Cryogenic Oxide-VCSEL for PAM-4 Optical Data Transmission Over 50 Gb/s at 77 K

To meet the rising demand for a high-speed and power-efficient optical link for cryogenic data operation, we report a 6.8- μm oxide-aperture VCSEL with a record bandwidth ≥50 GHz at cryogenic temperatures. A high-speed packaged oxide-VCSEL demonstrates optical data transmission capability from 12.5 to 44 Gb/s NRZ and 51.56 Gb/s PAM-4 at 77K.