Mr. Duhang Zheng Profile

Duhang Zheng

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Proceedings Article | 11 October 2024 Paper

Optimizing laser active Q-switched through a few-layer WS2 passive saturable absorber

Duhang Zheng, Shipeng Liu, Shumeng Wu, Sirui Zhang, Shikun Sun, Zimu Wang

Proceedings Volume 13287, 1328706 (2024) https://doi.org/10.1117/12.3036924

KEYWORDS: Q switched lasers, Q switching, Transmittance, Pulsed laser operation, Saturable absorption, Power meters

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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(I_sat) 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.

Proceedings Article | 16 October 2023 Paper

Study on the treatment of titanium alloy template by high-speed laser polygon mirror scanning system

Shipeng Liu, Kaisheng Zhang, Duhang Zheng, Botian Zheng

Proceedings Volume 12792, 1279203 (2023) https://doi.org/10.1117/12.2687953

KEYWORDS: Laser processing, Pulsed laser operation, Alloys, Laser scanners, Laser drilling, Polygon scanners, Laser applications

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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.

Proceedings Article | 16 October 2023 Paper

Research on laser high-speed slotting the PERC solar cell

Shipeng Liu, Duhang Zheng, Botian Zheng, Kaisheng Zhang

Proceedings Volume 12792, 1279204 (2023) https://doi.org/10.1117/12.2687954

KEYWORDS: Solar cells, Passivation, Laser processing, Pulsed laser operation, Silicon, Galvanometers

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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%.

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