Ultrafast Zn-Diffusion and Oxide-Relief 940 nm Vertical-Cavity Surface-Emitting Lasers under High-Temperature Operation

We demonstrate 940-nm vertical-cavity surface-emitting lasers (VCSELs) with record-high -3 dB electrical-to-optical bandwidths of 40 and 32 GHz under room-temperature and 85 °C operations, respectively. The combination of Zn-diffusion with oxide-relief apertures inside the VCSEL cavity structure can greatly reduce the differential resistance and parasitic capacitance, which leads to an enhancement in the resistance-capacitance (RC)-limited bandwidth. Devices with different sizes of oxide-relief apertures are analyzed by use of the measured S₂₁ and S₁₁ two-port scattering parameters and equivalent circuit modeling techniques. For a device with a 3-μm diameter oxide-relief aperture, the extracted intrinsic bandwidth can be as high as 46.3 GHz. By using this novel device as the transmitter, we can achieve 60 Gbps error-free [bit-error-ratio (BER) <1 × 10^-12] on-off keying transmission over a 1-m OM5 fiber under room temperature (RT) operation, without using any signal processing. In addition, invariant 50-Gbps transmission performance from RT to 85 °C operations, over a 100-m OM5 fiber has also been successfully demonstrated (with a BER < 1 × 10^-7).