Condensed Matter Physics Seminar

Thursday, November 5, 1998, 3 p.m.
Physics Building, Room 1402

Stimulated emission and amplification in Josephson junction arrays

Paola Barbara

(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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