Lasing of a quantum-cascade laser with a thin upper cladding

Experimental results on the manufacturing and study of the properties of 7–8 $\mu$m wavelength range injection quantum-cascade lasers (QCLs) with a waveguide with a thin top cladding layer based on indium phosphide are presented. The heterostructure is formed by molecular beam epitaxy on an InP substrate, with a In$_{0.53}$Ga$_{0.47}$As/Al$_{0.48}$In$_{0.52}$As active region. Lasing at a wavelength of 7.8 $\mu$m at a temperature of 300 K with a threshold current density of $\sim$6 kA/cm$^2$ is obtained. Characteristic temperature $T_0$ and $T_1$ values for the QCLs are about 150 K and 450 K, respectively. Obtained results confirm the promising design of the QCLs with a waveguide with a thin top cladding layer for detecting liquids and microfluidic devices development.