Research On All Solid-state Pulsed Laser Based On SESAM And Graphene Oxide Saturable Absorber

All-solid-state pulsed laser has the advantages of simple structure,diverse excitation wavelength,good beam quality and high pulse energy.It has a very broad application in the national defense,precision processing,medical and scientific research and other fields.The techniques of pulse laser generation mainly include Q-switching and mode-locking technology.SESAM is one of the most mature and widely used passive mode-locking devices,Research about SESAM is well developed abroad while it is still at an elementary stage in our country.However,the SESAM has a complicated manufacturing process and high price.In recent years,some two dimensional nano materials were found to have saturable absorption mechanism and was prepared into saturation absorbers,including carbon nanotube(CNT),graphene and graphene oxide(GO),topological isolator(TI),transition metal sulfides(TMD),black phosphate(BP),etc.These new saturation absorbers have been successfully applied to generate ultrashort pulse lasers in both solid state and fiber laser.Due to the advantages such as wide absorption band,fast response time,convenient and simple preparation,and low price,these new absorber materials have become a research hotspot recently.However,with the instability of most nano materials themselves,the damage threshold of the novel broadband saturable absorption device is Iow,and the immature preparation process also makes large insertion loss,which hindered the application of the novel nano materials absorber in the high-power solid-state pulsed laser.Based on the above background,in this thesis,the foreign brand SESAM,home-made SESAM and the prepared graphene oxide saturable absorber were all been used as a modulator in solid state laser.The main work of the paper includes:1.Based on the deep analysis of the principle of q-switching and mode-locking,a parameter which could indicate the similarity between the actual spot size and expected spot size of the critical position of the laser cavity is created creatively.Then,with the aid of MATLAB,the parameter is used to design the laser cavity with excellent thermal stability and super huge stable region,and another significant characteristic of the cavity is that the fundamental-mode spot size on the position of SESAM is extremely stable in the most stable region of the cavity.2.All solid state mode-locked Nd:YVO4 laser with foreign brand SESAM and home-made SESAM was realized in the same cavity which was designed by the above method.The maximum output power is 9.1 W and 5.7 W with a repetition rate of 108.28 MHz,The corresponding slope efficiency is 31.7%and 28%,respectively.3.A reflective saturable absorber based on graphene oxide was prepared by liquid phase stripping method and langmuir-blodgett(LB)technology on a reflective silver mirror.The parameters,such as reflectivity,scanning electron microscope(SEM)image,Raman spectra and modulation depth of the saturable absorber are measured,then the reflective saturable absorber was used to the solid-state laser,a maximum Q-switched mode-locked output power of 3.2 W with the slope efficiency of 31%was obtained.