The fabrication and performance of a colliding pulse mode locked laser with an intracavity saturable absorber is described. The laser has a threshold current of 65 mA and differential efficiency of 0.04 mW/mA when coupled into a single mode fiber. Mode locked pulses with similar to 1 ps pulse width at similar to 10 GHz has been obtained.

A theory of small signal frequency response of four-wave mixing (FWM) in a traveling wave semiconductor optical amplifier has been developed. The bandwidth of FWM is > 300 GHz. For large wavelength separation between the input signals, where the nonlinear gain effects dominate the generation of FWM, the bandwidth of the FWM signal exceeds 1 THz. (C) 2000 American Institute of Physics. [S0021-8979(00)04405-4].

Stable mode-locked pulses with a repetition rate of 10 GHz were generated from an Er-doped fiber laser with a semiconductor optical amplifier in the cavity. By tuning the current of the semiconductor optical amplifier, complete harmonic mode-locking was obtained and the supermode noise in the RF spectrum of mode locked laser was removed for certain current range of the semiconductor optical amplifier.

Rational harmonic mode locking takes place in an actively mode-locked fiber laser when the modulation frequency f(m) = (n + 1/p)f(c), where n and p are both integers and f(c) is the inverse of the cavity round-trip time. the 22nd order of rational harmonic mode locking has been observed when f(m) approximate to 1 GHz. An optical pulse train with a repetition rate of 40 GHz has been obtained using a modulation frequency f(m) = 10 GHz, The theory of rational harmonic mode locking has also been developed. The stability of the mode-locked pulses is improved considerably when a semiconductor optical amplifier is incorporated into the fiber laser cavity. The supermode noise in the RF spectrum of a mode-locked laser is removed for a certain range of current in the semiconductor optical amplifier.