Study On Stimulated Emission From Polymer Film

The demonstration of stimulated emission in conjugated polymers makes these materials promising as high gain media for solid-state lasers. Some of the unique properties that make conjugated polymers attractive candidates for such applications are their high photoluminescence quantum efficiency , large stimulated emission cross-section,tuneable emission wavelength, simplicity of fabrication and low cost. In thesis,the work is concentrated on study of the stimulated emission characteristics in MEH-PPV film. Moreover,the factors that influence the stimulated emission are investigated.Stimulated emission is demonstrated from MEH-PPV films formed by spin coating. The change of the emission spectra detected from the edge of the sample showed a clear threshold and a gain narrowing emission peak when increasing the excitation intensity. The spectral location of the emission peak can be slightly tuned by altering the slab waveguide thickness to control the allowed propagating modes in waveguide.With increasing thethickness of the polymer film,the threshold of stimulated emission diminishes and the gain increases.A maximum gain of 25.03cm^-1 and a minimum threshold of 2.2uJ/pulse are obtained at the thickness of 150nm. In addition, the influence of substrates is also investigated. We found that using polymer substrates can make the parameters of stimulated emission become worse. It can be concluded that result from two factors. First,it is not easy to form waveguide on the polymer substrates duo to their high refractive index.Meanwhile,it can lead to additional optical loses for the large roughness of polymers. Our results indicate that MEH-PPV are an attractive gain medium in optically pumped polymer lasers.