High-speed MBE-grown 1550 nm wafer-fused VCSELs

We study high-power high bit rate single-mode 1550 nm vertical-cavity surface-emitting lasers fabricated using wafer-fusion. The optical cavity was grown on an InP wafer, and the two AlGaAs/GaAs distributed Bragg reflectors were grown on GaAs wafers, all three by molecular-beam epitaxy. The active region is based on thin InGaAs/InAlGaAs quantum wells and a composite InAlGaAs tunnel junction. To confine current and optical radiation, we use a lateral-structured buried tunnel junction with ≈ 6 µm diameter and an etching depth of ≈ 20 nm. These VCSELs demonstrate up to 5 mW single-mode continuous-wave output power and a threshold current of ≈ 2 mA at 25 °C. Even at an ambient temperature of 85 °C, the maximum optical output power is larger than 1 mW. The lasers demonstrate a 34 Gbps non-return-to-zero data transfer rate and 42 Gbps (21 GBaud) using 4-level pulse amplitude modulation at 25 °C back-to-back conditions with ≈ 934 fJ/bit power consumption per bit, which is amongst the lowest values reported for this wavelength range and bit rate.