Research Of Mid-infrared Pulsed Fiber Lasers Based On Mental-organic Frameworks

In recent years,mid-infrared pulsed fiber laser technology has made great progress due to the important applications in spectroscopy,surgery,communications and other fields.Compared with continuous wave(CW)or quasi CW lasers and ultrashort pulse lasers,lasers with short pulse duration scales of?s?ns have the important characteristics of high average power and high pulse energy.With the rapid development of passive Q-switching technology and new nanomaterials,mid-infrared pulsed fiber lasers based on new nanomaterials have been studied widely.Metal-organic frameworks(MOFs)have drawn considerable attention due to their unique properties and widespread applications.Great effort has been paid to explore the linear and nonlinear optical properties of MOFs such as remarkable second-harmonic generation intensity and multiphoton harvesting.However,the third-order nonlinear optical properties of MOFs and their applications as optical switches in the important mid-infrared region have rarely been studied.In this thesis,MIL-68(Al),MIL-68(Fe),MIL-101(Cr)and MIL-101(Cr)-NH₂ were prepared by hydrothermal synthesis and their morphological and nonlinear characteristics were studied.In addition,passively Q-switched fiber lasers based on them were studied.The main research works are summarized as follows:(1)Using MIL-68(Al)as a saturable absorber(SA),passively Q-switched fiber lasers based on Tm³⁺-doped fiber and Er³⁺ZBLAN fiber are realized,respectively.At the center wavelength of 1988.5 nm,an average output power of 3.08 m W at a repetition rate of 42.44 k Hz is recorded.At the center wavelength of 2793.6 nm,a pulse width of 546 ns and the maximum output power of 1.18 W is obtained.Watt-level pulse generation is achieved.(2)Using Tm³⁺-doped fiber as gain medium,passively Q-switched fiber laser based on MIL-68(Fe)is realized.At the center wavelength of 1973.3 nm,an average output power of 50.32 m W and a repetition rate of 50.32 k Hz are obtained.Passively Q-switched fiber laser based on Er³⁺ZBLAN and MIL-68(Fe)is realized,too.At the center wavelength of 2785.6 nm,an average output power of 581.62 m W and a pulse width of696 ns are achieved.(3)Using MIL-101(Cr)and MIL-101(Cr)-NH₂ as saturable absorbers,respectively,passively Q-switched fiber lasers based on Er³⁺ZBLAN fiber are realized.The generated pulses have the maximum average output power of?500 m W and the shortest pulse duration of?750 ns at the center wavelength of 2785.6 nm.The corresponding pulse energy and peak power are 2.72?J/2.27?J and 3.43 W/2.87 W,respectively.The experimental results show that the four MOFs materials(including MIL-68(Al),MIL-68(Fe),MIL-101(Cr)and MIL-101(Cr)-NH₂)have good saturable absorption properties in the mid-infrared band of?2?m and?3?m.They can be used as efficient optical switches to achieve high performance mid-infrared pulsed fiber lasers.