Laser Cooling Of The Yb³⁺-doped Fluoride Crystal

Laser cooling of solids is becoming more attractive for both fundamental physical scientists and applied physical scientists due to it has tremendous charming physical phenomenon and extremely important application in the area of aerospace, remote sensing and telemetry, photoelectric detection, high power laser and so on. This dissertation main study laser cooling of Yb3+-doped fluoride crystal in theory and in experiment.We adopted four energy level model describe the process of laser cooling of the rare earth doped system. According to this model, we obtained the relationship the cooling efficiency with external quantum efficiency, absorption efficiency, mean fluorescence wavelength, and pump wavelength. The heat loads of the sample come from three parts:blackbody radiative load, air convective heat load, supporting conductive heat load. We analyzed the effect of heat load from these three different sources and give the solution to reduce the heat load correspondingly.Cooling micron or nano scale detector is the new challenge for us. We propose two new conceptions which are Surface Plasmon Resonant enhancement laser cooling of solids (SPRELCS) and resonant waveguide structure coherent enhancement laser cooling of solids (RWCELCS) for cooling the micro or nano scale detectors. Firstly, we deduced the relationship the enhancement factor with the position of film and obtained the express of the mean enhancement factor. Secondly, we adopted the10wt%Yb3+:YLiF4film as our model in the theory, and calculated the enhancement factor function in the film with the different thickness of the film. Finally, we calculate relationship the final temperature of10wt%Yb3+:YLiF4film with the power of the pumping laser. While the process of the calculation, we taken account of the saturate power intensity.We adopt the resonant external cavity enhancement absorption experiment study the laser cooling of2wt%Yb3+:YLiF4crystal. Firstly, we measured the relationship the mean fluorescence wavelength with temperature. And then, we obtained the temperature calibration curve of the sample with DLT method. After that, we lock the length of the cavity on the wavelength of the pump laser. On hour later, the sample reached the state of thermal balance with environment, and then we recorded the DLT single of sample. Compared with the temperature calibration curve in early, we can deduce the final temperature of the sample. Utilizing the four energy level model, we can obtain the cooling power, cooling efficiency and background absorption. According to these results, we can draw the cooling window of2wt%Yb3+:YLiF4crystal by which we can comprehensive understanding of the properties of laser cooling of this crystal. Finally, we compared our experiment results with the results of LANL and University of New Mexico research group directly.We adopt the resonant external cavity enhancement absorption experiment study the laser cooling of2wt%Yb3+:LuLiF4crystal. Firstly, we analyzed the demands for Yb3+-doped fluoride materials cooled down to cryogenics temperature by laser in theory. And obtained some Yb3+-doped fluoride crystal as potential candidates who can be cooled down to cryogenics temperature by laser. And then, we measured the relationship the mean fluorescence wavelength with temperature. We also obtained the temperature calibration curve of the sample with DLT method. After that, we lock the length of the cavity on the wavelength of the pump laser. On hour later, the sample reached the state of thermal balance with environment, and then we recorded the DLT single of sample. Compared with the temperature calibration curve in early, we can deduce the final temperature of the sample. Utilizing the four energy level model, we can obtain the cooling power, cooling efficiency and background absorption. According to these results, we can draw the cooling window of2wt%Yb3+:LuLiF4crystal by which we can comprehensive understanding of the properties of laser cooling of this crystal. Finally, we compared the potential of cooling ability of both the Yb3+:LuLiF4crystal and the Yb3+:YLiF4crystal and the advantages for the crystal growth and the practical application between them. And we found out both of them there is the same promising potential for laser cooling to cryogenics temperature.