Development of Energy-efficient Cryogenic Optical (ECO) data link

We develop an energy efficient digital data link connecting cryogenic superconducting single flux quantum (SFQ) circuits to room-temperature electronics. The design is based on low-temperature (4 K) superconductor ERSFQ SFQ/dc drivers, high-temperature superconductor data cables spanning 4 K to 70 K temperature stages, mid-temperature (70 K) polarization modulation vertical cavity surface emitting lasers (PM VCSELs), and fiber optic links to room temperature electronics. The Energy-efficient Cryogenic Optical (ECO) data link design is based on balancing power dissipation and signal gain at each temperature stage to maximize overall energy efficiency following the recently introduced Thermo-Gain Rule. To achieve VCSEL light emission with two switchable distinct polarization modes, a cruciform-shaped anisotropic optical cavity is formed by fabrication of a photonic crystal with etched periodic air holes surrounding the unetched cruciform region. In this report, we present the results of design, fabrication, and preliminary testing of the ECO data link components.