Low-noise 650-nm-band AlGaInP visible laser diodes with a highly doped saturable absorbing layer

Stable self-sustained pulsating and low-noise 650-nm-band AlGaInP visible laser diodes were demonstrated by adopting a novel structure, which has a highly doped saturable absorbing (SA) layer. Short carrier lifetime, which is indispensable for self-pulsation, was realized by applying high doping concentration to the p-type SA layer. 500-μm-long devices with 51%/51% coated facets were fabricated, resulting in the threshold current of 75 mA at 20°C. The temporal output power was measured at the average output power of 5 mW and the stable self-pulsation was observed up to an ambient temperature of 60°C. Therefore, the relative intensity noise (RIN) was kept about -140 dB/Hz in temperature ranging from 20°C to 60°C. Since the refractive index difference could be kept large and the optical mode could be confined effectively, the astigmatism in this work was below 3 μm at 5 mW against dc injection current. The lasers operated over 1350 h under the average output power of 5 mW at 60°C