Thermal lensing effects in small oxide confined vertical-cavity surface-emitting lasers

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Abstract
The thickness and position of an oxide layer inside a vertical-cavity surface-emitting laser structure have been optimized for minimum optical scattering loss. In the resulting structure, the index guiding provided by the oxide aperture is very small. Consequently, for an oxide aperture radius <2 μm, the optical mode is only weakly confined. In devices using such small apertures, the formation of a thermal lens has a strong influence on optical guiding. The thermal lens leads to lower threshold currents and increased differential efficiency with continuous wave as compared to pulsed injection operation in devices with small apertures.