Self-starting ultrafast fiber lasers mode-locked with alcohol

We report a novel saturable absorber (SA) based on anhydrous alcohol for mode-locked fiber lasers (MLFLs). The SA is an optical ferrule with one alcoholic end-facet sealed by a polyethylene (PE) film. Its modulation depth is measured to be 5.9%. Also, a self-starting MLFL using such an alcohol-SA has been demonstrated to generate 972-fs pulses at 1594.6 nm. The single pulse energy is up to 1.8 nJ with the repetition rate of 20.97 MHz, and the signal-to-noise ratio (SNR) is higher than 50 dB. The MLFL exhibits the performance of self-starting, good stability, and high pulse energy. Such a cost-effective and easily-prepared SA with high damage threshold may find wide applications for ultrafast lasers. Besides, it may arouse wide considerations of the mode-locking function of organic liquids for ultrafast lasers.