High slope efficiency and low noise characteristics in tapered-active-stripe DFB lasers with narrow beam divergence

We report high slope efficiency and low noise characteristics in a distributed feedback (DFB) laser lasing at 1.3 /spl mu/m with narrow beam divergence by employment of a laterally tapered active stripe over the whole cavity. This tapered structure is designed to realize narrow beam divergence, low threshold current, and high longitudinal mode selectivity. The fabricated tapered-active-stripe DFB lasers demonstrated of 9.20/spl times/13.40 and a record slope efficiency, for a narrow beam DFB laser, of 0.59 mW/mA. The temperature characteristics from -10/spl deg/C to 85/spl deg/C shows high output power at high temperature, stable single longitudinal mode oscillation and stable far-field patterns. Furthermore, for the first time ever, a low relative intensity noise characteristic of under -155 dB/Hz has been realized when butt-coupling into a single-mode fiber.