HOT-VELM: A Comprehensive and Efficient Code for Fully Vectorial and 3-D Hot-Cavity VCSEL Simulation

A model to simulate vertical-cavity surface-emitting laser (VCSEL) operation above threshold is presented. The power-current (PI) curves are computed while accounting for mode competition arising from spatial hole-burning and temperature profiles. The latter affect many laser parameters, such as the gain spectra and the optical modes, which change their shapes and wavelengths during operation. The aim of this comprehensive model is to describe the details of VCSEL operation above threshold in non circularly symmetric geometries by preserving at the same time computational efficiency. The optical treatment is vectorial, using the in-house developed three dimensional (3-D) code. The model is based on a solution of the rate equations for field-carrier interactions. Similarly to the mature vectorial optical treatment, the numerical efficiency is achieved by expanding all the involved 3-D variables (current profiles, carrier densities, temperature and optical fields) in basis of simple analytical functions. The model is tested on a structure which has an epitaxial design based on a real device and a transverse geometry suitable to put in evidence all its 3-D features. In particular, the carrier expansion technique is validated by comparison with the commonly used carrier meshing procedure. The heating mechanisms are illustrated in detail and the effects which rule the power rollover and laser turn-off are compared and discussed within an improved injection model.