Gain-cavity alignment in efficient visible (660 nm) VCSELs studied using high pressure techniques

Visible (600 nm) vertical-cavity surface-emitting lasers (VCSELs) for polym er fibre applications are very sensitive to temperature fluctuations and st ructural errors. Two devices with a 3 meV wavelength separation were studie d. Significant differences in the output performance can be explained by th e relative offset of the cavity mode and the peak of the gain spectrum. The different behaviour of the two devices as a function of hydrostatic pressu re can be explained by the gain-cavity offset. Temperature and pressure bot h shift the offset, but self-heating means that the cw variation is not alw ays as expected. Electron leakage also changes with both pressure and tempe rature, and in both cases its effect is dominant over the gain-cavity offse t in determining the threshold current variation.