Optical Energy Transfer and Loss Mechanisms in Coupled Intracavity Light Emitters

Despite the near-unity internal quantum efficiencies (IQEs) demonstrated for GaAs-based light emitters, laser cooling of the ubiquitous III-V semiconductors has not been feasible. The key challenges for III-V optical cooling are the reduced absorption of optical excitation at photon energies well below the bandgap and the strong confinement of light in the high refractive index semiconductors. Here, we investigate the possibility to eliminate the need for light extraction and to eventually relax the requirements of the IQE. This is done using electroluminescence and optical energy transfer within intracavity devices consisting of an AlGaAs/GaAs double heterojunction light emitting diodes and a GaAs p-n-homojunction photodiode enclosed within a single semiconductor cavity. We measure the intracavity energy transfer, i.e., the coupling quantum efficiency (CQE) between the two diodes and estimate loss mechanisms by simultaneously measuring the IV characteristics of the emitter diode and the photocurrent of the absorber diode. The measured CQE of our devices is below 60% due to the mirror, light extraction, nonradiative, and detection losses. While this is far below the state-of-the-art efficiencies, our results suggest that it will be possible to substantially improve the efficiency by adopting the fabrication and design principles used for the best performing photoluminescent emitters.