Characterization of mode-locked fiber lasers

Ultrafast lasers have applications that span many disciplines from materials science to medicine. Traditionally, ultrafast lasers are assembled from a Ti:Sapphire (T:S) gain medium due to a fast pulse duration (5fs) and high output power. However, a large drawback to T:S is the cost and size. An ultrafast fiber laser (FL) can be developed for a lower cost and take up less space. Drawbacks to a FL is low power output and long pulse duration (20fs). A goal in FL development is to match the performance of a T:S laser. Characterizing performance of these lasers involves measurement of output power, repetition rate, and pulse duration. The assembly of the laser requires splicing optical fiber from a pump diode to fiber of several optical components. The laser is then mode-locked. Mode-locking is the process of generating an ultrashort pulse in the laser cavity by introducing a component called a saturable absorber. Mode-locking is crucial to producing an ultrafast laser. The mode-locked power is 58.5mW and the repetition rate is 45.5MHz, offering a pulse energy of 1.26nJ. The pulse duration is measured with a technique called second-harmonic intensity autocorrelation. Autocorrelation is necessary as the pulse is too fast for electronics to respond. The pulse duration is 97.4fs.