Quantum dots for high powers and efficiencies

Laser diodes based on planar quantum wells produce power conversion efficiencies that tend to saturate at room temperature at ~ 70%. These planar quantum well laser diodes have been heavily researched and developed and the power conversion efficiencies appear close to the material limits for optimized devices. The power conversion efficiency can be treated as a product of separate efficiencies based on drive voltage, injection efficiency, threshold loss, and internal optical absorption. In fact though these separate efficiencies are interdependent and fundamentally limited by the threshold current density. Electron-hole charge must be injected into the active material to reach threshold gain, which in turn establishes waveguide loss due to free carrier absorption, and voltage loss due to electron and hole mobilities transporting through the cladding layers and waveguide regions.