Numerical analysis of transverse mode in gain-guided vertical cavity surface emitting lasers

The stability of the fundamental transverse mode in a multiquantum-well vertical cavity surface emitting laser (VSCEL) has been studied by simulation. A full self-consistent model is presented for the VCSELs including the refractive index and the gain changes due to temperature rise and carrier variation in the gain medium. The nonuniform finite difference method is employed to solve the two-dimensional wave equation and simulate the behaviour of the VCSELs on desktop computers. The limitation to the maximum single mode power stems from the appearance of the higher-order transverse mode for the broad-area lasers, and the gain reduction caused by heating the small-area lasers. The self-focusing resulting from the spatial hole burning has a strong impact on the fundamental mode size. The calculations show that there are optimum values for both the quantum-well number and the conductive path diameter. Based on the chosen parameters a laser with three quantum wells and about 6 μm diameter conductive path yields the largest single mode output power