Third-order Nonlinear Optical Properties Of Transparent Chalcogenide Glass Ceramics Based On Ge-Sn(Ga)-S

Since the 21^stcentury,with the further development of optical fiber communication technology,mankind has gradually entered the era of high-speed information.Relevant research areas,such as optical computing,optical storage,and all-optical communication networks,have been developed rapidly.Meanwhile,the demand for high-performance photonic devices has also been increasing.Therefore,the well-known passive devices such as all-optical switches,optical filters,and wavelength converters exhibit an unprecedented huge market.For these applications,the material should have high nonlinear optical property.Among these materials,chalcogenide glasses（Ch Gs）have high nonlinear refractive index n₂,which is more than 100 times that of quartz glass,excellent infrared transparency（up to 25μm）and high thermal stability.More importantly,chalcogenide glasses can be easily formed into form films and fibers,thus are promising for infrared nonlinear photonic devices.The main purpose of this paper is to explore the third-order optical nonlinear properties of chalcogenide glass-ceramics based on Ge-Sn（Ga）-S system,and to evaluate their applicability to nonlinear photonic devices.Firstly,we investigated innovative research of Ge-Ga-S chalcogenide glasses.Although this glass system have been extensively studied,there are also few systematic studies on the third-order optical nonlinearity properties of the Ge-Ga-S glass-ceramics.Therefore,we chose halides as the nucleating agent,and studied the third-order nonlinear optical properties of Ge-Ga-S glasses and glass-ceramics that are transparent in the entire visible light band range after doping with high halides;secondly,we take Ge-Sn-S,a relatively novel ternary system chalcogenide glass body,and use Au as its nucleating agent.The third-order optical nonlinearity of Ge-Sn-S glass-ceramics after microcrystallization was studied.We found that the unsaturated Sn²⁺ions in Ge-Sn-S glass can reduce the introduced Au,and thus grow Au nanoparticles in the glass matrix.When the particle size is relatively small,the third-order optical nonlinear characteristics of Ge-Sn-S chalcogenide glass have been greatly improved.Therefore,the main content of this article is divided into the following three points:（1）Study on the third-order optical nonlinearity of highly halide-doped Ge-Ga-S chalcogenide glass-ceramics that are transparent in all visible light bands.According to the previous reports on the third-order nonlinear studies of Ge-Ga-S chalcogenide glasses,we introduced two nucleating agents（CsCl and CsI）,and focus on the study of fully visible transparent25Ge S₂-30Ga₂S₃-45CsCl,chalcogenide glass and glass-ceramics（basic absorption edge is located at～370nm,slightly higher than the human eye’s 380nm visible edge）.The crystallites precipitated in the glass-ceramics are Ga₂S₃nanocrystals.Due to the size-limiting effect of the local crystal field,the sign and size of the nonlinear refractive index n₂of the glass at 800nm are changed.The maximum n₂value of glass-ceramics is 1.96×10^-18m²/W,which is four times that of matrix glass.（2）Study on the micro-morphology and optical properties of Au-doped Ge-Sn-S system chalcogenide glasses.On the basis of the 20Ge-5Sn-75S glass,we doped with 0.1mol%,0.2mol%,0.4mol%,0.7mol%,1mol%and other percentages of elemental Au,and thus a series of Au-doped20Ge-5Sn-75S glasses were obtained.By analyzing transmission electron microscopy photos,we found that Au nanoparticles have precipitated in the doped glass.The short-wave cut-off edge of Au-doped glass is obviously red-shifted,indicating the presence of surface tail band absorption on Au nanoparticles.The test results of the fluorescence spectra of doped and undoped Au glasses show that both glasses have a photoluminescence signal at a wavelength of～450nm,which belongs to the characteristic luminescence of Sn²⁺ions,indicating that the Au nanoparticles in the glass is related to the interaction of Sn²⁺ions.In addition,the Vickers hardness of the Au nanoparticle chalcogenide glass is 3.4%higher than that of the host glass without Au doping.（3）Study on the third-order optical nonlinearity of heat-treated Au-doped Ge-Sn-S chalcogenide glasses.On the basis of Au-doped 20Ge-5Sn-75S glass,we selected two heating temperatures（338℃and 368℃）and heat-treated the glasses at these two temperatures for 10hours.We found that Au nanoparticles showed stronger optical activity after heat treatment.Z-scan measurement results at 800 nm show shows that the 0.4mol%Au-doped 20Ge-5Sn-75S glass has the highest n₂value after heat treatment,up to 1.65×10^-16m²/W,which is three times that of Ge-Sn-S matrix glass without Au doping,and 100 times that of 25Ge S₂-30Ga₂S₃-45CsCl glass ceramics.In addition,the precipitation of more Au particles after heat treatment significantly reduced the characteristic luminescence of Sn²⁺ions at～450nm.