Condensed Matter Physics Seminar
Thursday, November 5, 1998, 3 p.m.
Physics Building, Room 1402
Stimulated emission and amplification in Josephson junction arrays
(Center for Superconductivity Research, UMD)
Abstract: We detected mm-wavelength radiation from two-dimensional
arrays of underdamped Josephson junctions. All of our samples emit coherently
in a novel synchronized state, which is triggered by a resonance in the
array structure. Measurements of the detected power as a function of the
number N of active junctions show a threshold, suggesting population inversion.
Above threshold, the power scales quadratically with N up to an array size
bigger than the free space radiation wavelength. The highest measured conversion
efficiency from DC to AC power is about 17%. Our data are consistent with
stimulated emission causing coherence and cannot be explained by existing
classical coupling mechanisms.
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