| With the invention of laser, solar pump laser has emerged to utilize solar energy and overcome energy crisis. Solar pump fiber laser has attracted much attention due to it’s excellent characters, such as small volume, good optical quality and so on. In the previous investigations, the most gain materials of fiber lasers were rear earth ions doped glasses. Owing to weak crystal field of glass, the non-radiation transition probability was high, and the absorption spectra exhibit narrow-line feature when rear earth ions doped into glasses. Thus, the conversion efficiency of solar by fiber was low. Glass ceramic is a material with high transmittance as well as strong crystal field, and it is easy to be processed into other shapes. Owing to the strong crystal field of glass ceramic, enhanced fluorescence were detected when the active ions doped in it. Besides, the absorption spectra of some active ions may present as broadband by regulating the crystal field of glass ceramic. Therefore, the utilization efficiency of solar by glass ceramics may be higher, glass ceramic will be a potential matrix for solar pump fiber laser. In this work,firstly, we intended to prepare transparent glass ceramic to convert visible sunlight into near-infrared emission. Then, we intended to prepare glass ceramic fiber to convert visible sunlight into near-infrared emission, which may lay a foundation for the preparation of sunlight pumped fiber laser.In this work, we have also performed a lot of exploratory experiments on the fabrication of glass ceramic fibers. We have proposed a novel method, which was called melt-in-tube method. The glass ceramic fibers fabricated by melt-in-tube method were crystallization controllable and can be used to convert visible sunlight into near-infrared emission. Furthermore, we prepared other fibers and glass ceramic fibers to verify the adoption of melt-in-tube method. The melt-in-tube method exhibits excellent applicability andwill open a new way for fabricating functional glass ceramic fibers. Detailed research contents and results are as follows:(1) The Ce3+/Cr3+-Yb3+ codoped precursor glasses were prepared by melt-quenching technique. After heat treatment, YAG nanocrystals were precipitated in the glass ceramics. The fluorescence spectra and lifetime curves were measured, it was noticed that there existed energy transfer process from Ce3+/Cr3+ to Yb3+ in Ce3+/Cr3+-Yb3+codoped glass ceramics. It was proved that the energy transfer from Ce3+ to Yb3+ was a single-photon process by comparing the absorption spectrum with excitation spectrum and measuring the emission spectra under different excitations. The energy transfer from Cr3+ to Yb3+was proved to be a single-photon multi-phonon assisted process by the emission spectra under different excitations and temperatures. Excited by visible solar simulator, enhanced near-infrared emissions were both detected in Ce3+/Cr3+-Yb3+ codoped glass ceramics compared to that in the precursor glasses. What’s more, the spectral conversion efficiency of Cr3+-Yb3+ codoped glass ceramic was higher than that of Ce3+-Yb3+ codoped.(2) The PbS doped borate glass was prepared by melt-quenching technique. After heat treatment,PbS nanocrystals were precipitated in the glass ceramic. The absorption and emission spectra of glass and glass ceramic were measured. It was observed that the glass ceramic exhibitted high transmittance in near-infrared region. Excited by 450 nm light, enhanced near-infrared broadband emissions were detected in glass ceramic compared to that in glass.The red-shift and broadening of emission spectra were observed with the heat treatment temperature increasing. Monitoring at 1100 nm emission, broadband excitation spectrum was detected in glass ceramic, which covered the whole visible region. Excited by visible solar simulator, enhanced near-infrared broadband emissions were detected in glass ceramicscompared to that in precursor glass. The red-shift and broadening of emission spectra were observed with the heat treatment temperature increasing. The spectral conversion efficiency of this PbS doped glass ceramic was comparable to that of Cr3+-Yb3+ codoped YAG glass ceramic.YAG glass ceramic exhibits high heat treatment temperature and severe light scattering.It is difficult to be processed into fiber. We chose PbS doped borate glass as fiber core to prepare glass ceramic fiber. The fiber clad was a K9 optical glass tube. The clad glass was softened while the core glass was melted at the fiber drawing temperature. By quick drawing, the precursor fiber was prepared. Then, the precursor fiber was heat treated in low temperature to obtain glass ceramic fiber.The EPMA images, Raman spectra and TEM images of fibers were measured. No crystallization or elements diffusion between fiber core and clad was observed in the precursor fiber. After heat treatment,PbS nanocrystals were precipitated within fiber core. Compared to the rod-in-tube method, melt-in-tube method was crystallization controllable; it can avoid the uncontrollable crystallization during fiber drawing process. Excited by visible solar simulator, enhanced near-infrared broadband emission were detected in glass ceramic fiber compared to that in precursor fiber.The red-shift and broadening of emission spectra were observed with the heat treatment temperature or time increasing.(3)The multi-component glass rods were drawn near the soften temperature. After drawing process, crystallizations appeared in glasses and the glasses turned to opaque. Rod-in-tube method was not suitable for fabricating glass ceramic fibers. Cr3+:ZnAl2O4, Ni2+:LiGa5O8 and Ba2TiSi2O8 glass ceramic fibers were prepared by melt-in-tube method, the fiber clad were silica glass tubes and the core were silicate glasses.The EPMA images, Raman spectra and TEM images of fibers were measured. No crystallization or element diffusion between fiber core and clad was detected in the precursor fiber. After heat treatment,Cr3+:ZnAl2O4, Ni2+:LiGa5O8 and Ba2TiSi2O8 nanocrystals were precipitated within fiber core. Excited by the corresponding lasers, enhanced emissions were detected in the glass ceramic fibers compared to that in precursor fibers.Melt-in-tube method is suitable for fabricating different functional glass ceramic fibers.(4) The multi-component bismuth doped glass rods were drawn near the soften temperature. It is hardly to avoid the precipitation of bismuth metal during the drawing process. After drawing process, the glass was opaque and the fluorescence was weaker. Rod-in-tube method was not suitable for fabricating bismuth doped multi-component fiber.We prepared bismuth doped multi-component fiber by the melt-in-tube method. The fiber clad was silica glass tube and the core was bismuth doped multi-component glass. The EPMA images and emission spectra of fiber were measured. The fiber was obtained without precipitation of bismuth metal. Excited by 808 nm laser, ultra-broadband near-infrared emission was detected in the fiber. Melt-in-tube method is suitable for fabricating bismuth doped multi-component fibers.
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