  Arrays of 10 nm-diameter point contacts of exchange-coupled
spin-majority/spin-minority ferromagnetic metals, integrated into
infrared-terahertz range photon resonators, are fabricated and measured
electrically and optically. Giant, threshold-type electronic excitations under
high-current pumping of the devices are observed as abrupt but reversible steps
in device resistance, in many cases in access of 100%, which correlate with
optical emission from the devices. The results are interpreted as due to
stimulated spin-flip electron-photon relaxation in the system.
