Laser Applications Research Articles

Evaluation of the effect of adjunctive diode laser application on peri-implant crevicular fluid biomarker levels: a randomized controlled trial

ObjectivesTo assess both the clinical and immunological effectiveness of diode laser therapy when used as an adjunct to non-surgical mechanical therapy in managing peri-implantitis.Materials and methodsA cohort of 27 participants, comprising 21 females and 6 males, agreed to take part in this investigation. 37 dental implants with peri-implantitis diagnosis were randomly allocated to either the laser group (n = 19) or the control group (n = 18). Evaluation of peri-implant clinical parameters and collection peri-implant crevicular fluid (PICF) samples occurred at baseline, as well as at 3 and 6-month follow-up intervals. The level of various biomarkers (TWEAK, IL-1β, sclerostin, IL-17, RANKL, OPG and IL-10) within the PICF were quantified using enzyme-linked immunosorbent assay.ResultsSignificant time-dependent decreases in clinical and biochemical parameters were detected in both groups compared to the baseline. There were marked differences between the groups in terms of periodontal parameters, except probing depth, and IL-1β, IL-17, sclerostin levels in PICF at 3rd month follow-up. However, no statistically significant difference was detected at 6th month.ConclusionsDiode laser seems to be a reliable tool as an adjunct for supporting the nonsurgical mechanical treatment during the early stages of peri-implantitis. Furthermore, the findings suggest that IL-17, sclerostin and IL-1β may serve as promising biomarkers for assessing efficacy of peri-implantitis treatment.Clinical relevanceBased on these outcomes, clinicians may consider the application of adjunctive use of diode laser to non-surgical peri-implantitis treatment to achieve better clinical and immunological improvements than nonsurgical peri-implantitis therapy alone in just early healing period. However, it should be noted that there was no difference between the two methods in the long term.

2.7μm luminescence and structural properties of Er3+-doped fluorotellurate glass

In this paper, the thermal properties and internal structures of fluorotellurate glasses with different concentrations of TeO2 were studied. Glass samples with a concentration of 30mol% TeO2 were doped with different concentrations of Er3+ (1,2, 3,3.5,4,4.5,5mol%) and their luminescence characteristics were analyzed. The fluorotellurate glass possess high infrared transmittance (93 %), thermal stability (ΔT>110 °C), and low phonon energy (821 cm−1). Er3+ doped fluorotellurate glass exhibits high fluorescence lifetime of 4I11/2 level (1.59 ms), large emission cross-section (5.98 × 10−21cm2), and achieves a quantum efficiency of up to 30 %. These experimental findings suggest promising prospects for the utilization of Er3+ doped fluorotellurate glass in 2.7 μm laser applications.

Dentofacial deformities and their management in prosthodontic practice

Dentofacial deformities encompass a wide range of skeletal and dental discrepancies that can significantly impact a patient's oral function, aesthetics, and overall quality of life. These deformities can arise from congenital, developmental, or acquired factors, each contributing to the complexity of diagnosis and treatment. Congenital conditions, such as cleft lip and palate and genetic syndromes, often result in significant craniofacial anomalies. Developmental disturbances, including hormonal imbalances and nutritional deficiencies, can further exacerbate these conditions. Additionally, trauma, infections, and neoplasms play a critical role in the etiology of acquired dentofacial deformities. Effective management of dentofacial deformities in prosthodontics requires a multidisciplinary approach, integrating orthodontics, oral and maxillofacial surgery, and advanced prosthodontic techniques. Diagnostic advancements, including 3D imaging and digital workflows, facilitate precise planning and customization of prosthetic solutions. Orthodontic treatment and orthognathic surgery are pivotal in correcting skeletal discrepancies and establishing a stable foundation for prosthodontic rehabilitation. Post-surgical prosthodontic interventions involve the use of high-strength ceramics, zirconia, and biocompatible implant materials to restore dental function and aesthetics. Technological advancements have revolutionized prosthodontic practice. computer-aided design and computer-aided manufacturing (CAD/CAM) technology allows for the accurate design and fabrication of prosthetic components, enhancing treatment predictability and efficiency. The development of minimally invasive techniques, such as guided implant surgery and laser applications, has reduced procedural invasiveness and improved patient outcomes. The integration of digital tools and advanced materials has significantly enhanced the precision, durability, and aesthetic quality of prosthetic restorations. Overall, the advances in prosthodontic techniques and materials have greatly improved the management of dentofacial deformities, offering patients better functional and aesthetic results. Continued innovation and research are essential to address the complex challenges associated with these deformities, ultimately enhancing patient care and outcomes in prosthodontic practice.

Effect of Biomin F toothpaste and Diode laser on remineralization of white spot lesions (in vitro study)

BackgroundWhite-spot lesions are considered an initial carious stage characterized by an outer enamel layer with significantly reduced mineralization. This study was conducted to assess the combined effect of Biomin F toothpaste and Diode laser on remineralization of white spot lesions.Materials and methodsAn invitro study conducted on a total of 30 premolars divided into three groups; Group A (Biomin F Tooth paste), Group B (Biomin F with laser application for 30 sec), Group C (Negative control). The three groups were submitted to three stages; stage 1:Baseline,stage 2:After demineralization ,and stage 3:After remineralization. In each stage, elemental analysis(calcium, phosphorus, and fluoride)was measured quantitatively using Energy Dispersive X-ray (EDX) analysis and qualitatively by micrographs using scanning electron microscope. The data were tested to find significant difference between mineral changes during stages by using (ANOVA) test and Bonferroni test.ResultsCalcium, phosphorus and fluoride ions decreased in all groups after demineralization. In stage 3, after application of remineralizing agents, Calcium ions increased significantly in groups A and B where p<.05. As regards to the phosphorus ions, a significant increase was observed in all groups with group A showed the highest gain as phosphorus level percentage change (%mass) was 56.52±18.02 . Fluoride ions increased significantly in groups A and B (p<0.05) but decreased significantly in group C. There was no statistical significant difference between group A and B (p ≥.05) in calcium, phosphorus, and fluoride level after remineralization.ConclusionWithin the limitation of the present study, we concluded that Biomin F toothpaste is promising in the repairing of white spot lesions on the surface of the demineralized enamel. Diode laser did not affect the remineralizing ability of Biomin F toothpaste.

An advanced fabrication method for Yb3+-Doped optical fibers featuring AlPO4 core glass

Ytterbium (Yb)-doped fibers using aluminophosphosilicate (Yb-APS) host glass offer significant advantages over conventional aluminosilicate (Yb-AS) fibers, such as strong photodarkening resistance, higher RE-ion solubility and lower Numerical Aperture (NA), making them ideal for high-power laser applications. However, achieving optimal performance in Yb-APS fiber fabrication poses various challenges, including maintaining a precise Al3+/P5+ ratio (1:1), minimizing the central dip in the refractive index profile (RIP), ensuring proper dopant distribution, and reducing background loss. We introduce a new fabrication method for Yb-APS fiber to address these challenges. This approach entails first synthesizing amorphous Yb³⁺: AlPO4 particles, then incorporating them into the fiber core using a hybrid technique that merges Vapor Phase Delivery (VPD) with solution doping (SD). We extensively utilized various materials and optical characterizations, including XRD, FTIR, Raman spectroscopy, FESEM, and XPS, to fine-tune the composition of Yb³⁺: AlPO4. The optical characterization of the developed preform sample, including absorption, emission, and luminescent lifetime measurements, was conducted to assess the fabrication technique's suitability. The results confirmed the successful incorporation of Yb-ions into the preform core, with peaks consistent with reported values. The fiber's attenuation loss was measured, showing approximately 10 dB/km at 1200 nm. This indicates that the particles dissolved smoothly during preform and fiber processing, resulting in minimal scattering loss in the fiber core. The developed fiber demonstrated NA of 0.1, uniform RIP along the preform length with significant reduction of the central dip formation and improved spectral performance (∼1.7X broader bandwidth) compared with an equivalent Yb-AS fiber. These findings suggest the Yb-APS fiber's overall effectiveness and structural robustness, highlighting the potential of the proposed fabrication method for high-power fiber laser applications.

Supermode lasing and light amplification in multicore bismuth-doped fiber

Multicore fibers are promising structures with specific light propagation properties, which can be managed to benefit several applications in optical communications, fiber lasers and amplifiers, high-resolution imaging, and fiber-based sensors. The current use of multicore fibers in laser technology is mainly focused on in-phase coherent beam combining in far-field regions (out-cavity) using bulk optical elements. However, this approach is challenging in terms of the power scalability of all-fiber lasers (intra-cavity), particularly with using low-gain media, where it is needed to provide mode-coupling (supermode propagation) stability along relatively long lengths. Here, we report a conceptual design and fabrication of a multicore bismuth-doped fiber that is capable of achieving light amplification and stable lasing in the E-telecom band inside the cavity using the supermode selection approach. By analysis of experimental and simulation data, it was found that the employment of the proposed design of a Bi-doped fiber provides a considerable advantage over the single-core fiber in terms of laser performance (output power, slope efficiency) in the cladding-pumped configuration. These results open up new opportunities for further advancement of the optical fiber technology towards efficient bismuth-doped fiber-integrated amplifiers and lasers for the O+E+S+C+L+U-telecom bands, which may find important applications, especially for the development of next-generation multiband optical transmission systems.

Matrix Metalloproteinase 9 (MMP-9) and Interleukin-8 (IL-8) in Gingival Crevicular Fluid after Minimally Invasive Periodontal Surgery with or without Er:YAG and Nd:YAG Laser Application.

This study aimed to evaluate alterations in the concentrations of matrix metalloproteinase-9 (MMP-9) and interleukin-8 (IL-8) within gingival crevicular fluid (GCF) extracted from the intrabony periodontal defect site before and after minimally invasive regenerative surgery, with or without supplemental laser application. The surgical procedure was performed using the modified minimally invasive surgical technique (M-MIST). Thirty-eight patients, each presenting with a single vertical defect, were randomly assigned to either the test (M-MIST + Er:YAG + Nd:YAG) or the control group (M-MIST). IL-8 and MMP-9 levels (primary outcomes of the study) were assessed prior to therapy, after 2 and 4 weeks, and 6 months following the surgical procedure by means of dedicated ELISA kits. Both procedures were clinically effective as evidenced by probing depth (PD) reduction and clinical attachment level (CAL) gain at the 6-month follow-up. No statistical differences were observed in the levels of MMP-9 and IL-8 between the groups at any time point assessed. The changes in the level of MMP-9 and IL-8 over time were not statistically significant in any group. IL-8 was positively correlated with MMP-9 in the control group throughout the study and in the test group 2 weeks and 6 months post-op. Within the limitations of this study, the additional application of Er:YAG + Nd:YAG lasers alongside the M-MIST procedure did not enhance the clinical and biochemical treatment outcomes compared to M-MIST alone.

Impact of CuO on physical, structural and optical properties of sodium-phosphate glasses

The present work is involved in the synthesize, characterization and evaluating the role of CuO on physical, structural and optical properties of 45P2O5-(55-x)Na2O-xCuO (x = 0, 1.0, 3.0 and 5.0 mol%) compositions. The as-synthesized samples are characterized by various experimental techniques such as XRD, FTIR, Raman and UV visible spectroscopy to study their suitability for laser and non-linear optical applications. The density of glasses increases whereas molar volume decreases from with the doping of CuO in place of Na2O. The amorphous nature of the prepared samples is confirmed by X-ray pattern. FTIR and Raman spectra confirm the presence of metaphosphate (Q2) and orthophosphate (Q0) structural units in the prepared glass samples which confirms that the glass network become more polymerised with the addition of CuO in place of Na2O. The optical band gap increases from 1.94 to 4.11 eV whereas refractive index decreases from 2.76 to 2.14 with increasing doping of CuO. The molar refraction decreases while metallization criteria increase with CuO doping. This glass material demonstrates promising potential for applications in non-linear optics.

Hastelloy C276/AISI SS304 dissimilar metal welding: A comparative review of the effective application of laser and Micro-GTAW

Hastelloy C276, known for its high temperature strength and corrosion resistance, is essential in the manufacture of medical devices and aerospace components. This study developed a micro-controlled GTA welding technology capable of precisely welding 0.4 mm thick dissimilar metals, Hastelloy C276 and SS304. This technology utilizes advanced digital signal processing (DSP) to control the arc time with precision up to 1/100 of a second and improves the welding quality through spot stitch and cold-welding functions. Moreover, the use of 300A inverter-type GTA welding equipment and 2 kW fiber laser welding equipment in this study improved the precision of the welding process. The effectiveness of this technology has been validated through macro-inspections and heat-affected zone (HAZ) analysis. The new welding technique demonstrates the potential to overcome existing welding limitations on thin Hastelloy C276 plates by integrating digital signal processing and rapid response control mechanisms.

Saturable absorption properties of mixed lead-tin halide perovskites and their application in near-infrared ultrafast lasers

Mixed lead–tin halide perovskites, as highly sensitive materials in the near-infrared region, hold significant potential for optoelectronic device applications. Here, mixed lead–tin halide perovskite saturable absorbers (SAs) have been developed by coupling with the side-polished surfaces of the single-mode fibers and excellent saturable absorption effects of the mixed lead–tin halide perovskite SAs have been demonstrated in the near-infrared region. By constructing the in-gap site assisted carrier transfer mode, the saturation absorption process of the mixed lead–tin halide perovskite SAs can be well explained, in which defects as in-gap sites can help the photon-generated carriers transfer into the conduction band and promote the Pauli-blocking-induced absorption bleaching in the SA. Moreover, ytterbium-doped fiber lasers based on perovskite SAs have been fabricated, and mode-locked operations at 1040 nm are achieved using the mixed lead–tin halide perovskite SA, generating ultra-short pulses with a pulse width of 683 fs, 3 dB bandwidth of 4.88 nm, signal-to-noise ratio exceeding 49.74 dB, and a repetition rate of 3.74 MHz. Our findings demonstrate that the mixed lead–tin halide perovskite SAs have excellent optical modulation capability and promising applications in the field of ultrafast photonics.

Electronic band structure and optical properties of BGaAsBi/GaAs using 16 band kp Hamiltonian

The numerical simulations of optical and electronic properties of BGaAsBi/GaAs quantum wells (QWs) are obtained by diagonalizing the 16-band kp Hamiltonian with distinct boron and bismuth compositions that exhibit multifaceted potential in 1.3–1.5 μm. It has been observed that under strain-relaxed conditions for a doping concentration of 12.5 % (B, Bi), the anticipated values of spin-orbit (SO) coupling energy (ΔSO) and the bandgap (Eg) are 302 meV and 0.952 eV, respectively. Additionally, strain interaction on band structure decreases the band gap from (Eg = 0.92eV–0.85eV), increasing dopant concentration from 8 % to 12.5 %. The consequence of incorporating both Bi and B impurity is a reduction in electron effective mass of BGaAsBi by ∼1.3 times concerning the host GaAs, enhancing the optical properties of BGaAsBi/GaAs quantum-confined heterostructures. Moreover, an increase in well-width introduced a red shift and reduced the peak amplitude of the gain spectra. In addition, for solar cell application, the onset of the fundamental absorption edge is depicted at an energy of about 0.96 eV. For laser applications, the optimum threshold current density and quality factor of BGaAsBi/GaAs quantum well achieved at room temperature are 1089 A/cm2 and 3653, respectively, at well width (w = 2.0 nm), cavity length (L = 0.5 mm), and average thickness of the active region (d = 45 nm). The variation in power density is studied with injected current density, while the quality factor is calculated with well width. The outcomes could be beneficial for future use in optical devices.

Effect of the use of low power laser in the treatment of chronic wounds: an integrative review

Objective: The objective was to identify the effects of low-power laser on the healing of chronic wounds. Method: This is an integrative literature review, carried out in the Medline / Pubmed, Cochrane Library and Virtual Health Library (VHL) databases, limited to Randomized Clinical Trials, in which 68 articles were identified, of which 19 were pre-selected and seven were included in the final sample, after checking the eligibility criteria. Results: Most articles (n = 05) included patients with injuries resulting from diabetes mellitus located in the regions of the feet and two studies addressed venous ulcers. Most of the selected studies showed that the use of low-level laser therapy was able to accelerate the tissue repair process, with a significant reduction in the wound area, showing effectiveness in promoting healing, when compared to the treatments presented in the different studies. The significant reduction in pain in the laser-treated group was also an important effect reported in some studies. The wavelength in nanometers (nm) used for laser application varied from 632.8 to 830 nm and the doses in joules (J) were from 3 to 7J / cm2. The duration of laser therapy treatment averaged 4 weeks. Conclusion: The low-power laser can be an alternative therapy in the treatment of chronic wounds in clinical practice to optimize and enhance the healing process.

Effect of Er:YAG Laser Application and Sandblasting on Shear Bond Strength of Veneering Ceramic to Zirconia Core.

Objectives: Porcelain chipping and delamination are among the shortcomings of all-ceramic restorations. This study aimed to assess the effect of laser irradiation and sandblasting on shear bond strength (SBS) of zirconia to veneering porcelain. Materials and Methods: In this in vitro, experimental study, 60 zirconia blocks were randomly divided into three groups (n=20) for surface treatment with Er:YAG laser, sandblasting, and no surface treatment (control). Each group was randomly divided into two subgroups (n=10) for porcelain application by the layering or the pressing technique. The surface roughness, SBS, and failure mode were determined and analyzed using two-way ANOVA, Tukey's HSD test, Chi-square test, and Pearson's correlation test (alpha=0.05). Results: The mean SBS was 8.16±3.66 MPa, 9.32±2.7 MPa, and 11.85±3.06 MPa in the control, laser, and sandblasting groups, respectively. The SBS was significantly different among the three groups (P=0.002). The failure mode of the three groups was not significantly different (P>0.05). The sandblasted group showed significantly higher surface roughness than the control and laser groups (P<0.001). Conclusion: Sandblasting yielded higher SBS particularly when the porcelain was applied by the layering technique. Although laser irradiation increased the SBS, the difference with the control group was not statistically significant.

Effectiveness of low-level laser therapy in reducing pain score and healing time of recurrent aphthous stomatitis: a systematic review and meta-analysis

BackgroundRecurrent aphthous stomatitis (RAS) is a common chronic inflammatory oral disease that negatively impacts the quality of life. Current therapies aim to reduce pain and healing process yet challenges such as rapid loss due to salivary flushing in topical drugs and adverse effects due to prolonged use of systemic medications require further notice. Low-level laser therapy is reported with immediate pain relief and faster healing thus preserving the potential for optimal treatment modalities. This review critically analyses and summarizes the effectiveness of LLLT in reducing pain scores and healing time of RAS.MethodsA systematic search was conducted in ScienceDirect, PubMed, and Scopus using keywords of low-level laser therapy, photo-biomodulation therapy, and recurrent aphthous stomatitis. RCTs between 1967 to June 2022, presenting characteristics of the laser and reporting pain score and/or healing time of RAS after irradiation were included. Animal studies and recurrent aphthous ulcers with a history of systemic conditions were excluded. Studies were critically appraised using the RoB 2 tool. A meta-analysis was performed using inverse variance random effects.ResultsFourteen trials with a total of 664 patients were included. Reduced pain was reported in 13 studies, while shortened healing time was presented in 4. The pooling of two studies after CO2 irradiation demonstrated faster healing time compared to placebo (MD − 3.72; 95% CI − 4.18, − 3.25).ConclusionPain score and healing time of RAS were reduced after irradiation with LLLT. RoB resulted in “some concerns” urging well-designed RCTs with larger samples to further assess each laser application for comparison.Systematic review registrationPROSPERO CRD42022355737.

Laser-Induced Koebner-Related Skin Reactions: A Clinical Overview.

The Koebner phenomenon (KP), also known as the isomorphic response, describes the process by which new lesions that are clinically and histologically identical to a patient's existing skin disease develop following trauma. Many skin diseases exhibit this characteristic, with variations that include possible, questionable, and pseudo-Koebner reactions, with the latter category occurring due to infectious agents seeding at a trauma site. Laser application, a type of controlled skin injury used for improving cutaneous lesions and skin rejuvenation, is also considered a form of trauma. This raises the question of whether controlled thermal injury can be regarded as a type of mechanical trauma capable of producing Koebner-related reactions. We conducted a literature review of cases or studies to identify laser-induced dermatoses that correspond to Koebner-related or pathergy reaction categories. As a whole, we identified nine case reports on true KPs, two cases on possible KPs, seventeen cases on laser-induced questionable KPs comprising cases of vasculitis, eczema or Meyerson reactions, and eruptive squamous atypia cases (ESA) as well as two pseudo-Koebner cases involving wart occurrences at laser application sites. Laser-induced Koebner reactions highlight several aspects of the KP. Firstly, the type of mechanical damage influences disease promotion, as different lasers are associated with different KPs. For example, hair removal lasers are linked with true and questionable KPs such as vasculitis while resurfacing lasers were found to be more connected with ESA occurrence. Secondly, the laser target is significant, with vascular laser application for port-wine stains tending to result in eczematous reactions, while hair follicle destruction can frequently lead to true KPs. Thirdly, the number of sessions matters; true KPs and eruptive squamous atypia questionable KPs typically appear after one to two sessions, whereas eczematous reactions require more sessions (at least four). Additionally, skin phototype is crucial, with darker phototypes showing a higher KP frequency as laser treatment for hypertrichosis relies on melanin absorption in the hair bulge or bulb for follicle destruction, as chromophore competes with the abundant melanin in the epidermis. Further research with larger-scale studies into trauma-specific Koebner reactions is vital for refining treatment protocols, minimizing post-laser adverse effects, and improving dermatological care outcomes.

Evaluation of Safe Insertion Angles for Spinal Needles and Safe Intensity of the Holmium:YAG Laser during Percutaneous Laser Disc Ablations in Feline Cadavers.

In the context of veterinary medicine, minimally invasive techniques for feline spinal surgery remain underexplored, particularly for percutaneous laser disc ablation (PLDA) when using the Holmium:YAG (Ho:YAG) laser. This study aimed to refine the application of the Ho:YAG laser in PLDA by determining the optimal laser intensity and safe insertion angles for the thoracic and lumbar intervertebral discs (IVDs) in cats. Through utilizing computed tomography (CT) for precise guidance, this research involved a cadaveric study of 10 cats to evaluate the spatial configurations that allow for safe needle insertions and effective laser ablation. Various energy settings of the Ho:YAG laser (20 J, 40 J, and 60 J) were tested to ascertain the balance between adequate disc vaporization and minimal adjacent tissue damage. The results demonstrate that a 40 J setting is the most effective in achieving significant disc decompression without compromising surrounding tissue integrity. Additionally, the CT scans proved crucial in confirming the accuracy of the needle placement and the safety of the laser application angles. This study established that the 40 J setting on the Ho:YAG laser, combined with CT-guided insertion techniques, offers a reliable method for PLDA, thus enhancing the safety and efficacy of feline spinal surgeries.

The [100] direction strained Ge[formula omitted]Snx nanowires with low Sn contents towards the application of SWIR or MWIR lasers

The band structures of Ge1−xSnx nanowires with low Sn contents at the Γ-valley and L-valley under the [100] direction stress are studied via effective-mass theory, and we find that Ge0.95Sn0.05 and Ge0.92Sn0.08 nanowires can be tuned to direct-bandgap semiconductors even for the stress less than 4 GPa. Moreover, as increasing the stress, the calculations of the optical gain manifest that the z direction peak gain can be enhanced sharply regardless of the diameter and Sn content since more electrons are filled at the Γ-valley. The further research shows that the FCA loss of Ge1−xSnx nanowires can almost be neglected, meanwhile remarkable and positive net peak gain along the z direction can be acquired even though electron concentration is as low as the order of 1018 cm−3, which can overcome the non-negligible FCA loss caused by electron concentration of the order of 1019 cm−3 in Ge or strain-free Ge1−xSnx nanowires.

Enhancing luminescence from visible to mid-infrared: Controllable crystallization in ZnF2-AlF3 fluoride glass-ceramics

This study presents the synthesis of innovative fluoride glass-ceramics (GCs) via a melt-quenching technique followed by heat treatment, enabling the controlled formation of ZnF2 nanocrystals within an Er3+-doped ZnF2-AlF3 fluoride glass matrix. The uniform dispersion of ZnF2 nanocrystals throughout the glass matrix was confirmed through X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Remarkably, the crystallized glass samples retained high levels of transparency. Enhanced luminescence across visible to mid-infrared spectral regions was observed in the Er3+-doped ZnF2-AlF3 based fluoride glass-ceramics compared to their precursor glass, signaling a significant improvement. These findings underscore the potential of the developed fluoride glass-ceramics as promising materials for laser applications and mark a significant step forward in the development of fluoride crystallized fibers.

Application of matrix-assisted laser desorption/ionization in the studies of phosphotungstic acid.

Phosphorotungstic acid (PTA) has many applications, especially in the field of catalysis, due to its structural properties. However, the structure of PTA is studied mainly using theoretical methods. Matrix-assisted laser desorption/ionization (MALDI) has the potential to be an effective method for the experimental study of heteropolyacids. Limitations of MALDI are the high molecular weight of the particles and the complex distribution of isotopic peak intensities. Both problems can be solved by automatically identifying observed signals by generating hypothetical molecular formulas and estimating their isotopic distributions. Phosphotungstic acid was studied under conditions of laser desorption/ionization in the absence and in the presence of the matrix. Three types of matrices were used: 2,5-dihydroxybenzoic acid in water, α-cyano-4-hydroxycinnamic acid in acetonitrile, and sinapic acid (SA) in tetrahydrofuran. Part of the peaks in the resulting mass spectra was identified using in-house developed software that implements the automated isotopic distribution brute force. The most informative mass spectra were obtained using SA as the matrix, which enabled the detection of particles containing PTA dimers for the first time. The compositions of particles incorporating PTA dimers were determined in an automated manner and can be written as [H3PW12O40]2·2H2O (m/z= 5791.2Da) and [H3PW12O40]2·4H2O (m/z = 5836.5Da). Other observed species included (WO3)n·PO3 -, HPO2·(WO3)n, and WO2·(WO3)n clusters, with the latter containing W in mixed oxidation states. The combined use of MALDI and an automated identification procedure provided valuable experimental data on the structure and fragmentation of phosphotungstic acid. To the best of our knowledge, this study was the first to report on particles containing phosphotungstic acid dimers.

Recent Advances in Fabrication and Applications of Yttrium Aluminum Garnet-Based Optical Fiber: A Review.

Yttrium aluminum garnet (YAG)-based optical fiber is one of the research hotspots in the field of fiber lasers due to its combined advantages of a wide doping range of rare earth ions and the high mechanical strength of YAG material, as well as the flexibility and small size of the fiber structure. YAG-based optical fibers and related laser devices can be used in communication, sensing, medicine, etc. A comprehensive review of YAG-based optical fibers is provided in this paper. Firstly, the fabrication processes of YAG-based optical fibers are summarized and the structure and properties of fibers are classified and compared. Secondly, according to the optical wavelength regions, rare earth-doped YAG-based optical fibers for the applications of single-frequency and mode-locked fiber lasers are summarized. Lastly, the development challenges in both the fabrication and applications of YAG-based optical fibers are discussed.