| Tellurite glasses have been widely studied from bulk materials to structured devices, with the emphasis on the development of nonlinear optical fibers to demonstrate the functionalities of supercontinuum generation, erbium doped fiber amplifier and Raman amplifiers, etc. The new type tellurite-based optical fibers exhibit superior advantages over conventional silica ones, due to their high optical nonlinearity, broad transmission window, high rare earth element solubility and Raman gain intensity. Like silica fibers, tellurite fibers may also incorporate various fiber structures including solid core-cladding one and microstructure one (e.g. photonic crystal). The fiber loss was ever reported as low as ∼1dB/m using rod-in-tube fabrication process.;Beyond all those progresses, little success has been made on improving the optical nonlinear property of tellurite glasses chi(3) ∼ 50 times bigger than fused silica). The challenge remains for tellurite glasses that their optical nonlinearity is more than 1 order smaller to compare with chalcogenides, although they are more stable chemically and structurally. In this work, after carefully reviewing the trend of optical nonlinearity for solid glasses, we adopted two strategies to potentially increase the linear and third-order optical nonlinear properties for tellurite glasses. A more polarizable electronic excitation may be achievable by introducing chalcogen elements (e.g. Sulfur or Selenium) into TeO2 vitreous network and synthesizing glasses with a linear helical chainlike structure. The ab initio computational results of microscopic hyper-polarizabilities of hypothetical mixed - 2 - tellurite chalcogenide glass molecular structure (TeO2(TeOX)n) confirmed the enhanced effect as Te-X (X=S or Se) bonds exist and the molecular size (n) grows. Quantitative estimates of the macroscopic linear and nonlinear properties for a mixed glass made from chains of n = 5 units leads to a conclusion that the extra Te-S (or Te-Se) bonds in the mixed tellurite-chalcogenide system will enhance the linear refractive index n0 and the third-order susceptibility chi(3) by factors of ∼1.3 (or 1.4) and ∼8 (or 14) respectively, over the base tellurite glasses (X = O). As the chalcogen replacement is kept under 50%, the main TeO2 vitreous network within the mixed glasses is not going to be altered so that a good chemical stability is maintained. Therefore, the proposed new type tellurite glasses mixed with chalcogen atoms may promise better performance of nonlinear optical fibers in the realization of white light source and optical amplification. |
