[en] Utilization of hydrogen energy has many attractive features, including energy renewability, flexibility, and zero green house gas emissions. In this current research the production and the enhancement of hydrogen from the NaOH mixed water have been investigated under the action of diode pumped solid state laser with second harmonic of wavelength 532 nm. The efficiency of the hydrogen and oxygen yields was found to be greater than the normal Faradic efficiency. The parametric dependence of the yields as a function of laser irradiation time, Laser focusing effect and other parameters of the electrolysis fundamentals were carefully studied. (author)

[en] The determination of stimulated emission cross sections at various temperatures is reported. Neodymium doped yttrium orthovanadate crystal (Nd:YVO_4) was employed as a gain medium. The temperature of the crystal holder varied between 20 and 60 °C. The cross section was determined based on laser performance. The slope efficiency of the diode end-pumped Nd:YVO_4 laser system decreased from 40.2% to 31.7%, while the threshold power increased from 0.744 to 1.028 W. The far-field beam diameter increased linearly with the absorbed pump power at a constant temperature. There was no correlation between the rate of change of the beam diameter with temperature due to mechanical stress fluctuation. The stimulated emission cross section was found to decrease at a rate of  −0.45% °C"−"1, which concurs with previous works. The stimulated emission cross section of various solid-state gain mediums can be determined through this method. (letter)

[en] An aluminum substrate has been alloyed with an iron and copper mixture by a laser induced plasma technique. The nanosecond pulse duration and the high plasma temperature expose the interacting materials to decalescent and recalescent regions, contributing to the formation of new chemical composites such as AlFeCu, AlFe, AlCu and CuFe. The microstructure of the alloyed surface is observed to be heterogeneous, with no crack formation and with few pores. The hardness of the laser treated surface is 103 HV, seven times harder than that of the substrate (15 HV) at a corresponding super lateral energy of 5282 mJ cm⁻². (letter)

[en] There is a typewriting mistake in our previous report [Chin. Phys. Lett. 32, 4 (2015) 043201], the name of the fourth author M. Bohadoran should be M. Bahadoran. We note that this mistake does not affect the conclusion of our report, and apologize for any inconvenience for readers caused by our oversight. (paper)

[en] This paper reports the demonstration of ultrafast fiber laser in a simple erbium-doped fiber (EDF) laser that employed a carbon nanotube (CNT) thin film saturable absorber (SA) to generate a stable soliton pulse. The repetition rate of 10.8 MHz pulse consistently achieved has narrowest pulse width of 640 fs and 1555.78 nm central wavelength for an hour operation in room temperature. This proposed setup has the capability for reliable and stable system features. (paper)

[en] The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Ablation and excitation of the graphite material is performed by using an 1064 nm Nd:YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emission. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations. (authors)

[en] Liquid crystal physical gels were (thermally) prepared with cholesteryl stearate as a gelator in nematic liquid crystal, 4-cyano-4′-pentylbiphenyl. The electro-optical performance of liquid crystal physical gels is almost entirely dependent on the gels' inherent morphology. This study involved an empirical investigation of the relationships among all of the gelation temperature, morphology, and electro-optical properties. Besides continuous cooling at room temperature, isothermal cooling was also performed at both 18 and 0 °C, corresponding to near-solid and solid phases of 4-cyano-4′-pentylbiphenyl respectively. Nevertheless, the liquid crystal physical gel was also isothermally rapidly cooled using liquid nitrogen. Polarizing optical microscopy showed that the gel structure became thinner when isothermal cooling was carried out. These thinner gel aggregates then interconnected to form larger liquid crystal domains. Moreover, it was also revealed that the gel networks were randomized. Electron spin resonance results showed that the liquid crystal director orientation was severely randomized in the presence of gel networks. Conversely, isothermal cooling using liquid nitrogen generated a higher liquid crystal director orientation order. The 6.0 wt% cholesteryl stearate/4-cyano-4′-pentylbiphenyl physical gel that was isothermally cooled using liquid nitrogen showed the lowest response time in a twisted nematic mode optical cell. - Graphical abstract: Liquid crystal physical gel was prepared using nematic liquid crystal, 4-cyano-4′-pentylbiphenyl and cholesteryl stearate as gelator. Isothermal cooling at lower temperature produced thinner gel network and larger liquid crystal domain. - Highlights: • 5CB nematic liquid crystal was successfully gelled by cholesteryl stearate gelator. • The morphology of gel network was controlled by different cooling conditions. • Thinner gel network was formed by the rapid cooling using liquid nitrogen. • Enhanced electro-optical properties of liquid crystal physical gel were achieved.