Fabrication and analysis optical microsphere cavity based on high Q erbium-doped

Using CO₂ laser metal method process the top of erbium-doped tapered fiber, which formed by stretching a standard optical fiber (SMF-125) while heating it with a hydrogen flame. The top of tapered fiber formed erbium-doped microsphere cavity with higher spherical by its surface tension when heating is stopped. The size of erbium-doped microsphere is 21μm. The position of erbium-doped microsphere is accurately adjusted between the pump power and monochromatic spectrometer so that it can be easily excited by 980 nm and 1480 nm infrared light. Excited erbium ions produce energy level transition and a number of sharp transmission spectrums are observed around the center wavelength of 1550nm. It expanded the spectrum wide and proved the frequency selection role of micro-cavity. Further analysis of the experimental results, we obtained the quality factor Q=4.4×10⁸ through calculating the transmission spectrum which is consistent with the theoretical value largely.