The New Rare-earth Laser Materials

As the basic elements, laser materials have significant importance for the development of laser and laser technology. Since a laser system was first demonstrated in 1960, laser technologies had been widely applied in various fields and served for the humanity. In the past decades, rapid development of modern science and technology declared the coming of the Third Industrial Revolution. Laser and its technology are promoting fast development of the optical telecommunication industries with power and energy. In order to realize the strategy of being a worldwide powerful country with advanced manufacturing and information industry in the 21st century, the most important thing is to supply the great demands on laser materials and components. Novel materials bring up novel devices. Due to some technical problems and inherent limitations of conventional lasers, much work has been devoted to studying on novel materials in order to obtain ideal lasers. Therefore, to explore and develop novel laser materials is not only the basic step of fabricating high efficient lasers and laser systems for future, but also has great potential application value and significant meaning.The main subject of this thesis focused on developing novel laser media. After reviewing the developing status of laser materials home and abroad and analyzing the merits and faults of the existing technology routes, we produced some kinds of novel rare-earth doped laser media. Technical requirements and technology routes of the new systems have been researched theoretically and experimentally. Important progresses have been made, which lays the foundation for new lasers.Main contents of the thesis are summarized as follows:1. In order to resolve the bottleneck issues to the further development of the erbium-doped heavy metal oxide glasses which suffering from low quantum efficiency due to serious excited state absorption, we successfully developed a novel erbium-doped bismuth-based glass system. The excited state absorption and up-conversion of erbium were restrained, emission intensity was enhanced and novel amplifiers with broadband and good properties were made.2. A novel tetranuclear neodymium complex was synthesized and the structure was characterized. Laser media were prepared by dissolving the complex into organic media such as polytrifluorochloroethylene oil, PMMA. Optical properties such as absorption spectrum, photoluminescence spectrum and fluorescent lifetime were investigated. Compared with some other Nd³⁺ complexes where all the protons of the ligands are either deuterated or fluorinated, these materials showed outstanding properties. The stimulated emission cross-section in PMMA was 2.55×10^-20 cm², which was comparable to the value of 1.35×10^-20 cm² from the well known host LaF3: Nd. With these advantages, this material has potential applications in the ongoing search for low-cost and low power rare-earth doped organic lasers.3. Explore novel liquid laser materials in two ways: Nd³⁺ dissolved in organic solutions and micro-balls dispersed into organic solutions. Tetranuclear neodymium complex was dissolved in DMF with high concentration, forming a liquid laser medium with uniformity, transparency, stability and low toxicity. The stimulated emission cross-section was 3.13×10^-20cm². Fluorescent Resonance Energy Transfer theory was applied to investigate the quenching mechanism of the liquid sample. In order to decrease the influence of C-H and O-H bonds, novel fluorinated complex (C₂F₅COO)₃Nd(Phen) was prepared and dissolved in DMSO-d₆ to form liquid laser medium. Compared with some other Nd³⁺ liquid materials reported previously, fluorescent lifetime and quantum efficiency were improved effectively. Besides, the concept of "flowing solid" lasing material was first brought forward and novel liquid laser material was obtained by dispersing neodymium phosphate glass micro-balls into specific organic liquids. Optical characterization and theoretical analysis demonstrated that this novel material had excellent laser optical properties. The fluorescence lifetime was 300μs and the stimulated emission cross section was 3.0×10^-20 cm², showing that it is quite suited for being used as a high-energy laser medium.4. Technical requirements of liquid solvents for novel liquid lasers were investigated in detail. Solvents with good properties such as DMSO-d₆ and MMAF were selected. According to the spectrum properties, pumping conditions were designed and the probabilities as laser materials were analyzed and evaluated. For the micro-ball dispersion system, the serious influences of scattering loss were overcome by applying specific organic liquid to get the refractive index suitably matched. In the laser experiment, laser output was successfully achieved and laser output characteristic was further studied. This is the first time that a neodymium liquid laser might be truly put into practical application.