Contents I. Introduction
Active mode locked laser (MLL) use cavity loss modulation to generate short optical pulses [1]. MLLs are widely used for high speed optical communication, optical clock recovery, optical time division multiplexing, optical analog to digital conversion etc [2]–[4]. The laser is said to be mode locked when the round trip cavity time is an exact multiple of modulation period, i.e . The variation of MLL from its exactly matched condition is called detuning of the laser. The pulsewidth and peak power of active mode locked laser are minimum and maximum respectively under the detuned condition, whereas the peak power of output pulses decreases from its maximum and pulsewidth increases from its minimum value [5], [6]. Detuning in active mode locked lasers is caused by a change of modulation frequency by small step size due to thermal and mechanical perturbations. Detuning causes instability in pulses, pulse width broadening, phase noise, and output power reduction, pulse shape distortion [6]. Therefore, the dynamics of MLL under detuned condition and the locking range of an active MLL are of importance in understanding MLL stability. Several studies have reported analysis of MLL under detuning in which the laser was detuned by changing the modulation frequency. These studies have reported a detuning bandwidth or locking range of a few kHz [7].
