Rectangular Pulse Passively Mode-locked Thulium Doped Fiber Laser

Fiber laser has the characteristics of simple structure,good heat dissipation effect and controllable performance,which is widely used in optical communication,sensor,laser processing,medical and other fields.In recent years,the fiber laser working in the safety area of human eye about 2.0 ?m has shown many unique advantages,and has been widely concerned in many application fields.Thulium doped fiber(TDF)has a wide range of emission wavelength from 1.8 ?m to 2.1 ?m,which is considered to be an ideal gain medium for 2 ?m band fiber lasers.In this thesis,the dissipative soliton resonance pulse and rectangular pulse thulium-doped fiber laser are studied.In addition,based on the saturable absorption effect of low dimensional semiconductor nanometer materials,the passively mode locked thulium-doped fiber laser is realized.The main research contents are as follows:1?Research of wavelength-spacing adjustable dual-wavelength dissipative soliton resonance thulium-doped fiber laser.Using the equivalent saturation absorption effect of nonlinear fiber loop mirror as the passively mode-locking mechanism,the generation of dual-wavelength dissipative soliton resonance pulses in thulium-doped fiber laser is realized based on birefringent Lyot filter composed of a polarizer and a polarization-maintaining fiber.Moreover,due to the inherent tunability of the online birefringent Lyot filter,the dual-wavelength spectra can be tuned by adjusting the polarization controller,and the wavelength interval is basically unchanged.It is also found that tunable single-wavelength pulses with switchable wavelength can also be generated at the two central wavelengths of thedouble-wavelength pulse.2?Study on square wave pulse passively mode locked thulium doped fiber laser with adjustable pulse duration and amplitude.The generation of noise-like square wave pulses from thulium-doped fiber lasers is realized by using the equivalent saturation absorption effect of nonlinear amplifying ring mirror as passively mode-locking mechanism.In this structure,there are two pumps,one of which can be used to adjust the amplitude of the square pulse and the other to adjust the width of the square pulse.The experiments show that the pulse duration and amplitude of the square wave pulse can be adjusted independently and continuously.3 ? Study on passively mode-locked thulium doped fiber laser based on titanium nitride nanoparticles saturable absorber.Based on the saturable absorption effect of titanium nitride nanoparticles,a stable mode-locked pulse laser is obtained in thulium-doped fiber laser.The results show that titanium nitride nanoparticles can be used as saturable absorbers in thulium doped fiber lasers,which will be helpful to further explore the application of metal nitride nanoparticles structure in mid infrared photon devices.