Design and simulation of an electrically tunable quantum dot cascade laser

We present here a novel design to form an artificial quantum dot with electrical confinement and apply it to a Quantum Cascade Laser structure to realize a Quantum Dot Cascade Laser. A two-dimensional finite element method has been used to numerically simulate the novel design of electrical formation of an artificial quantum dot. The size of the quantum dot is electrically tunable and can be applied to quantum cascade laser structure to reduce the non-radiative LOphonon relaxation. Numerical modeling with cylindrical symmetry is custom developed using Comsol multiphysics to evaluate the electrical performance of the device and optimize it by varying design parameters, namely, the doping density of different layers and thickness of the cladding and active regions. The typical s-, p-, dand fwave functions have been calculated. Numerical simulations show that the energy level separation could be as large as 50 meV by electrical confinement. We also demonstrate the road map for the fabrication of such a device using a maskless super lens photolithography technique. We have achieved a uniform array of nano-contacts of size ~ 200nm, required for the device, using photolithographic technique with a UV source of λ ~ 400nm. The entire processing involves 7 photolithographic steps. This new device “Quantum dot cascade laser”, promises low threshold current density and high wall-plug efficiency. Index terms – quantum cascade laser (QCL), quantum dot (QD), quantum dot cascade laser (QDCL), super lens lithography (SLL).