Research On Photoinduced Scattering Based Random Lasing Action And Weak Localization Of Light

With advancing of optics and photonics, the extremely important value of scattering in optical media, traditionally seen as annoyance, has begun to be realized in practice applications, scattering in gain media related researches has been one of the hottest topics. When photons propagated in the scattering gain media, multiple scattering of light occurred, and with the help of stimulated emission and intensity feedback, lasers would be formed. This kind of lasers was called random lasers since the output mode and direction of which were random. Random lasers do not need the feedback of resonant cavity, which have many advantages compared with traditional lasers, such as smaller volume, lower cost, and higher resolution when used in imaging and display, which was a complementation with the traditional lasers to develop the lasers related applications. Therefore, research on random lasers in scattering media has become one of the hottest research field. In this thesis, multiple scattering and random walks of photons were investigated in neodymium doped phosphate glass and lead lanthanum zirconate titanate ceramics based on photoinduced and electroinduced scattering aiming at achieving the localization of light and tunable random lasing action in the media. To realize multifunctional and tunable random lasers and optical amplifiers, the relationship between localization of light and random lasing actions have been discussed both experimentally and theoretically.Firstly, random lasing action and weak localization of light in highly transparent neodymium doped phosphate glass under normal light illumination was studied. Combining the photoinduced scattering effect in phosphate glass with light diffusion theory in scattering medium, theoretical analysis was given on random lasing and localization of light in the phosphate glass medium. Utilizing multiple scattering and incoherent feedback of light, upconverted random lasing action in the sample has been achieved, and lasing mode and random oscillation behavior has been analyzed. Based on the localization of light picture, weak localization of light and incoherent feedback interaction has been discussed.Based on the above work, to enhance the scattering intensity and study the tunability, random lasing action and weak localization of light were discussed in neodymium doped lanthanum lead zirconate titanate ceramics since more doping concentration is possible in ceramics. Based on photoinduced scattering property and light propagation theory, the changing of light scattering intensity L/lt, and transport mean free path lt along with pumping light intensity were discussed, and transmittance and reflection, resident time and absorption enhancement of light were analyzed. After the realization of upconversion random lasing in the sample, random lasing output intensity, slopes and thresholds were tuned with the change of the absorptive enhancement in different doping concentrations of neodymium ions.Ultilizing the electroinduced scatterers of ferroelectric PLZT ceramics, random lasing behavior was studied and modulated upon exposure to the corona atmosphere. Based on the changes of scattering intensity and enhanced absorption, multimode upconversion random lasing output intensity was modulated. Using the shortlived photoinduced scattering by a pulse laser, the radiation transition from spontaneous emission to stimulated emission was observed and investigated, and shortlived random lasing oscillation was obtained.To prove ubiquity of realizing random lasing acion with other rare-earth(RE) ions dopants, we expanded our investigation into other RE3+ doped PLZT ceramics. The relationship between absorption enhancement and scattering intensity was studied upon exposing to the corona atmosphere. Based on this relationship, the upconversion emission intensity in Er3+/Yb3+ doped PLZT ceramics was modulated. Stimulated amplification of seed light at different wavelengths in Er3+ doped PLZT ceramics was obtained upon exposure to the corona plasma atmosphere. The difference between different seed light in stimulated amplification process was analyzed and simulated by the absorption and stimulated emission cross section of the sample.