A compact four-wavelength Quantum Cascade laser source

A four-wavelength quantum cascade (QC) laser source that operates by using a single current channel is presented. The source includes two different heterogeneous QC lasers in two different waveguides, one with emission wavelengths of 7.0 mum/11.2 mum and the other with 8.7 mum /12.0 mum. Quantum cascade lasers with emission wavelengths of 8.7 mum, 11.2 mum and 12.0 mum have threshold current densities within around 15% of each other which allows them to be conveniently driven by a single current source.