The operating principle of ICL is based on electrical injecting of electrons with further spatially indirect transitions between the conduction band in one semiconductor material and the valence band in a different semiconductor material. Despite the advances of contemporary technologies of commercial ICLs, allowing cw operation well above room temperature, the maximum output power still is limited by several factors. Clarification of these factors would provide important insight into the physical processes of ICL operation and, therefore, would open ways to overcome its limitations.
The authors of this Applied Optics article report a detailed cavity-length study of state-of-the-art ICLs emitting at two mid-IR wavelengths: ~ 3.45 μm, where ICL thresholds tend to be lowest and external differential quantum efficiency (EDQE) highest, and ~ 3.1 μm, where the performance typically becomes slightly less optimal for reasons not well understood at present. They found that the pronounced “efficiency droop” of the EDQE at high current densities is primarily due to an increase in the internal loss rather than a reduction in the internal efficiency. On the other hand, if the current density is fixed, the temperature variation of the EDQE is due primarily to a decrease of the internal efficiency.
Let us hope that these findings will suggest new ways for further ICL design improvements.
You must log in to add comments.