1.5 μm被动调Q可饱和吸收体用Co:MgAl_(2)O_(4)透明陶瓷的制备

Fabrication of Highly Transparent Co:MgAl_(2)O_(4) Ceramic Saturable Absorber for Passive Q-switching at 1.5μm

钴掺杂的镁铝尖晶石透明陶瓷是用于近红外区域工作的无源调Q固态激光器的有效材料。为制备具有高吸收截面和高透过率的Co:MgAl_(2)O_(4)透明陶瓷,采用共沉淀法合成钴掺杂的纯相镁铝尖晶石纳米粉体,并通过真空烧结结合热等静压烧结(Hot Isostatic Pressing,HIP),制备得到了高质量的0.05at%Co:MgAl_(2)O_(4)透明陶瓷,同时系统研究了预烧结温度对Co:MgAl_(2)O_(4)陶瓷微观结构和光学性能的影响。当预烧结温度从1500℃升高至1650℃,Co:MgAl_(2)O_(4)陶瓷的相对密度从95.2%增大到98.5%,而当预烧温度升高至1700℃,Co:MgAl_(2)O_(4)陶瓷的相对密度降低至97.7%。真空预烧后Co:MgAl_(2)O_(4)陶瓷的相对密度较低,因此预烧后的Co:MgAl_(2)O_(4)陶瓷均为不透明的。当预烧温度从1500℃升高到1700℃,Co:MgAl_(2)O_(4)陶瓷的平均晶粒尺寸从2.3μm增大到11.3μm。经过HIP后处理后,在1550~1700℃×5 h真空预烧条件下的Co:MgAl_(2)O_(4)陶瓷都是透明的,而经过1650℃×5 h真空预烧结合1800℃×3 h HIP后处理的Co:MgAl_(2)O_(4)透明陶瓷表现出最佳的光学质量,在400和900 nm处的直线透过率分别为81.4%和85.9%,平均晶粒尺寸为16.8μm。在500~700 nm和1200~1600 nm波长范围内的宽吸收带表明Co2+已掺入尖晶石晶格中。此外,经计算,最佳光学质量的样品在1540 nm处的基态吸收截面为6.18×10^(-19)cm^(2),表明Co:MgAl_(2)O_(4)已经成为固态激光器中被动调Q可饱和吸收体的最有潜力的材料之一。

The cobalt doped magnesium aluminum spinel is an efficient material for the passive Q-switching solid state lasers operating at the near infrared region.In order to prepare Co:MgAl_(2)O_(4) transparent ceramics with high absorption cross section and high in-line transmittance,the cobalt doped magnesium aluminum spinel nanopowders with pure phase were synthesized via the co-precipitation method.And after vacuum sintering and hot isostatic pressing(HIP),highly transparent 0.05at%Co:MgAl_(2)O_(4) ceramics were obtained.The influences of pre-sintering temperature on morphology and optical property of the Co:MgAl_(2)O_(4) ceramics were studied.With the pre-sintering temperature increasing from 1500-1650℃,the relative density increased from 95.2%to 98.5%,while the relative density decreased to 97.7%with the pre-sintering temperature increasing to 1700℃.Because of the relative low density,the Co:MgAl_(2)O_(4) ceramics were all opaque after vacuum pre-sintering.In the sintering temperature range of 1500-1700℃,the average grain size increased from 2.3 to 11.3μm.After HIP post-treatment,the Co:MgAl_(2)O_(4) ceramics pre-sintered from 1550 to 1700℃were all transparent,the Co:MgAl_(2)O_(4) ceramics pre-sintered at 1650℃for 5 h and HIP post-treated at 1800℃for 3 h showed the best optical quality,which were 81.4%at 400 nm and 85.9%at 900 nm,and the average grain size was 16.8μm.The broad absorption bands in the wavelength range of 500-700 nm and 1200-1600 nm indicated that Co2+had incorporated into the spinel lattice.Moreover,the ground state absorption cross section of the best specimen is calculated with a value of 6.18×10^(-19) cm^(2) at 1540 nm,meaning that it’s a promising candidate for passive Q-switching in solid-state lasers.