Study On Damage Characteristics Of Femtosecond Laser On Chalcogenide Glass And Fiber End Face

Chalcogenide glasses have attracted extensive attention due to their unique optical properties,including ultrabroad infrared transmission range,ultrahigh linear and nonlinear refractive index.These excellent optical properties enable chalcogenide glass fibers to have broad application prospects in various fields,such as mid-infrared laser delivery,supercontinuum spectra generation and Raman fiber laser.In such applications,chalcogenide glass and end face of chalcogenide fibers frequently interacts with laser pulses.However,ultrashort pulsed laser possesses extremely short pulse width and high peak energy,which makes irreversible damage on the surface of glass or fibers occur easily.Firstly,the paper briefly summarizes the advantages and application prospects of chalcogenide glass and optical fiber,introduces the characteristics of femtosecond laser and the corresponding processing application,and then summarizes the research progress and current status of the interaction between ultrashort pulse laser and optical materials.Then the damage mechanism on optical materials interacted by the femtosecond laser is introduced,including self-focusing effect,thermal effect and defect-induced damage.Based on the wide application prospects of chalcogenide materials under the irradiation of ultrashort pulse laser,the investigation of femtosecond laser damage characteristics on chalcogenide glass and fiber materials are put forward.In this paper,the damage properties of Ge-Sb-Se glass samples,As2S3 glass and the end face of As2S3 fibers by femtosecond laser were studied.The series glass samples of Ge11.5Sbx Se88.5-x(x=5,10,15,20,25,30)were fabricated using the conventional melt-quench method.The purified As2S3 glass was prepared by multiple distillation method,and the remaining As2S3 preform was drawn into fibers with uniform diameter.The damage characteristics of Ge-Sb-Se glasses,As2S3 glass and fiber end face under femtosecond pulse laser were explored through self-built damage experimental platforms,including correlations among structure,water peak absorption and femtosecond damage characteristics of Ge-Sb-Se chalcogenide glasses and femtosecond laser-induced damage on the end face of As2S3 glass fiber at the wavelength of 800 nm in comparison with the bulk As2S3 glass.The main innovations of the research include:(1)As the Sb content increases from 5 mol% to 30 mol%,the optical band gap of Ge-Sb-Se glass samples decreases from 1.70 e V to 1.24 e V,the hardness increases from 98.16 kg·mm-2 to 135.12 kg·mm-2,the average bond energy increases,whereas the laser damage threshold at 4 μm wavelength decreases from 201.42 m J/cm2 to 121.87 m J/cm2,in which the photoionization process dominates in the femtosecond laser damage on chalcogenide glass.Meanwhile,the water absorption peak wavelength corresponds to a low laser damage threshold.Ge-Sb-Se glass samples irradiated with femtosecond laser at the wavelengths of 2.86 μm and 4 μm,the self-focusing critical powers were reduced from 0.0685 μW to 0.0052 μW,from 0.1352 μW to 0.0104 μW,respectively;(2)Compared the femtosecond laser-induced damage on As2S3 glass at 800 nm with that in the mid-infrared,the damage threshold is smaller at 800 nm,which is mainly related to the photoionization process and the heat accumulation;(3)The damage characteristics on the end face of commercial As2S3 fiber with 800 nm femtosecond laser pulse show that fiber with lower transmission loss corresponds to a strong resistance for the femtosecond laser damage(laser damage threshold is about 61.42 m J/cm2).The results of this study can provide scientific reference for the design of novel photonic devices based on Ch G glass fibers in the future.