Dependence of the Device Performance on the Number of Stages in Quantum Cascade Lasers

The cascading scheme is a characteristic feature of quantum cascade (QC) lasers. It implies that electrons above threshold generate one photon per active region they successively traverse. This paper presents a study of the cascading behavior as a function of the number N of stacked active regions. 

Experimental results are presented for devices with N = 1, 3, 6, 12, 20, 30, 45, 60 and 75 active sages. The highest optical power and lowest threshold current density are obtained for laser devices with N as high as possible. However, the lowest threshold voltage and the lowest dissipated power at laser threshold are achieved for N = 3 and N - 22, respectively.