetium oxyorthosilicate crystals. We studied image quality and count rates following the National Electrical Manufacturers Association standard, spatial resolution by imaging a Derenzo phantom and a hot rod, and investigated the sensitivity of different scanner designs. We demonstrated the possible use of such a scanner by imaging a human head and a torso of the extended cardiac-torso (XCAT) digital phantom. All the designs were compared to the reference scanner, based on Siemens Biograph Vision PET/CT scanner geometry. We show that good coincidence timing resolution (CTR) can compensate for lower detection efficiency or smaller angular coverage. Good image quality can be obtained with a simple limited-angle PET system without distortions or artefacts. Substantial degradation of the spatial resolution with increased crystal length is observed in the two-panel design due to the parallax error, but not in the four-panel design. The four-panel design simulated with a CTR of 50 ps FWHM is comparable to that of the current state-of-the-art clinical PET/CT scanner. Similar fast-timing limited-angle planar detectors could enable much less expensive total-body or single organ (dynamically selectable) imaging devices.

Preparation aragonite whisker-rich materials by wet carbonation of cement: Towards yielding micro-fiber reinforced cement and sequestrating CO2

In this study, an innovative wet carbonation process was developed to prepare aragonite whisker-rich materials (AWM) from cement and simulated flue gas, which subsequently served as micro-fiber additions to cement. The parameters including temperature, duration and MgCl2 concentration governing the aragonite formation were investigated, and the formation mechanism was explored. The results showed that needle-like aragonite whisker with a single crystal length of 10–30 μm and diameter of 0.5–2 μm could be synthesized rapidly when the cement suspension containing 0.05 M/L MgCl2 was carbonated at 80 °C. The formation of aragonite was favored in a suspension with a high concentration of Ca2+ and a minimum Mg2+/Ca2+ molar ratio >0.12. Additionally, amorphous phases including alumina-silica gel and silica gel were also detected. By mixing the AWM with cement, a new type of micro-fiber reinforced cement was developed, which showed significant mechanical performance improvement and embodied CO2 content (25.3 %).

Synthesis, Spectroscopic, Crystal Structure, DFT, Hirshfeld Surface and Molecular Docking Analysis of Hexahydroquinoline Derivative (HQ)

The synthesis of a HQ derivative using a one-pot multicomponent synthesis is reported. Single crystal X-Ray diffraction at 293 K was used to characterize the material, which was then investigated theoretically using the DFT method. The 3 D Hirshfeld surface and 2 D fingerprint plots were created and linked with the XRD results to elucidate intermolecular interactions in the crystal lattice. In addition, FT-IR, UV-Vis, 1H, and 13 C were used to support the synthesis. Theoretical data calculated via DFT/6-311++G(d,p) level, matched to experimental single crystal X-ray diffraction bond lengths and bond angle parameters, NMR and FT-IR spectra, coincides with experimental data. The time dependent (TD-DFT) results correlates with the experimental electronic absorption measurements. Mulliken population analysis, Molecular Electrostatic Potential analysis (MEP), and Electron Localization Function (ELF) study were also performed. TD-DFT and HOMO/LUMO computations were used to examine the electron transport. Molecular docking using 7 protein receptors and drug Likeness were used to find the best ligand-protein interactions.

Effect of N and Al Doping on 3C-SiC Stacking Faults

This study offers a comprehensive examination of the behavior of 3C-SiC crystals grown on 4° off-axis (100) Si substrates with different off-axis angles along <110> and <100> for N and Al doping, respectively. The investigation takes advantage of molten KOH etching to conduct an in-depth investigation of the average density and size of the SFs inside the crystal for both n- and p-type doped 3C-SiC epitaxial layers. Moreover, 3C-SiC grown on a <100> off-cut substrate was revealed to have a greater concentration of SFs due to the absence of self-annihilation along the plane (-1-10). Considering two different doping ranges suitable for IGBTs and MOSFETs development, the impact of doping and off-angle on the crystal quality, concentration, and length distribution of SFs was then investigated in order to quantify the influence of N and Al incorporation on the structural and optical characteristics of the semiconductor. It turned out that under heavy nitrogen doping (~1019 cm-3), when the dopant concentration grew, the average length of the stacking faults (SFs) expanded while their density dropped.

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10

Ultrasound-induced protein restructuring and ordered aggregation to form amyloid crystals

Amyloid crystals, a form of ordered protein aggregates documented relatively recently, have not been studied as extensively as amyloid fibres. This study investigates the formation of amyloid crystals with low frequency ultrasound (20 kHz) using β-lactoglobulin, as a model protein for amyloid synthesis. Acoustic cavitation generates localised zones of intense shear, with extreme heat and pressure that could potentially drive the formation of amyloid structures at ambient bulk fluid temperatures (20 ± 1 °C). Thioflavin T fluorescence and electron microscopy showed that low-frequency ultrasound at 20 W/cm3 input power induced β-stacking to produce amyloid crystals in the mesoscopic size range, with a mean length of approximately 22 µm. FTIR spectroscopy indicated a shift towards increased intermolecular antiparallel β-sheet content. An increase in sonication time (0–60 min) and input power (4–24 W/cm3) increased the mean crystal length, but this increase was not linearly proportional to sonication time and input power due to the delayed onset of crystal growth. We propose that acoustic cavitation causes protein unfolding and aggregation and imparts energy to aggregates to cross the torsion barrier, to achieve their lowest energy state as amyloid crystals. The study contributes to a further understanding of protein chemistry relating to the energy landscape of folding and aggregation. Ultrasound presents opportunities for practical applications of amyloid structures, presenting a more adaptable and scalable approach for synthesis.Graphical abstract

Highly efficient generation of narrowband terahertz radiation driven by a two-spectral-line laser in PPLN.

We demonstrate record ∼0.9% efficiencies for optical conversion to narrowband (<1% relative bandwidth) terahertz (THz) radiation by strongly cascaded difference frequency generation. These results are achieved using a novel, to the best of our knowledge, laser source, customized for high efficiencies, with two narrow spectral lines of variable separation and pulse duration (≥250 ps). THz radiation generation in 5% MgO-doped periodically poled lithium niobate (PPLN) crystals of varying poling period was explored at cryogenic and room temperature operation as well as with different crystal lengths. This work addresses an increasing demand for high-field THz radiation pulses which has, up to now, been largely limited by low optical-to-THz radiation conversion efficiencies.