Study Of Ytterbium Doped Optical Microcavity

The microsphere cavity with whispering gallery modes (WGM) can confine optical power into a tiny volume for a long time and almost free from dissipation, thus the microsphere cavity posses the characteristics of ultrahigh quality factor (Q) and small modal volumes. Moreover, microsphere cavities can induce intense coupling between cavity electromagnetic modes and substances, thereby have attracted a lot of attention in basic physics research field and the application of low threshold laser research field. This paper studied luminescence properties of the Yb3+doped microsphere cavity.The preparation of rare earth ions doped silica microsphere cavity requires acquisition of bulk samples of rare earth doped glasses that are manufactured into microsphere structure afterwards. This article has described a versatile method for preparation of the rare earth ions doped silica microsphere cavity, which was the sol-gel method. The original silica microspheres served as a basic resonator, and the gain functionalization of the surface was performed by rare earth ions doped sol-gel films. Preparation of the sol-gel solution and fabrication of the rare earth ions doped silica microsphere cavity are described specifically in this paper. The optical fiber taper is a good coupler for both coupling pump laser into microspheres and extracting light emission from them with high coupling efficiency which can be as high as 99%. We have employed fiber-taper-coupled microsphere system to investigate the rare earth ions doped silica microsphere cavity.Firstly, this article studied cooperative luminescence in an Yb3+doped silica microsphere, under the excitation of 976 nm laser, blue emission (with 20 nm blue shift) was observed in an Yb3+ doped silica microsphere, which was generated by cooperative luminescence of excited Yb3+ ion-pairs and the absorption of phonons, and the process was explained by an energy level diagram. In addition, the high energy density of pump laser near the surface of microsphere enables the creation of saturation effect. Subsequently, this article studied the down-conversion laser of the Yb3+ doped silica microsphere, under the excitation of 976 nm laser, low threshold down-conversion laser was observed in an Yb3+ doped silica microsphere, which will operate more efficiently in a water environment compared with a 1.55 μm laser. Thirdly, this article introduced the nonlinear effect of the Yb3+ doped silica microsphere, under the excitation of 976 nm laser, a self-stimulated cascaded Raman laser was observed, which was stimulated by the down-conversion laser of the Yb3+doped silica microsphere. The self-stimulated cascaded Raman laser locates in the zero dispersion point of optical fiber, and may be a promising candidate for amplification of the signal transmitted at 1.3μm.On the other hand, this article studied luminescence properties of the Yb3+-Eu3+ codoped microsphere cavity. Firstly, cooperative energy transfer in Yb3+-Eu3+codoped microsphere cavity. Under the excitation of 976 nm laser, cooperative luminescence of excited Yb3+ ion-pairs and luminescence of Eu3+ were observed. The mechanism corresponding to the observed up-conversion of Eu3+ was cooperative energy transfer from Yb3+ ion pairs to Eu3+. Subsequently, this article introduced the nonlinear effect of Yb3+- Eu3+ codoped microsphere cavity, under the excitation of 976 nm laser, a self-stimulated cascaded Raman laser was observed in Yb3+-Eu3+ codoped microsphere cavity.