Mechanism Of Charge Carriers In Conducting Polymers Fission And Random Laser

This paper consists with two topics, involving carrier fission in polymeric molecule and the mechanism of random laser.Traditionally, polymers represent a key field of the chemical industry. However, in recent years, polymers have also become significant for physics in regard to both fundamental studies and applications. On the one hand, the discoveries of electroluminescence and photovoltaics have provided new possibilities for optoelectronic applications. On the other hand, due to its chain structure, the polymer is an excellent material for testing theories and models based on a onedimensional system. Earlier research on polymers has concentrated on ground-state and transport properties. Recently, many novel phenomena and applications based on excited states and dynamical process have been explored. Thanks especially to substantial progress in femtosecond laser spectroscopy, it is possible to reveal the details of various photoinduced dynamical processes in polymers. In this thesis, we study the structural change of the carrier induced by photoexcitation in polymers. Our dynamical simulation shows some special photoinduced processes whereby the carriers insimulation shows some special photoinduced processes whereby the carriers in polymeric molecule is split into two carriers. One positive bipolaron can be slipt into two positive polaron, and one positive polaron can be split into one a negative polaron and the other a positive bipolaron—where this photoinduced carrier fission does not need the aid of an external electric field, which is a typical symmetry breaking. In condensed matter physics, according to two degrees of freedom describing the properties of carriers, carriers can be divided into two categories: charge carriers and spin carriers. In inorganic materials, their carriers are electron and hole that both possess their spin and charge. Yet, the carrier in organic material is a composite particle that, different from inorganic material, are characterized with the surrounding lattice configuration. Thereby, besides the charged spin polaron that is similar to the electron or hole in organic material, there also exist spinless charged carrier, such as bipolaron. Because polaron is a spin carrier, combining with the polaron fission, we also developed a new dual principle of ESR (electron spin resonance), charge flipping of spin carrier.In 1968, the pioneer work of Lethokov predicted that laser action could be realized in randomly distributed scattering media. In the 1980s, Markushev et al. observed lasing in Nd-doped laser crystal powder. They found a single particle, with size much larger than the optical wavelength, served as a laser resonator. Since then, there has been much work on powder lasers. In 1994, Lawandy [4] applied 530nm laser pulse to pump the colloidal solution consisting of TiO2 particles suspended in Rodanmine methanol solution. Once the gain approached and surpassed the threshold value, laser action could be observed over the surface of the liquid, which triggered many experimental and theoretical studies on this field. The term "random laser" appeared. In order to realize laser with resonant feedback in random solid media,: Cao et al. [6] switched to a solid luminescence semiconductor. When the pump beam (the fourth harmonic X =266nm Nd: YAG laser) is focused on the ZnO polycrystalline thin film surface and its intensity exceeds a threshold value, narrow discrete sharp peaks emerges in the emission spectrum, and simultaneously, a couple of bright...