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Abstract: By using the extended Huygens–Fresnel principle, the analytical expressions for the cross-spectral density matrix of the partially coherent Laguerre–Gaussian vector beams with vortices propagating through atmospheric turbulence are derived theoretically in detail, and used to study the intensity and polarization properties of partially coherent Laguerre–Gaussian beams in atmospheric turbulence. It is found that the variations of the intensity of the completely polarized part and the completely unpolarized part are closely related with the strength of atmospheric turbulence, the topological charge and the beam width in the source plane. The spectral degree of polarization of the partially coherent Laguerre–Gaussian vector beams with vortices tends to a certain value that is different from the source plane after a sufficiently long propagation distance in turbulent atmosphere. Furthermore, this value is dependent of the strength of turbulent atmosphere, the topological charge and the beam width in the source plane. The polarization property of the partially coherent Laguerre–Gaussian vector beams with vortices can be modulated by modulating the topological charge and the beam width in the source plane. [Copyright &y& Elsevier]

This paper reports on the characterization of a diode-side-pumped CW Nd:YAG laser. A side-pumped configuration with 9 laser diodes is used for the laser. Pump light is directly coupled into the Nd:YAG rod without focusing lenses and the pump light distribution in the Nd:YAG rod was calculated. A maximum output power of 150 W in multimode operation is obtained for a pumping power of 400 W. The optical–optical efficiency is 37%. Output power of the laser under different output couplers, resonator lengths and temperatures of the cooling water have been studied. [Copyright &y& Elsevier]

• A novel combined pulse laser (CPL) was proposed for drilling the alumina ceramic. • The keyhole drilled by the nanosecond pulses could enhance the absorptivity. • The fluence of the millisecond pulses for drilling was decreased to 57 J/cm2. • The CPL drilling had obvious advantages in reducing hole cracks and diameter. Ceramic with outstanding mechanical and physical properties has been widely used in various engineering applications. The low processing efficiency and quality of the conventional millisecond laser prevents the broad applications of laser drilling technology in ceramic. In this paper, a novel combined pulse laser (CPL) that consisting of an initial nanosecond pulse train followed by a millisecond pulse train was proposed for drilling the alumina ceramic. Experimental results showed that the pre-treatment of the initial nanosecond pulses could introduce a keyhole with a depth about 21.5 μm, which improved the performance of the subsequence millisecond pulses to reduce the diameter and cracks of the hole. In addition, the effect of the CPL drilling of alumina ceramic under different spot sizes was systematically analyzed. It was shown that the keyhole ablated by the initial nanosecond pulses could be used to limit the hole diameter even the millisecond laser had a bigger spot size. Ultimately, it was demonstrated that the diameter, defects and taper angle of the hole could all be decreased by increasing the repetition rate of the subsequent millisecond pulses. The millisecond pulses with a single pulse energy density about 57 J/cm2 could drill through the alumina ceramic, which was two orders of magnitude lower than conventional millisecond laser. The research results have an important guiding for improving the processing efficiency and quality of millisecond laser, especially for the laser processing of ceramic materials. [ABSTRACT FROM AUTHOR]

• Single-scan high-efficiency cleaning of the rubber curing die with non-uniformly deposited contaminants was achieved. • Laser cleaning of the net cracks on the chromium layer of the die was firstly investigated. • The cleaning mechanism of different thickness contaminants was systematically analysed. Removal of rubber contaminants from chrome-plated die with slots was studied using an acousto-optic Q-switched Nd:YAG nanosecond pulsed laser with an average power of 100 W. The contaminants deposited non-uniformly on the die can be distinguished as rubber particles with a nominal diameter of 10 μm, located mainly in the plane region (PR), while a thick rubber layer up to 50 μm can be discovered in the slot region (SR). Results show that, by positive defocusing the laser with single pulse energy density of 0.97 J/cm2 and adding the argon gas, single-scan high-efficiency cleaning of the slots could be achieved, and the net cracks on the chromium layer could be cleaned too. The optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM) were used to investigate the surface of the die before and after cleaning. [ABSTRACT FROM AUTHOR]