The main research content of this paper is to achieve active-passive dual-loss Q-switched based on a WS2 saturable absorber (SA) with a thickness of 1.6 nm,thereby optimizing 1.06 μm laser pulse output characteristics. The few layers of WS2 nano-film material were prepared by combining electron beam evaporation (EBE) with chemical vapor deposition (CVD). The unsaturated absorption loss of the WS2 sample is 7.3%, the modulation depth (ΔT) is calculated to be 19.2%, and the saturation power intensity(Isat) was fitted to be 1.64 MW/cm2. The prepared WS2-SA successfully achieved passive Q-switched of the laser. When the pump power is 3 W, the maximum average output power, pulse width, pulse repetition rate, single pulse energy, and peak power are 752 mW, 390 ns, 400 kHz, 1.88 μJ, and 4.82 W, respectively-utilizing the saturable absorption characteristics of WS2 to reduce the threshold of the acoustic-optic modulator (AOM) active Q-switched laser. Through comparative experiments, it is shown that the attributes of AOM+WS2 active-passive Q-switched laser have been optimized. When the AOM frequency is 10 kHz, the narrowest pulse width of the dual-loss Q-switched laser is 16 ns, which is 30.4% less than the single AOM active Q-switched laser. The peak power of the active-passive Q-switched laser is 2.24 kW, which is 29.5% higher than the former. The pulse width compression and peak power increase are significant, which is beneficial for the instantaneous energy output of the laser.
Abstract. Laser scanning devices are indispensable for material surface treatment, laser drilling, and laser marking; due to the limited scanning speed, the traditional galvanometer scanning system is increasingly unable to match the high repetition rate laser. The scanning speed of the polygon mirror scanner can reach 1000 m/s. Based on the FPGA (Field Programmable Gate Array) control system, the scanning speed of the polygon mirror scanner can be synchronized with the pulse repetition rate of the nanosecond laser so that after a single scan, there is only one laser pulse injection at each scanning position. This paper mainly studies the processing of titanium alloy templates by high-speed polygon mirror scanner and the influence of laser parameters and scanning parameters on the processing process. The processing depth will be changed by the reasonable adjustment of laser parameters. When the laser power reaches 500 W, the hole diameter can get 112 μm, the depth 156 μm, and the taper tends to be 0.325. There is a geometric relationship between scanning speed, laser pulse repetition rate, and scanning hole spacing, and different functions such as two-dimensional laser marking, laser drilling and laser scribing can be realized according to processing requirements. When the scanning speed of the polygon mirror scanner exceeds 800 m/s, the pulse repetition rate is 500 kHz, the spacing between holes is 1.6 mm, the spacing between lines is 1.6 mm, the overall scanning times are 30 times, and the surface processing of about 4000-hole positions takes only 1.5 seconds. At the end of this paper, a typical application case is presented. There are thousands or even tens of thousands of micro-holes on the surface of titanium alloy templates processed by a high-speed polygon mirror scanner. The template shows a good effect after the deposition of biological coating materials or related drugs and can be actively applied to the healing of traumatic bone tissue.
This paper mainly uses laser technology to study the back slotting of PERC (Passivated Emitter and Rear Cell) solar cells. The high-speed laser scanning device based on the polygon mirror can effectively improve the slotting efficiency of PERC solar cells in current industrial processing. The rotating speed of the polygon mirror is 11400 rpm. The focus lens adopts a long focal length of 420 mm, so the maximum scanning speed can be 1000 m/s, the laser power is 500 W, the pulse repetition rate is 500 kHz, the wavelength is 1064 nm, the pulse width is 120 ns, and the size is 100 mm × 100 mm solar cell is scanned and processed 12 times, the scanning speed is 500 m/s, the surface treatment is about 10201 micro-holes the hole depth is 130 nm, and it only takes 0.8 seconds. The theoretical and experimental research shows that this technology will significantly improve the industrial slotting efficiency of the solar cell. In addition, the passivation layer of PERC solar cells mainly adopt slotting and perforating in industry. The former technology is relatively mature but will lose much passivation film area to increase the carrier recombination rate, and the latter industrial processing efficiency is low. While sintering the back electrode, it is easy to produce a "hole" in the back electrode to increase the series resistance of the solar cell, thus affecting the conversion efficiency of the solar cell itself. In this paper, we use the polygon mirror laser scanning device to slot the back surface of the solar cell. At the same time, we also designed a "back dotted line" slotting of the solar cell. Compared with the straight-line slot, the dotted line slotting increases the solar cell's short circuit current and open circuit voltage. It ultimately improves the photoelectric conversion efficiency by 0.04%.
With the development of laser technology, laser drilling has been widely used in industrial processing, especially the manufacture of micro-hole arrays on metal or non-metal surfaces to improve the surface properties of materials. The manufacture of laser micro-hole arrays depends on high-frequency laser and high-speed scanning devices. Compared with the traditional galvanometer scanning device, the scanning speed of the polygon mirror scanner can reach 1000 m/s, which is dozens or even hundreds of times that of the galvanometer. Polygon mirror scanner combined with the high repetition rate nanosecond laser can realize the ultra-high-speed two-dimensional plane precision micro-hole arrays. High-speed laser precision drilling, especially micro-hole manufacturing, has become the core technology of high-speed laser micro-machining. Based on the FPGA control system, the scanning speed of the polygon mirror scanner can be synchronized with the pulse repetition rate of the nanosecond laser, and the dot-arrays drilling can be effectively realized. There is only one laser pulse injection at each scanning position. This paper mainly studies the effects of average laser power, laser pulse repetition rate, laser pulse width, and working defocus on laser drilling. Including hole diameter, the conical degree of each hole, and drilling efficiency. The hole diameter and the threshold energy density of material burning under different laser pulse widths were tested and compared. The changes of laser drilling aperture and taper were observed with increased laser power and single pulse energy. While the laser pulse width is 120 ns, the material burning threshold is 4.59 J/cm2, and the maximum hole radius is 50 μm. The minimum taper is 0.36. The optimized processing technology is proposed. Under the same other conditions, the hole depth and hole morphology of 0.3 mm stainless steel dot-arrays arrangement drilling, dot-arrays dislocation arrangement drilling, and dot-arrays dislocation arrangement drilling under zoom were experimentally studied. While the number of scan times is 40, the maximum hole depth of the dot-arrays staggered arrangement zoom drilling can reach 161 μm.
An intracavity optical parametric oscillator (IOPO) pumped by a continuous-wave (CW) mode-locked laser is experimentally realized. The fundamental cavity and optical parametric oscillator cavity are designed to satisfy synchronous pumping. The output characteristics of signal and idle light are measured. Because of higher fundamental photon intensity in IOPO, the threshold of IOPO is lower than that of an extra-cavity optical parametric oscillator. The spectroscopy of signal light is obtained and the wavelength of idle light can be estimated to be 3.298 μm from noncritical phase matching. Based on the intensity fluctuation mechanism of fundamental locking, the dynamical model for IOPO pumped by a CW mode-locked laser is developed. The simulated results for the temporal shape of three lights are calculated from the derived rate equations. Because of dispersion, the signal pulse width of the theory is smaller than that of the experiment with the same pump energy.
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