Vertical-Cavity Surface-Emitting Lasers: Large Signal Dynamics and Silicon Photonics Integration

The GaAs-based vertical-cavity surface-emitting laser (VCSEL) is the standard light source in today’s optical interconnects, due to its energy efficiency, low cost, and high speed already at low drive currents. The latest commercial VCSELs operate at data rates of up to 28Gb/s, but it is expected that higher speeds will be required in the near future. One important parameter for the speed is the damping of the relaxation oscillations. A higher damping is affordable at low data rates to reduce signal degradation due to overshoot and jitter, while lower damping is required to reach higher data rates. A VCSEL with the damping optimized for high data rates enabled error-free transmission at record-high data rates of 57Gb/s over 1m optical fiber, 55Gb/s over 50m optical fiber, and 43Gb/s over 100m optical fiber. For future interconnect links it is of interest with tighter integration between the optics and the silicon-based electronics. Employing heterogeneous integration techniques to integrate GaAs-based VCSELs on silicon could potentially enable integrated multi-wavelength VCSEL arrays, thus increasing the data rate through parallelization. Heterogeneous integration of GaAs-based VCSELs would also benefit applications that need short-wavelength light sources, such as photonic integrated circuits for life sciences and biophotonics. By employing ultra-thin divinylsiloxane-bis-benzocyclobutene (DVS-BCB) bonding we have demonstrated silicon-integrated short-wavelength hybrid-cavity VCSELs with up to 1.6mW optical output power, with modulation bandwidth of 11GHz and capable of data transmission at data rates up to 20Gb/s.