Minimization of Damping in the Electrooptic Frequency Response of High-Speed Zn-Diffusion Single-Mode Vertical-Cavity Surface-Emitting Lasers

We utilize the Zn-diffusion technique to fabricate a single-mode high-speed 850-nm vertical-cavity surface- emitting laser. With this technique, we are able to minimize the thermal effect without greatly scaling down the diameter of the oxide- confined aperture. The demonstrated device has a 9- $\mu$m active diameter with which we can attain a bandwidth of 8 GHz, a small differential resistance ($\sim$47 $\Omega$), and a maximum output power of 3 mW. The single-mode characteristics can be sustained under dynamic operation for the whole bias current range. The dynamic measurement results indicate that with this single-mode device the damping-limited bandwidth of our multimode control can be eliminated without a Zn-diffusion aperture. A larger intrinsic bandwidth (32 versus 21 GHz) is also obtained due to the minimization of damping. The narrower divergence angle (8$^{\circ}$ versus 20$^{\circ}$ ) means that the device exhibits a larger alignment tolerance and much lower coupling loss (9 dB) when used with the standard multimode fiber than those of the control sample.