The authors demonstrate a spatially chirped emission wavelength in ver
tical cavity surface emitting laser (VCSEL) arrays grown by molecular
beam epitaxy. The wavelength shift is due to a lateral thickness varia
tion in the Al0.2Ga0.8As cavity, which is induced by a substrate tempe
rature profile during growth. A 20 nm shift in lasing wavelength is ob
tained in a VCSEL array.