THz emission at 80 Kelvin from stacked Bi₂Sr₂CaCu₂O₈ Intrinsic Josephson Junctions

The extremely anisotropic high-temperature superconductor Bi₂Sr₂CaCu₂O₈ contains stacked 'intrinsic' Josephson junctions with a large superconducting gap energy. Mesa-shaped devices constructed from this material are therefore a promising source of coherent, continuous-wave radiation in the 'terahertz gap' range. However, a key issue for technological applications of these devices is their cryocooling requirements, and it is therefore highly desirable to optimize their performance to allow them to operate at 77 Kelvin or above. Here we report generation of 40 microwatts of coherent emission power at 0.45 THz at a bath temperature of 80 Kelvin. This was achieved by exciting the (3, 0) cavity mode of a stack containing 580 junctions and with dimensions 300 × 180 × 0.9 μm³. The device was heatsunk using PbSn solder and a copper substrate. We discuss the choice of mesa dimensions, and the implications of the choice of the cavity mode for THz-frequency dissipative losses - and therefore THz generation - close to the device's superconducting critical temperature of 86.5 Kelvin.