Effects of Bragg mirror interface grading and layer thickness variations on VCSEL performance at 1.55 μm

Improved simulation of VCSEL distributed Bragg reflectors

“…In order to compare the proposed method with well known TMM, CMT, and Tanh methods, the VCSEL test structure presented in [7] and sketched in Fig. 1 has been considered.…”

“…Moreover, L cav is the laser cavity length, α cav is the optical cavity loss, g 0 is the material gain coefficient, J 0 is the transparency current density and η int is the internal quantum efficiency. Numerical values are taken from [7]. Tables 4-8 show the comparisons among different numerical methods in terms of reflectivity, threshold gain, threshold current density and external quantum efficiency.…”

Accurate modelling of VCSEL distributed Bragg reflectors by Floquet-Bloch theory

“…We have considered the structure analysed in [27] to calculate the reflectivity and compare results obtained by FBT, TMM and CMT (see Fig. 2).…”

“…This is simply done by modifying the coupling constant, but the introduction of some approximations is necessary, so the applicability of the method is limited to the DBR structures with little index difference, where the perturbation induced by the grating is usually weak. Linnik et al [27] used an Airy functions-based approach for graded interfaces as a modified TMM method. Moreover, Corzine et al [29] developed a tanh substitution technique for determining the reflectivity of abrupt and graded multilayered mirrors.…”

“…Thermal heating and consequent deterioration of laser performance is connected with the high series resistance of DBR stacks, due to the large band gap difference at the hetero-interfaces resulting in impediment of the carrier flow. In order to reduce series resistance, different approaches have been used: graded interfaces, heavy doping, parabolic grading and modulation doping [27]. The exact reflectivity of a particular DBR depends on the exact alloy composition and doping scheme used.…”