High-concentration Er3+ ions singly doped GaTaO4 single crystal for promising all-solid-state green laser and solid-state lighting applications

Exploring new visible laser crystals is of great significance to the development of diode pumped all-solid-state visible lasers and solid-state lightings. In this work, high concentration (10 at.%) Er3+ ions...

In-situ ellipsometry measurements on the phase segregation of mixed halide lead perovskites

Mixed halide lead perovskite such as methylammonium lead iodide bromides MAPb(BrxI1-x)3 have emerged as one of the most promising materials of future solar cells, offering high power conversion efficiencies and bandgap tunability. Among other factors, the reversible phase segregation under even low light intensities is still limiting their potential use. During this process, the material segregates locally into iodide-rich and bromide-rich phases, lowering the effective bandgap energy. While several studies have been done to illuminate the mechanism and suppression of phase segregation, fundamental aspects remain unclear. Phase compositions after segregation vary extensively between different studies and the exact amounts of phases often remain unmentioned. For iodide-rich phases, the end-point compositions at around x=0.2 are widely accepted but the proportion of the phase is difficult to measure. In this report, we observe the phase segregation using spectroscopic ellipsometry, a powerful, nondestructive technique that has been employed in the study of film degradation before. We obtained dynamic ellipsometric measurements from x=0.5 mixed halide lead perovskite thin films protected by a polystyrene layer under green laser light with a power density of ~11 W/cm2. Changes in the bandgap region can be correlated to the changes in composition caused by phase segregation, allowing for the kinetics to be observed. Time constants between 1.7(± 0.7)×10-3 s-1 for the segregation and 1.5(± 0.6)×10-4 s-1 for recovery were calculated. We expect ellipsometry to serve as a complementary technique to other spectroscopies in studying mixed-halide lead perovskites phase segregation in the future.

Effectiveness of high-intensity laser light for treating large kidney stones

Introduction. This work analyzes efficacy, convenience, and safety of a high-energy laser light technique for destructing large kidney stones in patients with nephrolithiasis in comparison to other contact methods of nephrolithotripsy.Material and methods. The effectiveness of contact laser nephrolithotripsy is compared to that of hydropneumatic and ultrasonic lithotripsy. Holmium green laser light was used in this laser procedure. For other techniques, Swiss LithoClast Master devices were used. The authors have analyzed outcomes obtained after operating on 73 patients with large and complex kidney stones.Results. To evaluate the effectiveness, basic parameters were taken (degree of kidney cleaning of stones and their fragments, probability of migration of stone fragments, blood loss, duration of surgery, complications, etc.). In addition, the correlation between basic parameters was obtained and analyzed.Conclusion. The present trial has shown that laser contact lithotripsy is the most optimal technique for destructing large and complex kidney stones in comparison to traditional modalities such as contact hydropneumatic and ultrasonic lithotripsy. It takes more time but provides more effective cleaning from calculi.

Prediction of Surface Plasmon Resonsnce and More Accurate Representation of Absorption Features Both Below and Above the Bandgap in ZnO Nanorods array – Au Heterostructures

Well-oriented zinc oxide nanorods (ZnO NRs) arrays have been grown by low temperature chemical bath deposition on seeded substrates. A gold thin film has obliquely been deposited by DC magnetron sputtering on the ZnO NRs array. The structure, mophology/ chemical identity, vibrational identity have been studied by X-ray diffraction (XRD), field effect- scanning electron microscope/ energy dispersive X-ray spectroscopy (FE-SEM/EDX) and Raman spectroscopy, respectively. The FCC structure of Au is formed on vertically oriented ZnO NRs-array. The wavelength dependent photocurrent of ZnO NRs array-Au heteronanostructure (HNS) was evaluated by photogain response under red, green and blue laser illuminations. Surface plasmon excitation activates selective response to green laser exposure. An analytical dispersion formalism has been constructed to fit experimental absorption spectrum over wide spectrum range and to extract precise bandgap energy, subband tailing, dielectric constant and carrier effective mass. The proposed model exploits the Frouhi–Bloomer (FB) parameterization and Gaussian oscillator dispersion to the complex dielectric function for Au decorated ZnO NRs array. Sharp variation in the optical absorption around the bandgap edge and the absorption behavior beyond the bandgap edge are covered as well. It is surprising that the surface plasmon resonance (SPR) is included without new formalism. The new model has been satisfactorily tested on CuO optical absorption.