We have studied the characteristics of frequency response at 850-nm GaAs high-speed vertical-cavity surface-emitting lasers (VCSELs) with different kinds of oxide aperture sizes and cavity length using the PICS3D simulation program. Using 5-μm oxide aperture sizes, the frequency response behavior can be improved from 18.4 GHz and 15.5 GHz to 21.2 GHz and 19 GHz in a maximum of 3 dB at 25 °C and 85 °C, respectively. Numerical simulation results also suggest that the frequency response performances improved from 21.2 GHz and 19 GHz to 30.5 GHz and 24.5 GHz in a maximum of 3 dB at 25 °C and 85 °C due to the reduction of cavity length from 3λ/2 to λ/2. Consequently, the high-speed VCSEL devices were fabricated on a modified structure and exhibited 50-Gb/s data rate at 85 °C.

This study demonstrates a Zn-diffusion few-mode (FM) vertical-cavity surface-emitting laser (VCSEL) with a performance of the quasi-single-mode, SMSR over 20 dB. The VCSELs have a stable output power due to the larger oxide aperture because high-order transverse modes are suppressed through impurity-induced disordering of Zn-diffusion. The VCSEL has a 6 m oxide confined aperture diameter, and an Zn-diffusion aperture diameter of 4 m, depth of 1 m. It can reach a resonance frequency as high as 26.5 GHz at 9 mA and a modulation bandwidth exceeding 20 GHz. Error-free transmission at bit rates exceeding 50 Gbit/s with the encoded NRZ-OOK over 100 m of graded-index single-mode fiber (GI-SMF) is demonstrated.