Passively Modelocked Laser With Tunable Pulse Repetition Frequency in a Semiconductor Optical Amplifier

We present the experimental demonstration of a pulse repetition frequency tunable passively mode-locked laser using semiconductor optical amplifier as the gain medium. The laser is designed for the 1550-nm telecommunication applications. The mode-locking mechanism is explained in terms of normal mode splitting of the continuous-wave spontaneous emission signal from the semiconductor optical amplifier. The splitting arises from the coupling between a quantum cavity, represented by the semiconductor gain medium, and an optical cavity comprised of a high-birefringence fiber in line with a Faraday mirror. Experimental results are presented for pulse repetition frequency tunability ranging between 93 and 1400 MHz, as well as for the pulse width which is measured to be 343 ps. These results are shown to compare favorably with theoretical calculations.