Energy efficiency of 1.55-µm vertical-cavity surface-emitting lasers with an active region based on strained InGaAs/InAlGaAs quantum wells

Subject of study. This study examines vertical-cavity surface-emitting lasers (VCSELs) operating at 1.55 µm, based on strained InGaAs/InAlGaAs quantum wells. These VCSELs were fabricated using wafer-fusion (WF) technology to bond distributed Bragg reflector heterostructures with an optical cavity grown by molecular beam epitaxy (MBE). Aim of study. The aim was to assess the energy efficiency of information transmission using 1.55-µm VCSELs, fabricated using a combination of WF and MBE techniques, across a wide range of bit rates from 5 Gbits/s to 30 Gbits/s. Method. The method involved recording eye diagrams at various bit rates for VCSELs under large-signal amplitude modulation and estimating the effective modulation bandwidth and dynamic energy efficiency of the lasers via small-signal analysis. Main results. The results showed that minimum energy consumption (0.83 pJ/bit) was achieved at a bit rate of 20 Gbits/s, which is consistent with theoretical predictions. Further increasing the operating current to support higher bit rates resulted in a sharp increase in energy consumption, as the modulation bandwidth increased more slowly than did the energy input. At the maximum tested bit rate of 30 Gbits/s, where an open eye diagram was still observed, the energy efficiency decreased to 1.2 pJ/bit. Practical significance. These findings are significant for the development of energy-efficient, high-speed fiber-optic transceivers based on 1.55-µm VCSELs.