Photonics studies: Rare-earth chromophores for polymer optical amplifiers.

摘要

In this thesis, we report the results of our photonics studies, both theoretical and experimental, of rare earth chromophore-doped polymer systems. Further, we demonstrate that these rare earth-doped polymers are promising candidates for photonics applications, such as optical fiber and waveguide amplifiers and lasers.; The rare earth-doped polymers we have developed are qualitatively different from previously studied inorganic glass and crystal systems. The main distinction is that in polymer systems, rare earth ions are first encapsulated by insulating, covalently-bonded, organic ligands before being incorporated into the polymer host, whereas bare ions are doped directly into inorganic glass and crystal hosts. Moreover, these active chromophores have marked controllable effects on the optical and material properties of rare earth-doped polymers.; Rare earth ions such as {dollar}rm Ersp{lcub}3+{rcub}, Ndsp{lcub}3+{rcub}, Smsp{lcub}3+{rcub}, Eusp{lcub}3+{rcub}, Prsp{lcub}3+{rcub}, Tbsp{lcub}3+{rcub}{dollar} are encapsulated as various rare earth chromophores and evaluated in many organic and polymer hosts. We measure metastable state lifetimes, absorption and emission cross-sections, and implement Judd-Ofelt analyses to obtain radiative and nonradiative transition rates. We also determine optimal doping concentrations by studying concentration quenching of the metastable state lifetime and concentration-dependent dissociation effects. Finally, once the optical properties and the optimal doping concentrations are found, we numerically simulate the performance of the corresponding rare earth-doped polymer optical fiber amplifiers.; We have analyzed many different rare earth chromophore-doped systems. One promising candidate for amplification at 650 nm is Sm(HFA){dollar}rmsb4NEtsb4{dollar} in PMMA-d{dollar}sb8.{dollar} The metastable state lifetime and emission cross-section for this system are found to be 194 {dollar}mu s{dollar} and {dollar}4.5times10sp{lcub}-21{rcub} cmsp2,{dollar} respectively, and doping concentrations can approach 10 wt%. For fiber diameters of a few microns, lengths of around 10 centimeters, and optimized doping concentrations, optical gains for this system are calculated to be several to 10 dB. These gains reflect a two orders of magnitude improvement achieved through chromophore design in this study, with only one more order of magnitude necessary to reach commercially practical optical gains. To this end, work is underway to develop fully-fluorinated and other heavy-atom polymer systems that would eliminate nonradiative decay and, hence, provide increased efficiencies. Additionally, current research group efforts are focused on building rare earth-doped polymer devices and studying amplification.