A Survey of Transparent Conducting Films and Optoelectrical Materials for High Optical Power Applications

The lifetime laser damage performance of a wide range of transparent conductive materials is assessed, including ultrathin metal films, doped metal oxides, doped compound semiconductors, and graphene whose carrier densities span five orders of magnitude from 1018 to 1023cm-3. Lifetime laser damage thresholds are determined by exposing material surfaces to repeated nanosecond laser pulses at near IR wavelengths (1064 nm). Near threshold fluences, two distinct damage modes, i.e., bulk and discrete, emerge depending on carrier density. These bulk and discrete damage modes are attributed to free carrier-induced bulk and localized, defect-driven absorption processes, respectively. For polycrystalline films with free carrier densities greater than ≈1020 cm-3, laser damage thresholds are less than 5 J cm-2. In contrast, bulk absorption is not apparent at thresholds substantially higher than ≈10 J cm-2 in single-crystal films with free carrier concentrations lower than ≈1019cm-3. By increasing thickness, films with lower carrier densities can deliver relevant levels of sheet conductance (