Study On Propagation Properties Of Elegant Gaussian Beams Through Left-handed Material

Different from conventional medium,the Left-handed medium created a new field for the development of physics.A lot of strange phenomena will appear when electromagnetic wave passes through Left-handed medium,such as negative refraction effect,reverse Doppler effect and so on.In recent years,the applications of the Left-handed medium have obtained more and more attention in the fields of optics,materials science and electromagnetic.Therefore,it is important to research the propagation properties of the beam through the Left-handed material(LHM).In this thesis,we mainly study propagation properties of elegant cosh-squared-Gaussian beams(EchSGB)and sinh-squared-Gaussian beams(ShSGB)through a Slab LHM.Based on the generalized Huygens-Fresnel diffraction integral,the propagation expressions of three-dimensional intensity for EchSGB and ShSGB in free space,in slab LHM and after propergating through the slab LHM are derived;The analytical expressions of the spot size,2M-factor,waist width and position of the EchSGB and ShSGB are deduced by the second-order moment method.Then the numerical calculations and analysis are performed to explore propagation properties of the EchSGB and ShSGB through the slab LHM.The results show that:1.The beam waist width of EchSGB only depends on the parameters of a and b,which are associated with the elegant cosh-squared-factor.The beam width,the waist location and the2M-factor not only depend on the parameters of a and b,but also related to the negative refractive index.The negative refractive index of the LHM will change the distribution position of the beam,the parameters of a and b will change the shape and size of the beam.When we choose a certain paticular value of the negative refractive index,the EchSGB could reappear under the influence of the left-handed materials.Therefore,in practical applications,choosing the EchSGB with smaller parameter values through the LHM with a larger negative refractive index,the betterquality beams are obtained.At the same time,it is feasible to shape beams in the manner of adjusting the beam parameters and the negative refractive indexes at different locations.2.The influence of the LHM on the axial and the transversal intensity distribution of ShSGB leads to the intensity exhibit symmetrical distribution.The negative refractive index of the slab LHM will change the position of the maximum intensity.The axial and transversal intensity will be changed with different transmission distances and parameter of a,which is associated with the sinh-squared-factor.The beam width just depends on parametera.The axial and transversal intensity,the beam width,the waist location and the2M-factor not only depend on the parameter a,but also with a negative refractive index.The smaller parameter a and the greater absolute value of negative refractive index can cause a smaller2M-factor,in other words,the beam quality is better.In addition,it is feasible to shape ShSGB in the manner of adjusting the beam parameters and the negative refractive indexes at different locations.