Preparation And Mid-infrared Luminescence Of Chalcohalide Glass Ceramic Containing Perovskite Nanocrystals

3-5μm mid-infrared laser light sources are in the low-loss window of the atmosphere and covers the characteristic absorption spectrum of many important molecules.It has some applications in many cutting-edge photonics fields,such as infrared imaging,sensing,medical diagnosis,infrared countermeasures,etc.Therefore,it is of great significance for our national economy and national security to develop the laser in this band.Active ions doped chalcogenide glasses are considered as an ideal medium for mid infrared laser gain because of its low phonon energy(<425cm^-1),high refractive index and wide infrared transmission range.However,the chalcohalide glass has some disadvantages:（1）due to the weak chemical bonding in the glass,the mechanical properties and thermal shock resistance of the material are poor,and the material is very sensitive to crack propagation;（2）compared with the crystal,the rare earth ions in the glass material have non-uniform broadening,which leads to the low emission cross section and luminous efficiency of the material.In order to achieve high-efficiency mid infrared laser output,an ideal method is that a kind of composite material of chalcohalide phase and specific nanocrystalline phase is to obtained by glass thermal crystallization method,that is chalcohalide glass ceramic.The glass ceramic combines the advantages of crystal and glass material,which can have similar or even better optical properties of crystal,and has obvious advantages similar to glass material,such as simple preparation technology and low cost.Moreover,the mechanical,thermal and chemical properties of the material will be greatly improved.Based on this,the transparent chalcohalide glass ceramics containing CsPbI₃ perovskite nanocrystals were prepared by melt quenching method.The X-ray powder diffraction（XRD）,high-resolution electron microscopy（TEM）,Raman spectroscopy,infrared absorption spectroscopy,fluorescence spectroscopy and crystallization kinetics were used to systematically study the microstructure,crystallization mechanism and mid infrared luminescence of the materials.The main results are as follows（1）In the GeS₂-Sb₂S₃-CsI-PbI₂ glass system,a high transparent glass-ceramic containing CsPbI₃ perovskite nanocrystals was prepared.The XRD results showed that CsPbI₃ perovskite nanocrystals with cubic phase structure were precipitated in the glass matrix after the appropriate heat treatment.TEM results show that the glass melt has phase separation during the process of forming the precursor glass,and a large number of spherical I-rich regions with a size of～10nm are uniformly distributed in the glass matrix.During the heat treatment of glass samples,CsPbI₃ crystal nuclei will be formed at the phase-phase interface produced by the phase separation.As the heat treatment time increases,these crystal nuclei will grow into CsPbI₃ with a size of-20nm and uniform distribution by means of diffusion control.Thanks to this,the transmission range of the glass ceramics containing CsPbI₃ nanocrystals is 0.98-11.7μm,which is close to that of the precursor glass.（2）The Dy³⁺-doped transparent chalcohalide glass-ceramic containing CsPbI₃perovskite-nanocrystalline are prepared.The absorption spectrum results show that the glass-ceramic has strong absorption at 1320nm and can be used as the best light source for laser pumping.Fluorescence spectroscopy results show that the fluorescence of Dy³⁺-doped CsPbI₃ perovskite-containing nanocrystalline chalcohalide glass-ceramics at2.95μm and 4.40μm is significantly stronger than that of the precursor glass.The fluorescence lifetime results show that the fluorescence lifetimes corresponding to2.95μm and 4.40μm in the material have increased from 4.57ms and 0.91ms of the precursor glass to 5.55ms and 0.93ms of the glass-ceramics,which may indicate that some Dy³⁺ions may enter into the CsPbI₃ nanocrystals with low phonon energy,the mid-infrared luminescence is increased.（3）Ni²⁺-doped chalcohalide containing glass-ceramics CsPbI₃ perovskite nanocrystalline were prepared.The absorption spectrum results show that there is an obvious broad absorption peak at 2037 nm in the precursor glass.After appropriate heat treatment,the broad band absorption peak is obviously blue-shifted from 2037 nm to 1950nm.Fluorescence spectroscopy results show that Ni²⁺-doped chalcohalide glass ceramic shows a 2.5-5.4μm ultra-wideband mid-infrared fluorescence emission under a 1550nm pump source,which is expected to be a broadband tunable laser gain medium.（4）Ni²⁺doped chalcohalide glass-ceramic fiber containing CsPbI₃ nanocrystal was successfully drawn by rod-tube method.The transmission loss of the optical fiber measured by the truncation method,and the result show the loss located at 3.0μm and3.5μm is 18.9 d B/m and 18.1 d B/m,respectively.Although the fiber loss is relatively large,it provides a reference value for further reducing the loss of the mid-infrared fiber laser gain medium in the later period.