Characterization of 980-nm aged pump laser by using electrical and optical noise

Abstract

The knowledge of the noise levels is important for pump laser diodes as it allows to study and to locate the noise sources and their origin. 980 nm fresh and aged pump laser have been characterized by using electrical and optical noise measurements. In this work, we present the electrical and optical noises at low - medium frequency for fresh pump laser diodes emitting at 980 nm (reference laser), and we study the parametric evolution and the defects generated in aged 980nm single-mode ridge lasers, stressed during 400hrs at 50°C and high current injection (500 mA) (aged laser). The dynamic resistance, above threshold current, is not constant. It shows a proportionality of about RdμI-1/2. The injection of the carriers is associated to space charge limited current effect (SCLC). The study of the electrical and optical noise which represents the fluctuations of intensity at low and medium frequency is very significant of degradation of the active layer. The spectra are dominated by 1/f (fliker) noise at very weak current. And at weak current, the Current Noise Spectrale Density (CNSD) at 10 Hz is dominated by I3/2. The deffect is associated with carrier transport controlled by the interfaces n+n- and p+p- and the trapping defect density near the n+n- and p+p- interfaces, also it due to pinching of the space charge limited current SCLC effect An excess noise due to longitudinal mode hopping is related with output power fluctuations.