Optimization of thermal properties of etched-well surface-emitting GaAs/AIGaAs diode lasers

Abstract

Vertical cavity surface-emitting lasers (VCSELs) are known to suffer from excessive heating that seriously limits their cw performance. Recently, we have developed a self-consistent thermal electrical model of etched-well VCSELs, which features realistic distribution of heat sources and 2-D current and heat spreading.1 In this paper, we apply this model to optimize the device design with the goal of reducing the relative power loss from heating and maximizing the optical output power. The etched-well structure considered is similar to that described in Ref. 2, with a double-heterostructure active region defined by a blocking p-n-p junction. The primary parameter of interest is the active region diameter, since for small diameters the output power is expected to scale with the device size. Our calculations indicate that the optimal active region diameter, at which the heating effects are still relatively moderate, is ~16 μm. This value corresponds to a maximum excess of supplied power over the cw lasing threshold power at the corresponding active region temperature. Note that the maximum occurs in the middle of the operating current range, with the lower bound due to threshold for cw operation and the upper bound caused by thermal runaway.