20-Gbps 1300-nm range wafer-fused vertical-cavity surface-emitting lasers with InGaAs/InAlGaAs superlattice-based active region
S. A. Blokhin, A. V. Babichev, A. G. Gladyshev, I. I. Novikov, A. A. Blokhin, M. A. Bobrov, N. A. Maleev, V. V. Andryushkin, Dmitrii V. Denisov, K. O. Voropaev, V. M. Ustinov, V.E. Bougrov, A. Yu. Egorov, L. Ya. Karachinsky
Abstract
1300-nm vertical-cavity surface-emitting lasers (VCSELs) were fabricated by wafer fusion (WF) technique and studied. The active region based on InGaAs/InAlGaAs superlattice was grown by molecular-beam epitaxy (MBE). Current and optical confinement was provided by composite n ++ -InGaAs / p ++ -InGaAs / p ++ -InAlGaAs buried tunnel junction (BTJ) realized by selective etching and overgrowth by n-InP. AlGaAs/GaAs distributed Bragg reflectors grown by MBE were applied on both sides of the cavity by WF and substrate removal techniques. The devices with BTJ diameter of 5 μm demonstrated a stable single-mode lasing with threshold current <1.3 mA and output optical power >6 mW and operation in a wide temperature range. The measured −3 dB bandwidth was more than 8 GHz at 20°C and about 5.5 GHz at 85°C, the eye diagrams were open with a bit rate up to 20 Gbps using nonreturn-to-zero (NRZ) modulation standard at 20°C. Using 5-tap feedforward equalizer, the NRZ transmission at 25 Gbps was demonstrated up to 5 km single-mode fiber at 20°C. The developed VCSELs represent a platform for further significant performance improvement.