Journals > > Topics > Lasers and Laser Optics
Lasers and Laser Optics|3122 Article(s)
Discrete Path Nd∶YAG Innoslab Laser Amplifier Operating at 2 kHz Repetition Rate
Yilan Chen, Jiqiao Liu, Mingjian Wang, Xiao Chen, and Xiaolei Zhu
A compact, discrete path Nd:YAG Innoslab laser amplifier system with novel eight-pass arrangement is developed. An electro-optic Q-switched oscillator using Nd∶YVO4 crystal as gain medium is used as the seed laser. With a seed laser power of 2.7 W at a repetition rate of 2 kHz, the amplified laser power of more than 13 W is achieved successfully with the pulse width of 15.5 ns, and the corresponding extraction efficiency is 14.6%. The experimentally measured laser beam quality factors are less than 1.7 and 1.5 in the x and y directions, respectively. Self-lasing and amplified spontaneous emission (ASE) are not observed at the maximum pump power with discrete-path laser amplifier configuration. A compact, discrete path Nd:YAG Innoslab laser amplifier system with novel eight-pass arrangement is developed. An electro-optic Q-switched oscillator using Nd∶YVO4 crystal as gain medium is used as the seed laser. With a seed laser power of 2.7 W at a repetition rate of 2 kHz, the amplified laser power of more than 13 W is achieved successfully with the pulse width of 15.5 ns, and the corresponding extraction efficiency is 14.6%. The experimentally measured laser beam quality factors are less than 1.7 and 1.5 in the x and y directions, respectively. Self-lasing and amplified spontaneous emission (ASE) are not observed at the maximum pump power with discrete-path laser amplifier configuration.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914011 (2024)
Microstructure and Mechanical Properties of TiAl Alloy Prepared by Laser Melting Deposition
Feng Zhang, Hangyu Yue, Bingbing Sun, Ruifeng Li, Haisheng Zhao, Youxing Yao, and Yibin Pang
A dense and crack free Ti-48Al-2Cr-2Nb alloy (TiAl alloy) with a height of 30 cm is prepared using laser melting deposition (LMD) method with preheating process, and the internal defects, microstructure, phase composition and mechanical properties of the alloy are studied. The micro/nano CT (computed tomography) testing results show that the density of the TiAl alloy formed after preheating is 99.996% and the number of pores is significantly less than that of the TiAl alloy formed without preheating. The microstructure of the sample is lamellar structure, metastable Weinstein structure, and feathery structure observed by optical microscopy and scanning electron microscopy. Only slight segregation of Cr and Nb elements is observed through energy spectrometer equipment. Electron back scatter diffraction experiment is conducted on the sample, and the main phase composition of the sample is γ phase, containing a small amount of α2 and B2 phase. The average kernel average misorientation (KAM) value of TiAl alloy formed after preheating is slightly higher than that of the alloy formed without preheating. In addition the hardness and tensile properties of the dense and crack free alloy are tested, the alloy has a microhardness of 350 HV0.5, a tensile strength of 497 MPa, and an elongation of 0.49%. Its tensile properties are higher than those of traditional casting TiAl alloy. Therefore, the preheating process has important guiding significance for the LMD formation of high-density and crack free TiAl alloys. A dense and crack free Ti-48Al-2Cr-2Nb alloy (TiAl alloy) with a height of 30 cm is prepared using laser melting deposition (LMD) method with preheating process, and the internal defects, microstructure, phase composition and mechanical properties of the alloy are studied. The micro/nano CT (computed tomography) testing results show that the density of the TiAl alloy formed after preheating is 99.996% and the number of pores is significantly less than that of the TiAl alloy formed without preheating. The microstructure of the sample is lamellar structure, metastable Weinstein structure, and feathery structure observed by optical microscopy and scanning electron microscopy. Only slight segregation of Cr and Nb elements is observed through energy spectrometer equipment. Electron back scatter diffraction experiment is conducted on the sample, and the main phase composition of the sample is γ phase, containing a small amount of α2 and B2 phase. The average kernel average misorientation (KAM) value of TiAl alloy formed after preheating is slightly higher than that of the alloy formed without preheating. In addition the hardness and tensile properties of the dense and crack free alloy are tested, the alloy has a microhardness of 350 HV0.5, a tensile strength of 497 MPa, and an elongation of 0.49%. Its tensile properties are higher than those of traditional casting TiAl alloy. Therefore, the preheating process has important guiding significance for the LMD formation of high-density and crack free TiAl alloys.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914010 (2024)
Performance Improvement of 1550 nm Pulse Laser Diode Transmitter Module Using Equivalent Electrical Circuit Analysis
Li Li, Lin Li, Jiaju Ying, Gang Li, and Yuanbo Wang
To adapt the requirements of high power and narrow pulse width of detection laser in the active detection application for the eye-safe laser, a method for improving the performance of 1550 nm pulse laser diode transmitter module using equivalent circuit model analysis is proposed. The equivalent circuit model is established based on the specific laser parameters, and the model is introduced into the pulse drive circuit of the transmitter module. The key factors affecting the output characteristics of high power, narrow pulse laser are obtained through simulation analysis. The optimized two package lasers are connected to the pulse laser transmitter module to test the output laser pulse. The measured results are consistent with the simulation results, it is proved that the equivalent circuit analysis method can be used to evaluate and optimize the performance of the laser transmitter module. Finally, the optical pulse with the maximum output power over 20 W and the pulse width less than 10 ns is obtained that realizing laser output with high power and narrow pulse. To adapt the requirements of high power and narrow pulse width of detection laser in the active detection application for the eye-safe laser, a method for improving the performance of 1550 nm pulse laser diode transmitter module using equivalent circuit model analysis is proposed. The equivalent circuit model is established based on the specific laser parameters, and the model is introduced into the pulse drive circuit of the transmitter module. The key factors affecting the output characteristics of high power, narrow pulse laser are obtained through simulation analysis. The optimized two package lasers are connected to the pulse laser transmitter module to test the output laser pulse. The measured results are consistent with the simulation results, it is proved that the equivalent circuit analysis method can be used to evaluate and optimize the performance of the laser transmitter module. Finally, the optical pulse with the maximum output power over 20 W and the pulse width less than 10 ns is obtained that realizing laser output with high power and narrow pulse.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914009 (2024)
Microstructure Evolution and Properties of WC/Ni Based Coating on the Surface of 12CrMoV Alloy Steel by Laser Cladding
Jitai Han, Qingfeng Xia, Keqing Wang, and Guoxiang Hua
To solve the problems of wear and corrosion failure in cold-working die steel during long-term service, Ni60 coatings with different WC contents are prepared on 12CrMoV substrate using laser cladding technology. The forming characteristics, microstructure, mechanical properties, and corrosion resistance of the coatings are characterized using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, friction and wear testing machines, and electrochemical workstations. The results indicate that the additive amount of the WC can change the solidification characteristics of the melt pool, thereby reducing the width of the coatings and increasing the depth of the coatings. When the additive amount of the WC is 30% (mass fraction), the hardness of the coating is 853 HV0.3, and the average friction coefficient is only 0.467. It has excellent mechanical properties, but the toughness of the coating decreases, leading to the formation of pores during the solidification process, which reduces the corrosion resistance of the coating. When the additive amount of the WC is 10% and 20% respectively, the size of the grain structure is refined, the grain boundary area is reduced, and it has excellent corrosion resistance. When the additive amount of the WC is 20%, the corrosion current density of the coating is only 3.65 × 10-5 A/cm2, and the mechanical properties are only slightly lower than the coating obtained with 30% WC additions. Therefore, this study explored suitable WC/Ni60 coatings for wear and corrosion environments, determined the optimal additive amount of the WC, expanded the application range of WC/Ni60 coatings in mold steel, and has guiding significance for engineering practice. To solve the problems of wear and corrosion failure in cold-working die steel during long-term service, Ni60 coatings with different WC contents are prepared on 12CrMoV substrate using laser cladding technology. The forming characteristics, microstructure, mechanical properties, and corrosion resistance of the coatings are characterized using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, friction and wear testing machines, and electrochemical workstations. The results indicate that the additive amount of the WC can change the solidification characteristics of the melt pool, thereby reducing the width of the coatings and increasing the depth of the coatings. When the additive amount of the WC is 30% (mass fraction), the hardness of the coating is 853 HV0.3, and the average friction coefficient is only 0.467. It has excellent mechanical properties, but the toughness of the coating decreases, leading to the formation of pores during the solidification process, which reduces the corrosion resistance of the coating. When the additive amount of the WC is 10% and 20% respectively, the size of the grain structure is refined, the grain boundary area is reduced, and it has excellent corrosion resistance. When the additive amount of the WC is 20%, the corrosion current density of the coating is only 3.65 × 10-5 A/cm2, and the mechanical properties are only slightly lower than the coating obtained with 30% WC additions. Therefore, this study explored suitable WC/Ni60 coatings for wear and corrosion environments, determined the optimal additive amount of the WC, expanded the application range of WC/Ni60 coatings in mold steel, and has guiding significance for engineering practice.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914008 (2024)
Tunable Multi-Wavelength Brillouin-Erbium-Doped Random Fiber Laser
Haiyue Pang, Xiangjie Qin, Jiateng Zheng, Zhiyong Tao, and Yaxian Fan
A tunable multi-wavelength Brillouin-erbium-doped random fiber laser with a half-open cavity is proposed and experimentally demonstrated. It uses the backward Rayleigh scattering in the long single-mode fiber to provide random distributed feedback, and the stimulated Brillouin scattering and erbium-doped fiber to provide laser gain. In this simple laser device, stabilized 13-order Stokes light and 5-order anti-Stokes light can be obtained. By adjusting the wavelength of Brillouin pump, the random laser wavelength tuning in the range of 1550.5?1565.5 nm is realized. In addition, the wavelength fluctuation range of 1?10 orders' Stokes light is 0?0.008 nm, and the corresponding peak power fluctuation range is 0?2.28 dB, which prove that the laser has high wavelength and power stability. The results show that the laser has the advantages of simple structure, large numbers of spectral line orders, wide tunable wavelength range and high stability, which makes it has broad application prospects in many fields, such as dense wavelength division multiplexing optical communication systems, microwave photonics, precision metrology, fiber sensing and so on. A tunable multi-wavelength Brillouin-erbium-doped random fiber laser with a half-open cavity is proposed and experimentally demonstrated. It uses the backward Rayleigh scattering in the long single-mode fiber to provide random distributed feedback, and the stimulated Brillouin scattering and erbium-doped fiber to provide laser gain. In this simple laser device, stabilized 13-order Stokes light and 5-order anti-Stokes light can be obtained. By adjusting the wavelength of Brillouin pump, the random laser wavelength tuning in the range of 1550.5?1565.5 nm is realized. In addition, the wavelength fluctuation range of 1?10 orders' Stokes light is 0?0.008 nm, and the corresponding peak power fluctuation range is 0?2.28 dB, which prove that the laser has high wavelength and power stability. The results show that the laser has the advantages of simple structure, large numbers of spectral line orders, wide tunable wavelength range and high stability, which makes it has broad application prospects in many fields, such as dense wavelength division multiplexing optical communication systems, microwave photonics, precision metrology, fiber sensing and so on.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914007 (2024)
Polarization Synchronization and Desynchronization Dynamics of Mode-locked Fiber Lasers
Zhiwei Huang, Qianqian Huang, Zinan Huang, Weixi Li, Lilong Dai, Mingjiao Wang, Yuze Dai, Qing Wang, Zhijun Yan, Sergeyev Sergey, and Chengbo Mou
In this study, using a nonlinear-polarization-rotation (NPR) mode-locked fiber laser with positive dispersion as a testbed, the polarization characteristics of the pulse are analyzed in both complete mode-locked and composite mode-locked states. The switching from dissipative soliton (DS) and noise like pulse (NLP) can be achieved by making simple modifications to the polarization controllers (PCs). Under a fixed pump power, only adjusting the PCs can obtain a composite mode-locked state caused by the spontaneous switching of pulse states. By comparing and analyzing the polarization characteristics of the pulses in the two mode-locked states, it is observed that the synchronization of the longitudinal modes corresponds to the complete synchronization of the orthogonal polarization components. Whereas, the composite mode-locked of the longitudinal modes in partial synchronization corresponds to the partial synchronization of the orthogonal polarization components. It is proved experimentally that the orthogonal polarization component controls the synchronization between the longitudinal modes. This work is of significant importance to understanding the emergence of complex dynamics in mode-locked lasers and developing stable laser dynamics technology. In this study, using a nonlinear-polarization-rotation (NPR) mode-locked fiber laser with positive dispersion as a testbed, the polarization characteristics of the pulse are analyzed in both complete mode-locked and composite mode-locked states. The switching from dissipative soliton (DS) and noise like pulse (NLP) can be achieved by making simple modifications to the polarization controllers (PCs). Under a fixed pump power, only adjusting the PCs can obtain a composite mode-locked state caused by the spontaneous switching of pulse states. By comparing and analyzing the polarization characteristics of the pulses in the two mode-locked states, it is observed that the synchronization of the longitudinal modes corresponds to the complete synchronization of the orthogonal polarization components. Whereas, the composite mode-locked of the longitudinal modes in partial synchronization corresponds to the partial synchronization of the orthogonal polarization components. It is proved experimentally that the orthogonal polarization component controls the synchronization between the longitudinal modes. This work is of significant importance to understanding the emergence of complex dynamics in mode-locked lasers and developing stable laser dynamics technology.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914006 (2024)
Polarization Characterization of Fluorescence Resonance Energy Transfer Optofluidic Lasers
Jiaqi Zhao, Tingting Zhang, Tianjun Zhang, Wenjie Wang, and Shaoding Liu
A pair of fluorescent molecules capable of producing fluorescence resonance energy transfer (FRET) were used as donor and acceptor dyes. The polarization properties of FRET optical microfluidic lasers were investigated based on the G-quadruplex structure of deoxyribonucleic acid (DNA) molecules using a Fabry-Perot (F-P) microcavity as an optical resonance cavity. In the experiment, five solutions of DNA of varying K+ concentrations (whose molecular ends are each labeled with a pair of fluorescent dyes that can produce FRET) were studied and excited with linearly polarized pump light, and the ratio of the slope of the laser threshold curve of the acceptor in the parallel polarization direction (parallel to the pump light polarization direction) and the slope of the laser threshold curve (SER) in the vertical polarization direction (vertical to the pump light polarization direction) was used as the detection signal of the laser polarization of the acceptor. Findings indicate that as the K+ content in the DNA solution increases, the pumping threshold of the acceptor laser decreases, energy conversion efficiency improves, and the slope ratio of the acceptor laser reduces, leading to decreased polarization. A pair of fluorescent molecules capable of producing fluorescence resonance energy transfer (FRET) were used as donor and acceptor dyes. The polarization properties of FRET optical microfluidic lasers were investigated based on the G-quadruplex structure of deoxyribonucleic acid (DNA) molecules using a Fabry-Perot (F-P) microcavity as an optical resonance cavity. In the experiment, five solutions of DNA of varying K+ concentrations (whose molecular ends are each labeled with a pair of fluorescent dyes that can produce FRET) were studied and excited with linearly polarized pump light, and the ratio of the slope of the laser threshold curve of the acceptor in the parallel polarization direction (parallel to the pump light polarization direction) and the slope of the laser threshold curve (SER) in the vertical polarization direction (vertical to the pump light polarization direction) was used as the detection signal of the laser polarization of the acceptor. Findings indicate that as the K+ content in the DNA solution increases, the pumping threshold of the acceptor laser decreases, energy conversion efficiency improves, and the slope ratio of the acceptor laser reduces, leading to decreased polarization.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914005 (2024)
Process of Cleaning 45 Steel Rust Layer Based on COMSOL Kilowatt Laser
Le Yang, Lichuan Ning, Jinbo Liu, and Jintang Yang
By using COMSOL Multiphysics software to simulate a high-power mobile laser cleaning experimental platform with wavelength of 1064 nm, repetition rate of 20?100 kHz and power of 1000 W, visualized analysis of the laser cleaning process is carried out. The effects of the peak power density and cleaning speed on the changes of the temperature field and erosion morphology of the pollutant layer and substrate are investigated. To validate the findings, scanning electron microscope and roughness testers are utilized to study the laser cleaning effects under different peak power densities and overlapping ratios. The results show that with the increase of the laser cleaning time, the temperature variation during the laser cleaning process on the rust layer followed Gaussian distribution. The theoretical cleaning threshold and damage threshold for cleaning 45-grade steel found to be 1.9×107 W/cm2 and 10.0×107 W/cm2, respectively. Within these thresholds, the cleaning efficiency and the cleaning effect improved with an appropriate reduction of the cleaning speed as the peak power density increased. The best cleaning effect achieved with peak power density of 6.0×107 W/cm2, cleaning speed of 300 mm/s and corresponding overlap ratio of 70%. These findings are significant for enabling the industrial parameterization of kilowatt-level laser cleaning experiments. By using COMSOL Multiphysics software to simulate a high-power mobile laser cleaning experimental platform with wavelength of 1064 nm, repetition rate of 20?100 kHz and power of 1000 W, visualized analysis of the laser cleaning process is carried out. The effects of the peak power density and cleaning speed on the changes of the temperature field and erosion morphology of the pollutant layer and substrate are investigated. To validate the findings, scanning electron microscope and roughness testers are utilized to study the laser cleaning effects under different peak power densities and overlapping ratios. The results show that with the increase of the laser cleaning time, the temperature variation during the laser cleaning process on the rust layer followed Gaussian distribution. The theoretical cleaning threshold and damage threshold for cleaning 45-grade steel found to be 1.9×107 W/cm2 and 10.0×107 W/cm2, respectively. Within these thresholds, the cleaning efficiency and the cleaning effect improved with an appropriate reduction of the cleaning speed as the peak power density increased. The best cleaning effect achieved with peak power density of 6.0×107 W/cm2, cleaning speed of 300 mm/s and corresponding overlap ratio of 70%. These findings are significant for enabling the industrial parameterization of kilowatt-level laser cleaning experiments.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914004 (2024)
Numerical Simulation and Experimental Study of Nanosecond Pulse Laser Cleaning of DC04 Cold-Rolled Strip Surface Oil
Jiafan Hao, Wenbin Qin, Youqiang Liu, Menghua Jiang, Yinhua Cao, and Zhiyong Wang
According to the cleaning demand of cold rolled oil on DC04 cold rolled strip surface, we use COMSOL Multiphysics software to establish the temperature field distribution and oil stain removal process model of nanosecond pulse laser cleaning oil stain on DC04 cold rolled strip surface. The results show that when the spot radius is 80 μm and the laser energy density reaches 3.48 J/cm2, the oil can be basically removed. Then, a nanosecond pulsed laser is used to clean cold rolled oil on the surface of cold rolled strip steel. The results show that when the laser energy density exceeds 3.48 J/cm2 and the laser spot overlap rate is 50%, the oil pollution can be removed, which is consistent with the simulation results. In addition, the influence of laser spot overlap rate on laser cleaning effect is also studied. The results show that the laser energy density should be increased to 4.47 J/cm2 when the spot overlap rate is reduced to 37.5%. Therefore, nanosecond pulsed laser can effectively clean the cold rolled oil on the surface of DC04 cold rolled strip without causing obvious damage to the surface of the strip, which provides a reference for determining the process parameters of nanosecond pulsed laser to clean other kinds of materials. According to the cleaning demand of cold rolled oil on DC04 cold rolled strip surface, we use COMSOL Multiphysics software to establish the temperature field distribution and oil stain removal process model of nanosecond pulse laser cleaning oil stain on DC04 cold rolled strip surface. The results show that when the spot radius is 80 μm and the laser energy density reaches 3.48 J/cm2, the oil can be basically removed. Then, a nanosecond pulsed laser is used to clean cold rolled oil on the surface of cold rolled strip steel. The results show that when the laser energy density exceeds 3.48 J/cm2 and the laser spot overlap rate is 50%, the oil pollution can be removed, which is consistent with the simulation results. In addition, the influence of laser spot overlap rate on laser cleaning effect is also studied. The results show that the laser energy density should be increased to 4.47 J/cm2 when the spot overlap rate is reduced to 37.5%. Therefore, nanosecond pulsed laser can effectively clean the cold rolled oil on the surface of DC04 cold rolled strip without causing obvious damage to the surface of the strip, which provides a reference for determining the process parameters of nanosecond pulsed laser to clean other kinds of materials.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914003 (2024)
Exposure Time Optimization of Laser Interference Direct Writing Device Based on MEMS Micromirror
Guanqun Yu, Lü Baiying, Yue Xu, Zhongming Zeng, and Dongmin Wu
Laser interference direct writing device constructed with MEMS (microelectro mechanical systems) micromirrors has advantages such as small size, fast writing speed and simple optical path. However, it is necessary to adjust the exposure time to achieve uniform exposure effect during scanning. We introduce the optical path composition and control method of this type of laser interference direct writing device. The lookup table method is used to optimize the generated exposure pattern and exposure time parameters, reducing the pixel diameter variation from about 84% to about 6%. It solves the problem of uneven exposure time in the application of laser interference direct writing devices based on MEMS micromirrors. Laser interference direct writing device constructed with MEMS (microelectro mechanical systems) micromirrors has advantages such as small size, fast writing speed and simple optical path. However, it is necessary to adjust the exposure time to achieve uniform exposure effect during scanning. We introduce the optical path composition and control method of this type of laser interference direct writing device. The lookup table method is used to optimize the generated exposure pattern and exposure time parameters, reducing the pixel diameter variation from about 84% to about 6%. It solves the problem of uneven exposure time in the application of laser interference direct writing devices based on MEMS micromirrors.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0914002 (2024)
Topics
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20