报告题目：Cooling effect on fluoride crystals
报告人：Prof. Mauro Tonelli
主持人：印建平教授
时间：2017.11.29 上午10:00
地点：理科大楼A814
报告人简介：
Prof. Mauro Tonelli is the coordinator of the research group “New Materials for Laser Applications” operating at the Physics Department of Pisa University. He is the famous for laser crystal growth and application, especially for alkali halides crystals, oxide and fluoride crystals doped with rare earth ions. The growth facility of his research group has been developed inside the Physics Department of Pisa University and it is the only one in Italy and one of the few in the world to develop insulator fluoride materials for medical, mechanical and laser applications, especially for the solid state crycooler by optical pumping. He is also working in the Virgo gravitational interferometer on optical detection systems to detect gravitational waves. He is co-author of more 300 papers published on refereed books and scientific journals. And the paper was cited more than 10538 times.
报告内容简介：
We have investigated the cooling effect on insulator materials by optical pumping. In particular we evaluated the critical cooling parameters: ab and EQE (ηext) of different crystals. We studied LiYF4 crystals doped with different Yb3+ doping levels. Moreover, it has been estimated the cooling power for possible optical crycooler applications. On the same materials (LiYF4) we proposed a new possible scheme to increase the cooling efficiency. This has been possible co-doping the samples by Yb3+ and Tm3+.
In these experimental conditions, we obtained an interesting effect on cooling parameters: the decrease of the ab, the increase of EQE and the red shift of the peak wavelength. To understand these effects, it has been studied the absorption and emission spectroscopy. In particular we studied the emission of the manifolds of Tm3+ (1G4 and 3H4) and the energy transfer mechanisms between Yb-Tm to investigate the variation of cooling parameters. This approach has allowed to obtain the lowest temperature (87 K) and the highest ∆T=190 K. Other materials have been studied as LiLuF4 doped with Yb3+ and it has been evaluated the ab and ηext. In particular it has been investigated a disorder crystal (KYF4) doped with Yb3+and showed for the first time the cooling effect.