Nonlinear Optical Response Properties Of Er:YAG Ceramics

Er:YAG ceramics have good physical,chemical and mechanical properties.According to the different Er3+ ion doping concentration,the transparent ceramics can emit laser around 1.6 ?m band or 2.94 ?m band,which have important potential applications in optical communications,remote sensing,biomedical applications and other fields.At present,Er:YAG ceramics as gain media have been widely used in high power/high energy laser devices with different operating wave lengths.With the ever-increasing application of the output power requirements,the optical response characteristics of Er:YAG will present a non-linear feature.With the increase in power/energy,the appearance of the self-focusing effect will limit the final power boost of the Er:YAG solid laser and it will eventually affect the performance of the laser device or cause material damage.At present,the third order nonlinear optical properties of Er:YAG have not been reported.How to extract the nonlinear optical parameters of Er:YAG ceramic materials will provide a reference for Er:YAG performance improvement and high power laser applications.In this thesis,we studied the nonlinear optical response of Er:YAG ceramics by nonlinear Z-scan method,and measured the nonlinear optical response characteristics of Er:YAG ceramics at 800 nm and 1560 nm,respectively.We obtained the nonlinear absorption properties and the nonlinear refractive index.The main research results of this thesis include:(1)We built and optimized the ultra-fast Z-scan test platform and used the carbon disulfide to calibrate the 800 nm Z-scan experimental system.Through the experimental data fitting,we obtained the third-order nonlinear refractive index of carbon disulfide is about 2.85×10-19 m2/W.The data are consistent with the values of the existing references,demonstrating the reliability of our experimental test platform.The ITO glass was measured using a 1560 nm Z-scan experimental system,and we obtained the third-order nonlinear refractive index of it is about 2.3x10-16 m2/W.Similar to the values reported in the existing references,the experimental results also proved the accuracy of the test platform.(2)Based on the Z-scan method,the nonlinear optical response parameters of the Er:YAG ceramics at 800 nm were obtained,and the influence of the doping concentration on the nonlinear optical response was obtained.The nonlinear optical properties of Er:YAG ceramics with 0.5%,1%and 5%doping concentrations were measured.We observed that the open aperture data of the samples with different doping concentrations have obvious and similar reverse saturation absorption characteristics,and the closed aperture data have self-focusing effect.We used MATLAB software to fit the experimental curve and calculated the third-order nonlinear refractive index values of the Er:YAG ceramics to be on the order of 10-21 m2/W.(3)The nonlinear optical parameters of the Er:YAG ceramics at 1560 nm and their variation were obtained.Experimental results show that the different doping concentrations of Er:YAG ceramics have significant reverse absorption characteristics and self-focusing effect.By fitting the Z-scan nonlinear transmittance curve,the third-order nonlinear refractive index values of the Er:YAG ceramics are calculated on the order of 10-17 m2/W.At the same time,the different physical mechanisms of the nonlinear properties of Er:YAG ceramics were analyzed.