Passively Q-switch Laser Performance Of Several Two-dimensional Nano Materials

In recent years,graphene as the representative of the two-dimensional nano material has become the focus of attention of researchers.Nanomaterials have different from bulk material in optical,electrical and magnetic properties.With the advantages of wide absorption wavelength,short response time and low optical loss,the two dimensional nanomaterials exhibit excellent saturable absorption properties in optics field,which has broad application prospects in the field of laser modulation.Doping can change the structure and properties of two-dimensional nanomaterials.At present,most of studies focus on preparation and characterization of the doped materials whose saturable absorption performance is involved less.In the second and the last chapter of this thesis,the nitrogen doped graphene and the carbon doped boron nitride were selected as the research object,and the stable output of the 1064 nm passively Q-switch laser was achieved.The experimental results show that doping can play an important role in the saturable absorption properties of two-dimensional nanomaterials.In the fourth chapter,two tungsten sulfide and molybdenum disulfide as the research object,were applied to Nd:GdVO4 in all solid state laser.The results show that the dimension of two dimensional nanomaterials has some influence on the passively Q-switch modulation.The main research contents and results are as follows:(1)Research on the structure of the nitrogen doped graphene.By means of atomic force microscopy,Raman spectroscopy and X ray photoelectron spectroscopy,it was confirmed that the nitrogen atoms have entered into the graphene lattice and the material structure was complete.Nitrogen doped graphene can be used as saturable absorber for all solid state lasers.(2)The output characteristics of passively Q-switch laser with nitrogen doped graphene were studied.The results of passively Q-switch pulse were 61 mW,284 kHz,103 ns,0.21 J,2.08 W,separately.The experimental results of pure graphene as a reference object were obtained at 56 mW,510 ns,105 kHz,0.11 J,1.05 W.Under the same experimental conditions,the nitrogen doped graphene as Q-switching element,the output pulse sequence was more orderly,narrower width and better modulation effect,which proves that the saturated absorption performance of nitrogen doped graphene was better than that of pure graphene.(3)The structure of boron carbon nitrogen was studied.Scanning electron microscopy and atomic force microscopy were used to observe the morphology of boron carbon nitride.According to the results of X ray diffraction,it was concluded that the carbon atoms had been embedded into the hexagonal boron nitride nanosheets.(4)The nonlinear absorption properties of boron carbon nitride films were studied.The results showed that the boron carbon nitride films exhibited the saturable absorption properties at low incident light intensity,and reverse saturable absorption properties at high incident light intensity.The samples with different carbon content exhibited different nonlinear optical absorption properties,so the nonlinear absorption coefficient can be changed by adjusting the concentration of carbon atoms.(5)The output characteristics of passively Q-switch of boron carbon nitride films were studied,hexagonal boron nitride as a reference.The experimental results of the passively Q-switch modulation of boron carbon nitride nanosheets and hexagonal boron nitride nanosheets were obtained by inserting them into the 1064 nm laser cavity:the maximum output power of 24 mW,18 mW;repetition rate were 537 kHz,730 kHz;the narrow pulse width were 121.8 ns,136 ns;the maximum pulse energy was 0.045 J,0.025 J;the peak power was 0.367 W,0.184 W.These data indicate that the absorption properties of boron carbon nitride nanosheets are better than those of the six boron nitride nanosheets.(6)Passively Q-switch output characteristics of two tungsten disulfide and molybdenum disulfide were studied.According to the results of the atomic force microscope,different sizes materials were nunbered,and modulated the Nd:GdVO4 solid state continuous laser.The optimal passively Q-switch results was showed with 6 nm thick two tungsten sulfide:the pump power was 615 mW,the maximum output power of 106 mW was obtained,corresponding to the repetition frequency of 973 kHz,pulse width of 26 ns,pulse energy of 0.11 J,peak power of 4.19 W.The passively Q-switch effect with 9nm thick molybdenum disulfide was secondly.The experimental results show that the thickness of 2D material is an important factor to affect the passively Q-switch effect.