Low noise characteristics of VSIS lasers in single-longitudinal mode

Low noise characteristics of semiconductor lasers are reguired for optical disk systems. In generally, single longitudinal mode lasers originate large mode competition noise as the gain envelope shifts with tempurature. Still more, feedback-induced noise of a single-mode laser occur, when a little portion of the laser output reflected by an external mirror is fed back into the laser cavity1). To improve this noise characteristics, it is important to stabilize the longitudinal mode in index guided laser2). This stabilization would be atained with gain suppression of nonlasing modes caused by nonlinear optical interactions with the lasing mode3)4).