3. Time scales: from continuous to femtoseconds

3.1 Continuous operation

Continuous wave operation is the default mode of a single laser cavity, although sometimes spontaneous phase locking or triggering phenomena are observed. If no effort is made to control the spectrum of the laser emission, this continuous emission consists of several longitudinal modes in the spectral domain, whose frequencies satisfy the equation (5) . This property is due to the partially inhomogeneous nature of gain broadening in doped optical fibers. The number of modes oscillating in the laser cavity can be reduced by introducing an optical filter. If, in addition, the...