THERMAL EFFECTS IN VERTICAL-CAVITY SURFACE-EMITTING LASERS

A comprehensive review of temperature-related effects and thermal modeling of vertical-cavity surface-emitting lasers (VCSELs) is presented. The paper is divided into two major parts. First, the effects of temperature on device characteristics are discussed, including the temperature dependence of the longitudinal mode spectra, the threshold current, the transverse-mode structure, and the output power. A new condition is formulated for thermal matching of the Bragg mirrors and the spacer region and a comparison is made between characteristic temperatures for the threshold current (T0) and for the external quantum efficiency (Tη). In the second part, various approaches to thermal modeling of VCSELs are described. Both simplified and comprehensive thermal models are considered and both analytical and numerical approaches are discussed. A new analytical approximate method for analysis of heat-flux spreading in multilayer structures is described. The most important results obtained with the aid of these models are presented. In particular, we show that the current dependence of thermal resistance is very sensitive to VCSEL structure, and is strongly influenced by the relative distribution of heat sources and their location with respect to the heat sink.