Fig. 1. Refractive index profile and simulated optical field intensity inside the designed 850 nm VCSEL cavity

Fig. 2. （a）SEM image of the cross section of the device after wet oxidation, the dark lines are the oxidized high-Al-composition layers,（b）top-view of fabricated VCSEL with ground-signal-ground（GSG）probe pads

Fig. 3. （a）L-I-V curves of VCSEL with 5 μm oxide aperture at room temperature,（b）lasing spectra at different bias currents

Fig. 4. （a）Small signal modulation response S₂₁ curve of 850 nm VCSEL at different current values at room temperature,（b）square relation of VCSEL relation oscillation frequency and -3 dB modulation bandwidth to current above threshold

Fig. 5. （a）The bit error rate tests of device in PRBS7 and PRBS31 codes at the transmission distance of 1 m fiber, the figure on the right: optical eye diagram in PRBS7 and PRBS31 codes at 50 Gbit/s,（b）the bit error rate tests of device in PRBS7 and PRBS31 codes at the transmission distance of 100 m fiber, the figure on the right: optical eye diagram in PRBS7 and PRBS31 codes at 40 Gbit/s

Fig. 6. Bath curves of the device tested by NRZ modulation using PRBS7 code,（a）bath curves at the transmission distance of 1 m fiber of 40 Gbit/s data transfer rate,（b）bath curves at the transmission distance of 100 m fiber of 40 Gbit/s data transfer rate