The study on the produced length of whispering-gallery-mode fiber laser

Abstract

Long length of whispering-gallery-mode fiber lasing emission along a fiber's axis is obtained by using the method of evanescence-wave optically pumped and gain coupled fiber laser. The relationship between produced length of lasing emission and pumping energy has been investigated. With the increasing of pumping energy, it is found from our experiment that the length of whispering-gallery-mode lasing emission along the fiber's axis is increased sharply, when the pumping energy is just larger than the threshold energy. However, the increasing trend of the produced length is slow when the pumping energy is much larger than the threshold energy. It was also found from the experiment that both dye concentration and refractive index of cladding gain solution have key affects on the produced length. Based on the characteristic of frustrated totally internal reflection of light traveling along the fiber, and the theory of evanescence-wave pumped and gain coupled fiber laser, an equation determining the produced length of lasing emission has been deduced, the calculated result with the equation matches the experimental data very well.