Two faces of superradiance in tandem-cavity ridge waveguide heterostructures

Cooperative emission due to spontaneous build-up and rapid decay of macroscopic polarization in a strongly inverted gain medium is drastically different from the lasing dynamics. The medium polarization and not the cavity field drives the emission from a device in semiclassical Maxwell-Bloch picture. Yet as pioneered by Dicke, the decay of the highest-energy state in a quantum ensemble of two-level systems proceeds through a ladder of the highest-symmetry partially deexcited states, each of which is formalistically an entangled state in mathematical sense. In this paper we summarize our experimental and theoretical studies on the two fundamental aspects of superradiance in multi-section tandem cavity laser heterostructures: (i) How can the superradiance be reached in semiconductor quantum wells albeit the ultrafast dephasing of individual microscopic e-h dipoles? (ii) Could the ensemble non-classicality be transferred to the emitted optical field and what could be the resulting photon state?