The Theory Study On Optical Properties And Modulating Of Lasing In Random Media

In this dissertation, around the optical properties and the application of random laser, many problems about random media are studied, such as photon-localization, the spatial distributions of optical field, spectrum characteristics, modes competition and modulating for the radiation characteristics of random media by photonic crystals. A new scheme for fabricating flexible semiconductor microlasers is put forward, and this scheme can provide a new way to manufacture cheap micro-lasers with low threshold, good workability and possibility of being imbedded in optical integrated circuit.As the theoretical basis of this dissertation, the theory and algorithm of transfer matrix method (TMM) and finite difference time domain (FDTD) method are analyzed in detail, and a new holistic scattering effect physical model is put forward based on the experimental phenomena of random laser.Based on the holistic scattering effect physical model, the distributions of localized modes in 1D random media are simulated, and the relationship between random lasing emission and pumping area is analyzed. The results are coincident with experimental phenomena qualitatively and can explain some experimental phenomena of random laser reasonablely.A series of optical properties of 2D random media are studied and the results show that the light is localized obviously in the random media. And the spatial distribution of the energy is both related with positions of the particles and the wavelength of excitation light. The degree of localization is related with the particle filling density also, and if the particle filling density increases, the localization should become stronger. So the threshold should become lower. The emission spectra of random media take on the characteristic of spontaneous emission and the intensity of spectra is weak, so a pure random medium needs higher threshold.Some quasi-closed structures formed from the particles in random medium, different spectrums appear in different quasi-closed structures. When the wavelength of excitation light is not suited with the configuration parameter of a quasi-closed structure, the spectral peaks are changed with time frequently and the energy of the peaks is attenuated quickly. And when the wavelength of the light is more suited with configuration parameter of the quasi-closed structure, there is a certain peak keeping its leading status in its spectrums and the energy attenuates slowly. So photon-localization is both related with configuration of medium and the wavelength of excitation light and random laser can be regard as whole scattering effect between the medium and the excited light.To control the radiation characteristic of random laser, photonic crystal (PC) is introduced to forbid the spontaneous emission and lead it to the needing frequency. The radiation characteristic of the system combining random medium and PC is investigated. The results show that when the cluster was introduced into a perfect PC, some spontaneous emission spectral peaks drop off gradually and a new spectral peak emerged and then got the run upon rapidly. So if a random gain system could be put into a ordered system, the light energy could be confined in this system, spontaneous emission can be forbidden, the lasing modes could be modulated, the effective gain could be improved and the lasing threshold could be reduced effectively. Furthermore, the influences on modulating effect by structure parameters of PCs such as shape, size of crystal lattice particles, lattice type and dielectric constant are investigated in this dissertation.According to these results, an easier and cheaper scheme is put forward to manufacture flexible semiconductor microlasers, and the radiation characteristics of this kind of laser are simulated. The results show the flexible semiconductor microlaser has good optical property.