Research On Mid-Infrared Laser Characteristics Of Er:Y₂O₃ Ceramics

Solid-state lasers are widely used in military,medicine,communications,environment and many other fields because of their important role.With the development of solid-state lasers,the wave bands of solid-state lasers have been covered from visable and near-infared bands to ultraviolet and mid-infrared bands.3μm wave bands laser have very strong water absorption and high damage threshold to biological tissues,so it has very important application prospects in gas monitoring and medical treatment.At present,the generation of 3(im solid-state laser is mainly based on Er3+ doped gain media pumped by LD whose center wavelength is around 980nm,such as Er3+:YAG,Er3+:CaF2,Er3+:Y2O3 and so on.Oxygen ceramics have been extensively studied due to their high melting temperature,mechanical hardness,chemical stability and low phonon energy.The CW and Q-switching characteristics of 3μm Er3+:Y2O3 solid-state laser are studied in this paper.Firstly,the important applications and development of 3μm band laser were introduced,and the different ways of producing 3μm band laser doped with rare earth ions were described.The mechanism and mode of producing energy level transition of Er3+ doped solid laser are emphatically introduced.Then,the mechanism of Q-switching,saturable absorption characteristics and passive Q-switching rate equation theory were introduced.The absorption and emission spectra were analyzed and the corresponding spectral parameters are calculated.At the same time,the intensity parameters are calculated by J-O theory.Next,we designed and optimized the film-systems required for the laser experiment based on the analysis of the absorption and emission spectral characteristics.Laser experiments with Er3+:Y2O3 ceramics doped concentration of 7at%were done.The CW output with wavelength of 2716.3nm,maximum output power of 780mW,slope efficiency of 11.8%was achieved.Finally,laser Q-switched experiment were carried out.At the begin,Laser self-Q-switching were realized with wavelength of 2717.0nm,maximum output power of 106mW,pulse width of 1.39us and arepetition frequency of 26.7kHz.Then,single and three layers of graphene were prepared by chemical vapor deposition method.They were transferred to substrate of CaF2 glasses and then inserted into laser resonator for passively Q-switched experiment.The laser with wavelength of 2717.0nm,output powers of 0.14W and 0.11W was obtained.Respectively,laser slope efficiencies were 3.1%and 1.4%,and the narrowest pulse width,maximum repetition frequency,maximum pulse energy and the peak power were(408ns、51.1kHz、2.58μJ、6,35W)and(296ns、44.2kHz,2.59μJ、8.77W).Then,passively Q-switched experiments were carried out by a few layers of WS2.We obtained maximum output power of 233.5mW at 2716.3nm,with laser slope efficiency of 10.6%,and the narrowest pulse width,the maximum repetition frequency,the maximum pulse energy and the maximum peak power were(720ns,29.4 kHz,7.92J,11.0W).