Optical modulation of microfibers and application to ultrafast fiber lasers

Microfibers with different waist diameters were prepared successfully by a flame-brushing technique. Their saturable absorption properties were investigated. The non-saturable loss and modulation depth both decreased with the increase of the diameter. According to the mode distribution of microfibers with a waist diameter of 25 mu m, it could be supposed that the evanescent field effect may be useful for microfibers being saturable absorbers (SAs). Based on the 25 mu m-diameter microfiber, an all-fiber-structure mode-locked fiber laser was achieved successfully with long term stability in the span of a week. The results indicated that microfibers with suitable diameters were excellent SAs. To the best of our knowledge, this is first report on the usage of microfibers as a SA for building ultrafast fiber lasers.