Continuous-wave operation of 1.5μm InGaAs∕InGaAsP∕InP quantum dot lasers at room temperature

Continuous-wave operation at room temperature from InGaAs∕InGaAsP∕InP quantum dot (QD) laser diodes (LD) has been achieved. A ridge waveguide QD LD with 7 QD-stacks in the active region lases at 1.503μm at 20°C and that with 5 QD-stacks lases at 1.445μm at room temperature. The shift in lasing wavelength is believed to be due to the difference in the quantized energy states involved in producing gain for lasing. With smaller number of QD stacks and shorter cavity length, the lasing wavelength shifts to shorter wavelength indicating that more of higher excited states are involved in producing gain. By increasing the number of QD stacks to 15, lasing at 1.56μm has been achieved under pulsed mode.