Vertical-cavity surface-emitting lasers with 14 GHz bandwidth

A maximum bandwidth of 14 GHz was observed in a study of small-diameter vertical-cavity surface emitting lasers (VCSELs). Gain-guided VCSELs from two wafers were used, nominally lasing at either 780 nm or 960 nm. Modulation experiments showed a very high frequency-square root of power coefficient D=10 GHz/mW/sup 1/2/. The maximum bandwidth of 13.7 GHz was reached at 20 degrees C (and 14.7 GHz at 7 degrees C) at a current of 8 mA for the 780 nm laser with a cavity diameter of 6 mu m. The cavity region of these lasers received both a broad area proton implant and a second deep implant centered at the active region to better define the cavity diameter. The 960 nm lasers received only the first broad area implant and their measured response of 10 GHz indicates the importance of minimizing lateral carrier diffusion.