High Power Fiber Laser Based On Erbium-Doped ZBLAN Optical Fiber In Visible And 3?m Band

In recent years,high-power fiber laser with wavelengths of 3 ?m and visible light?especially 660 nm and 550 nm?have become a hot research field for researchers with their wide applications in biomedical,materials processing,and gas detection.In this paper,the high-power pulsed fiber laser with 3 ?m band and the switchable red-green fiber laser were studied from theory and experiment.The main research work can be divided into the following four points:1.Based on the study of ion transition theory,a passively Q-switched pulsed laser model based on Er³⁺-doped ZBLAN fiber in 3 ?m band was established by combining the rate equation,power transfer equation,and passive Q-switching in the time domain.The model was numerically solved and the effects of fiber length and fiber doping concentration on the threshold pump power and the output laser slope efficiency were studied.The effect of pump power on the repetition frequency and pulse width of the passive Q-switch pulse was also studied.The results of the research show that the optimal threshold pump power and slope efficiency can be obtained when the fiber length is 3.2 m and the doping concentration is 6-7.5 mol.%.With the increase of the pump power,the repetition frequency of the passively Q-switched pulsed laser increases linearly,while the pulse width shows a trend of decreasing firstly and then gradually tending to be gentle.2.Based on the simulation theory,passively Q-switched pulsed fiber lasers based on saturable absorption mirrors?SESAM?and Er³⁺-doped ZBLAN fiber was built.In the experiment,Er³⁺-doped ZBLAN fiber with a concentration of 7 mol.%and a length of 3.1m was used.The 976 nm semiconductor laser?LD?was used as a pump source and SESAM was used as a modulation device.At a pump power of 18.7 W,a passive Q-switch pulse with an average power of 3.01 W,a repetition rate of 278.5 kHz,a pulse width of 0.45 ?s,a pulse energy of 10.82 ?J,and a peak power of 24.45 W was obtained.The pulsed laser had a center wavelength of2798.8 nm,a full width at half maximum?FWHM?of 0.27 nm,and a slope efficiency of 17%.3.A passively Q-switched pulsed fiber laser based on Fe²⁺:ZnSe crystal and Er³⁺ZBLAN-doped fiber was constructed.In the experiment,7 mol.%Er³⁺-doped ZBLAN fiber was used as the gain fiber,and the fiber length was 2.75 m.At the same time,a double-ended pump structure was used.Both LDs had a wavelength of 976 nm.The Fe²⁺:ZnSe crystal was used as a modulation device.At a pump power of 16.2 W,a passive Q-switch pulse with average power of 3.51 W,repetition frequency of 369.3 kHz,pulse width of 0.274?s,pulse energy of 9.5 ?J,and peak power of 34.69 W was obtained.The pulsed laser had a center wavelength of 2822.3 nm,a FWHM of 0.26 nm,and a slope efficiency of 21.4%.4.The feasibility of switchable red-green fiber lasers was studied from the perspective of ion transitions.In the experiment,1.5 mol.%of Er³⁺-doped ZBLAN fiber was used as the gain fiber,and the fiber length was 15 m.At the same time,pump sources with wavelengths of 976 nm and 2 ?m were used to achieve an up-conversion green output with a central wavelength of 548.6 mm.After adding a 2 ?m pump source,an up-conversion red output with a central wavelength of 663.8 nm was obtained.The experiment also further validated the feasibility of switching red-green fiber lasers.