Low-threshold (≤ 92 A/cm2) 1.6 μm strained-layer single quantum well laser diodes optically pumped by a 0.8 μm laser diode

To explore the ultimate threshold current limit in long-wavelength semiconductor lasers, InxGa1−xAs/InP strained-layer single quantum well laser diodes were studied for the first time by optically pumping with a 0.8 μm laser diode. Low-threshold (≤92 A/cm2) cw operation was obtained and the lasing wavelength (1.62 μm) corresponding to the transition from the first quantization state of a 25 Å In0.8Ga0.2As well was observed. By taking the carrier collection efficiency (≤77%) into account, the actual threshold current density could be as low as 70 A/cm2.