Preparation And Performance Of Thermal Stable Bismuth-doped Lanthanum Aluminum Barium Gallogermanate Glass And Fiber

Bismuth doped laser materials can luminesce in an extremely broad spectral range from 1000 to 1700 nm or even to 2000 nm, therefore, they are of crucial importance to develop new fiber lasers and optical amplifiers. Their potentials have been proved by the successful development of bismuth doped glass fibers and fiber lasers, nevertheless, so far there are still some crucial problems which need to be solved in this field. One of the problems is the nature of bismuth near infrared(NIR) luminescence. Another is that the current bismuth doped fibers have been achieved only with very low bismuth doping concentration and thus low gain efficiency. In order to develop the bismuth doped high-performance fiber laser and amplifier, these problems have to be resolved. In this paper, we are devoted to solve these key scientific problems and the results are as follows: 1. In order to study the bismuth near-infrared(NIR) luminescence mechanism, we prepared the Ba2B5O9Cl: Bi and Ca Al12O19: Bi crystals and found that the NIR emission centers can be generated in reducing atmosphere but disappear in oxidizing atmosphere. By means of in-situ reduction method, we can achieve the conversion continuously from Bi3+â†'Bi2+â†'Bi+â†'Bi0. Besides, bismuth doped crystals with NIR and red light emissions were prepared, and direct spectroscopic evidences were obtained which support the Bi+ and Bi0 as NIR emission centers. 2. Multi-component glasses are suitable for high concentration bismuth doping, however, while they are treated at glass softening point, phase separation and crystallization as well as fluorescence quenching will easily happen. In this work, we invented a bismuth doped lanthanum aluminum barium gallogermanate glass with high bismuth doping concentration and good thermostability. After optimizing the glass composition and melting process, we broke through the problem and finally prepared the bismuth doped germanate bulk glass. Moreover, thermal decay experiment of this glass indicated that there are 6% luminescence loss after the first heating and cooling cycle process but no obvious loss can be observed after more subsequent thermal cycle process. 3. By using the invented bismuth doped germanate glass and rod in tube technique, we manufactured the bismuth doped optical fiber with core and cladding diameters about 10 μm and 125 μm, respectively. Numerical aperture of this fiber is 0.3 and the transmission loss at the wavelength of 1310 nm is 9.05 d B/m. The luminescence of bismuth doped fiber is the same as the glass.