Concept of the InGaAs Plasmonic Waveguide for Quantum Cascade Laser Applications

Quantum cascade lasers are sophisticated devices mostly based on InGaAs/AlInAs/InP heterostructures to improve thermal performance. Their structure consists of a core containing hundreds or even thousands of thin layers, covered on both sides with thick cladding waveguides. Such a laser design creates enormous stresses in the core and can cause degradation of the entire device. An alternative to the thick InP claddings are thin, highly doped InGaAs layers used as plasmonic waveguides. This solution allows to achieve a mode confinement above 50 % even at only 150 nm of the waveguide layer, which is extremely difficult in the case of standard designs. The article presents theoretical simulations concerning the influence of the InGaAs plasmonic layer on the mode confinement.