Stable single-mode operation of an 850-nm VCSEL with a higher order mode absorber formed by shallow Zn diffusion

We report that an 850-nm vertical-cavity surface-emitting laser with a planar higher order mode absorber, formed by shallow Zn diffusion (<0.3 μm), operated at stable single-mode over the entire drive current range. A device with a 5×5 μm² absorber aperture and a 5×5 μm² oxide confined active region showed a /spl sim/0.8 mA threshold and a mode suppression ratio of 40 dB. The modeling indicates that the higher order modes will be suppressed strongly due to the much larger threshold gain, compared to that of the fundamental mode as long as the Zn diffusion depth outside the 5×5 μm² absorber aperture is over /spl sim/0.2 μm, which agrees well with the experimental results.