Laser shock peening is an effective surface technology for improving the surface mechanical properties of metals. Many studies have been performed to process different kinds of metallic material that can induce compressive residual stress in the top layer of samples, which would extend the fatigue life of metal parts in the industry. The titanium alloy samples are treated by laser shock peening with water layer as constraint layer and without protective coating in this research, after which the titanium alloy samples are observed and analyzed with a scanning electron microscope, hardness tester, laser confocal microscope, and wear tester. The surface roughness, surface microstructure, and other properties of untreated and treated titanium alloy are compared to study the effect on titanium alloy of laser shock peening process without protective coating.
At present, laser cutting has emerged as a new technology in the field of glass cutting to achieve a good quality and high efficiency, that is believed to have a very broad application prospect. In this report, the glass cutting by picosecond laser with a high peak power and a long focal-depth Bessel beam was studied. The maximum power of laser is chosen to be 50 W with a spot size of 2 mm, pulse width of 10 ps, and wavelength of 1064 nm. The frequency is adjustable in the range of 50 KHz to 200 KHz. The factors affecting the cutting roughness was analyzed, including the focus position, speed, and power. Meanwhile, the glass is split by a carbon dioxide laser with the wavelength of 10.6 μm and maximum power is 100 W, which breaks due to internal stress induced by heating. By adjusting the speed, power and focusing position, the good processing parameters for the ultra-white glass with thickness of 4 mm were found. High quality cutting with minimum edge breakage less than 3 μm is confirmed by microscope. Moreover, nonstandard-shaped cutting and straight line cutting with a high speed of 300 mm/s have also achieved in this work. All results demonstrates that ultra-fast laser is a promising tool for glass cutting.
As the third generation of photovoltaic cell technology, the Perovskite Solar Cells (PSCs) have strong theoretical advantages compared with discrystalline silicon and thin film cells because of their material characteristics. In the formation of the series structure of perovskite cells, different film layers need to be marked at different positions. The scribing of functional layers can be done by mask plate, chemical etching, mechanical or laser scribing. Laser scribing can produce finer scribing areas. At present, laser scribing has gradually replaced other scribing methods and become the main scribing methods. In this paper, laser scribing for the realization of all the P1, P2, and P3 scribes are reported by optical fiber femtosecond laser with output wavelengths of 532 nm, and pulse width is adjustable at 300 fs. The better processing parameters are found for the scribing speed of 2000 mm/s, and the laser power of 1.8 W for the P1 scribe. High precision scribing with slit width less than 10 μm is obtained by optimizing scribing speed and laser power. All the results indicate that laser scribing would play an important role in achieving high performance PSCs modules in which the interconnects.
We demonstrate comparatively the laser performance of 970 nm laser diode (LD) side-pumped Er:YSGG crystals with a length of 85 mm and diameters of 2, 3, and 4 mm. The maximum average powers of 25.18, 25.74, and 20.41 W are achieved at 150 Hz and 200 μs, corresponding to the slope efficiencies of 30.01%, 31.47%, and 24.38%, respectively. The experimental results show that the Er:YSGG crystal rod with a diameter of 2 mm has no obvious advantage in laser output at low frequency and low pump power because the gain volume is small and the pump power cannot be fully absorbed, resulting in the gain saturation phenomenon. However, it exhibits the best laser output under high repetition rate and high pump power. The average power of 16.47 W obtained at 500 Hz is still not saturated. The beam quality factors M2 in the x and y direction are determined to be 3.15/3.12, respectively, which is significantly better than those of the rods with diameters of 3 and 4 mm. All the results indicate that the crystal rod with a smaller diameter has better thermal management due to its larger specific surface area and better cooling ability, which is conducive to improving laser performance under the high repetition rate and high pump power operation.
We demonstrate a high-peak-power and narrow pulse mid-infrared (MIR) laser with xenon-lamp pumping and La3Ga5SiO14 (LGS) Q-switching on the Cr,Er:YAP crystal grown by Czochralski method. X-ray powder diffraction and x-ray rocking curves suggest the crystal has high crystalline quality. Segregation coefficients of the Cr3 + and Er3 + in the as-grown Cr,Er:YAP crystal are 4.96 and 1.07, respectively. The absorption and fluorescence spectra indicate that the Cr,Er:YAP crystal is a promising material for MIR laser by xenon-lamp pumping. The fluorescence lifetimes of the upper (I11/24) and lower (I13/24) laser levels are 0.86 and 3.57 ms, respectively. A maximum energy of 632 mJ is acquired at 5 Hz by xenon lamp pumping. By the LGS electro-optic Q-switching technology, single pulse energy of 148.6 mJ is achieved at 5 Hz with a pulse width of 35.4 ns and peak power of 4.2 MW. The results show that the LGS Q-switched Cr,Er:YAP crystal pumped by xenon lamp possesses potential application as a short-pulse and high-energy laser device.
We demonstrate and compare the absorption spectra, laser performance and thermal lens effect of a-, b-, and c-cut 15 at% Er:YAP crystal in detail. The Er:YAP crystal along a-axis possesses larger absorption coefficient, but the b- axis Er:YAP crystal exhibits better laser performance. A maximum output power of 916 mW is achieved in the b-axis Er:YAP crystal with slope efficiency of 16.0%. As the important factors that affecting the laser performance of solid-state laser, the thermal lens effect of Er:YAP crystal is studied by simulate the temperature distributions and the thermally induced focal lengths. The result indicates that the b-cut Er:YAP crystal has a weaker thermal lens effect due to its high thermal conductivity and low temperature refractive index coefficient. All the result indicate that the b-cut Er:YAP crystal shows a better laser performance, which is a promising candidate for high performance CW mid-infrared laser.
We demonstrate the performance of a 968-nm laser-diode (LD) side-pumped Er,Pr:YAP laser in free-running and electro-optical (EO) Q-switched modes with emission at 2.7 μm, respectively. In the free-running mode, a maximum power of 11 W is achieved at a working frequency of 150 Hz and a pulse width of 200 μs, corresponding to the single pulse output energy of 73.3 mJ and slope efficiency of 13.3%. In the EO Q-switching mode, a giant pulse laser is obtained with pulse energy of 20.5 mJ, pulse width of 61.4 ns, and peak power of 0.33 MW at the highest working frequency of 150 Hz, corresponding to the energy extraction efficiency of 71.4%. In addition, dual-wavelength laser at 2713 and 2732 nm and beam quality factors Mx2/My2 of 6.62/6.66 are measured, respectively. The results indicate that a 2.7-μm laser with a high repetition rate and high peak power can be realized through LD side-pumped and EO Q-switched Er,Pr:YAP crystal.
We present a high-quality Cr,Nd:YAG crystal with 1.0 at. % Cr3 + and 1.1 at. % Nd3 + grown successfully by the Czochralski method. Spectroscopy results indicate that codoped Cr3 + ions are advantageous for improving pumping efficiency. The maximum average power of 20.24 W operated at 40 Hz and 1.06 μm is obtained on the Cr,Nd:YAG crystal, with electrical-to-optical and slope efficiencies that correspond to 3.00% and 3.77%. Meanwhile, the maximum average power of only 13.32 W is obtained on the Nd:YAG crystal, with the electrical-to-optical and slope efficiencies of 1.97% and 2.47%, respectively. In addition, the laser beam quality of the Cr,Nd:YAG crystal is comparative with that of the Nd:YAG crystal. Therefore, the Cr,Nd:YAG is a promising laser crystal with higher laser performance and stronger radiation-resistant ability than the Nd:YAG crystal. Thus, the Cr,Nd:YAG crystal can be applied to high-power systems and radiant environments.
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