Abstract

Thermal effects play a key role in VCSELs. The relatively higher series resistance and the smaller active volume, with respect to conventional edge emitting lasers, make VCSELs much more sensitive to the temperature distribution and temperature fluctuations. Thermal lensing contributes to the transverse-mode selection even in oxide-confined devices. Polarization instability is strongly affected by thermal, as well as optical and electrical coupled effects. In spite of its importance, experimental determination of the actual temperature distribution inside a VCSEL are scarce. At today, the temperature of the active layer has been inferred, in most cases, by the wavelength shift of the laser emission. However, since the lasing modal pattern is not a local feature, but is rather determined by the gain profile and the optical field distribution inside of the whole structure, the information provided by this kind of measurements is necessarily averaged over the cavity volume. To our knowledge, the only attempt to locally measure the temperature distribution of VCSEL has been made by Luo et al. using a thermal scanning microscope [1]. While allowing for high spatial resolution (~100 nm), this technique required the cleaving of the device thus changing its working point.

© 2001 EPS