Enhanced optical absorption in nanopatterned Yb-doped thin films for solid state laser application

The excitation and emission properties of optical materials can be adjusted by nanostructures and to achieve high optical efficiency in the optically pump laser with short absorption length and high threshold pump power, we present and theoretically investigate a Yb-doped thin film on a 1D grating structure in this paper. High reflectivity at the pump and emission wavelength are realized simultaneously and in terms of the guided-mode resonance theory, the local field of high reflected light is enhanced which will increase the absorption of associated laser wavelength. we analyze parameters of the nanostructure in detail based on rigorous coupled-wave theory and an appropriate structure is decided. We set up a simple quasi-three-level model and demonstrate that this designed structure can effectively improve the optical efficiency of optically pump solid state laser.