b
Fig. 2 Electrical and optical characteristics of a
conventional QCL and a QCL with π-shape electrode during CW operation.
a P-I-V characteristics for various heat sink temperatures
b CW spectra for various pumping currents at 20 °C.
At 20 °C, the device exhibited a threshold current of 400 mA and a
maximum CW output power of 141 mW. The traditional QCL have a maximum
output power of 148 mW. According to the I-V characteristic curve of the
device, it can be calculated that the differential resistance above the
threshold current is about 5 Ω. Figure 2b we present the CW lasing
spectra of the QCLs at 20 °C and the injection current is 440 mA. The
device exhibits multimode lasing with a center wavelength around 8.5µ m.