Cryogenic Performance Projections for Ultra-small Oxide-free Vertical-cavity Surface-emitting Lasers

Small-sized vertical-cavity surface-emitting laser (VCSEL) may offer very low power consumption along with high reliability for cryogenic data transfer. Cryogenic data transfer has application in supercomputers and superconducting for efficient computing and also focal plane array cameras operating at 77 K, and at the lower temperature of 4 K for data extraction from superconducting circuits. A theoretical analysis is presented for 77 K and 4 K operation based on small cavity, oxide-free VCSEL sizes of 2 to 6 µm, that have been shown to operate efficiently at room temperature. Temperature dependent operation for optimally-designed VCSELs are studied by calculating the response of the laser at 77 K and 4 K to estimate their bias conditions needed to reach modulation speed for cryogenic optical links. The temperature influence is to decrease threshold for reducing temperature, and to increase differential gain for reducing temperature. The two effects predict very low bias currents for small cavity VCSELs to reach needed data speed for cryogenic optical data links. Projections are made for different cavity structures (half-wave cavity and full-wave cavity) shown that half-wave cavity structure has better performance. Changing the number of top-mirror pairs has also been studied to determine how cavity design impacts speed and bit energy. Our design and performance predictions paves the way for realizing highly efficient, ultra-small VCSEL arrays with applications in optical interconnects