We demonstrate a novel (to the best of our knowledge) whispering-gallery-mode fiber laser, pumped and gain coupled by evanescent waves, by inserting a bare optical fiber into a glass capillary filled with dye solution. The energy threshold properties of the lasers, including the energy threshold that varied with the refractive index (RI) of the dye solution for different fiber diameters and the produced length of the lasing emission along the fiber axis, are then investigated. We find experimentally that the energy threshold is very sensitive to the RI of the dye solution and the fiber diameter, and the produced length of the lasing emission is dependent on the dye concentration and the RI of the dye solution. The optical gain of a circular microcavity in the evanescent-wave pumping scheme is analyzed by introducing a Gaussian distribution function of the pump light, and various energy losses related to the microcavity are considered, which leads to a threshold energy formula. The formula for determining the produced length of the lasing emission is derived by introducing an attenuated factor in the threshold energy formula. The experimental results are in good agreement with the calculations.
© 2011 Optical Society of America
Lasers and Laser Optics
Original Manuscript: May 5, 2011
Revised Manuscript: June 23, 2011
Manuscript Accepted: June 28, 2011
Published: July 29, 2011
Yuan-Xian Zhang, Xiao-Yun Pu, Kun Zhu, and Li Feng, "Threshold property of whispering-gallery-mode fiber lasers pumped by evanescent waves," J. Opt. Soc. Am. B 28, 2048-2056 (2011)