Figure 3.

Characteristics of the studied QCLs. L – resonator length, w – ridge width. (a) Voltage-current and light-current characteristics of QCLs grown on InAs. 1 – L = 3.5 mm, w = 21 µm; 2 – L = 2.3 mm, w = 14 µm; 3 – L = 1.2 mm, w = 17 µm; 4 – L = 0.7 mm, w = 17 µm. (b) Voltage-current and light-current characteristics of QCLs grown on Si. 1 – L = 3.0 mm, w = 20 µm; 2 – L = 1.5 mm, w = 16 µm; 3 – L = 1.15 mm, w = 15 µm; 4 – L = 0.6 mm, w = 14 µm. (c) Emission spectra of a QCL grown on Si measured at different temperatures.