SPECTRALLY-FILTERED ELECTROLUMINESCENCE OF VERTICAL-CAVITY SURFACE-EMITTING LASERS

We show that spontaneous emission from the mirror layers (lambda = 780 nm) of a vertical cavity surface emitting laser (VCSEL) is a signific ant component of the spectrum, By using bandpass filters, we are able to distinguish the electroluminescence (or ''near-field'') pattern of the mirror layers from the active region pattern, We show that in some lasers, these patterns are irregular, possibly due to the presence of absorbing doping or defect clusters in the p-mirror that absorb light from the active region, and re-radiate the light at the shorter wavel ength characteristic of the mirror layers, In addition, we show that d ark areas appear, both in the active regions and the mirrors, as the d evice degrades.