Oxide-Aperture Scaling of Cryogenic Microcavity Surface Emitting Laser for Ultrafast Optical Link

Abstract

The growth of cryogenic computing including quantum computers and superconducting processors requires energy-efficient data links capable of operating between room and cryogenic temperatures. In this work, we report the first high-speed microcavity laser achieved by scaling the oxide-aperture diameter of Cryo-VCSEL from 6.8 μm (typical cavity size) to 1.8 μm (microcavity) for ultrafast optical links. We investigated the scaling of laser cavity size through measurements of the oxide-aperture diameter and calculations of laser spectrum modal separation. The microcavity Cryo-VCSEL demonstrates an ultrahigh bandwidth, f-3dB > 50 GHz at a minimal bias current of 1mA (I/ITH = 3.5x) at 40 K. Furthermore, it achieves a 112 Gbps PAM-4 data rate with TDECQ = 3.30 dB at I = 6 mA, revealing that microcavity lasers are a viable solution for ultrafast data links, achieving energy efficiency of less than 10 fJ/bit.