  Superconductor-based light-emitting diode (superconductor-based LED) in
strong light-confinement regime are characterized as a superconductor-based
three-terminal device, and its transport properties are quantitatively
investigated. In the gate-controlled region, we confirm the realization of
new-type Josephson field effect transistor (JoFET) performance, where the
channel cross-sectional area of the junction is directly modulated by the gate
voltage. In the current-injected region, the superconducting critical current
of $\mu$A order in the Josephson junction is found to be modulated by the
steady current injection of pA order. This ultrahigh monitoring sensitivity of
the radiative recombination process can be explained by taking into account the
fact that the energy relaxation of the absorbed photons causes the conversion
of superconducting pairs to quasiparticles in the active layer. Using
quasiparticle density and superconducting pair density, we discuss the carrier
flows together with the non-equilibrium superconductovity in the active layer
and the superconducting electrodes, which take place for compensating the
conversion.
