High efficiency quasi-three level thin film laser enabled on a sinusoidal grating substrate

The excitation and emission properties of optical materials can be adjusted by nanostructures and to achieve high optical efficiency in the optically pump laser, especially for lasers with short absorption length and high pump threshold. 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. Finally, we demonstrate that this designed structure can effectively improve the optical efficiency of optically pump solid state laser.