Design And Characteristic Research Of ZnO Random Laser

Random laser is a new type of microcavity laser which is proposed on the principle of the stimulated radiation. More and more scholars begin to study random laser due to its special luminous principle and optical properties. Different from the traditional laser, random laser doesn`t have optical resonator. The feedback in random laser may come from two possible mechanisms: one is the light is reflected back into the medium in the interface between air and disorderly medium. And then the feedback is formed. The other is a beam form a closed loop which is called circular cavity in the disordered medium. The circular cavity which is similar to the cavity plays a feedback role. Due to the distribution of scattered particles is random, the location of the annular cavity is random. The frequency, the direction and the intensity of the laser also have randomness. Compared with the oneness of traditional lasers, when the area of pump, the volume of random medium and the intensity of pump are changing, the spectrum graph, the model number and the output laser intensity will be also changed.Based on the light emission properties of random scattering particles and the light transporting properties of waveguide, the paper designs a new random laser, optimizes the structure parameters, study the coupling of light waves and analyze the radiation characteristics of random laser.In this paper the main contents of this thesis are as follows:First, this paper simply introduces the purpose and significance of studying random lasers, the characteristics of random laser, the research status of random laser. Then analysis the problem of the random laser research field for the design of the structure of the new type of random laser in this paper.Second, based on the principle and basic theory of random laser, we put forward and design a new random laser structure which is based on waveguide, Au and Zn O. The distribution of the optical filed and the modes spectra in the random laser system are numerically simulated by using the Finite Difference Time Domain(FDTD) method. We also compare and analyze the optical field and the modes spectra of random laser while using Au particles and Au film, respectively. The results show that the number of modes which have better monochromaticity will be reduced with the existence of Au particles player, and using Au film can increase the output laser intensity.Finally, the paper put forward a new type of zinc oxide random laser with two circular flaws which are symmetrical. The zinc oxide particles are randomly distributed. The distribution of the optical filed and the spectrogram of mode in two-dimensional random scattering particles system are numerically simulated and compared by using the finite difference time domain method, when D which is the distance between the two symmetrical circular flaws changes. The dependence of the emission intensity and the center wavelength on D is analyzed and we obtained that the optimal parameters are the best while D=0.8μm. In ideal conditions, the optical field distribution of scattering system is observed during the simulation process. The result shows that the electric field intensity between two circular flaws is amplified after coupling. With the increasing of D which is the distance between the circular regions, the electric field intensity is enhanced, the spectral line width is decreased, and the number of modes is reduced.