Fundamentals of metasurface lasers based on resonant dark states

Abstract

Recently, our group proposed a metamaterial laser design based on explicitly coupled dark resonant states in low-loss dielectrics, which conceptually separates the gain-coupled resonant photonic state responsible for macroscopic stimulated emission from the coupling to specific free-space propagating modes, allowing independent adjustment of the lasing state and its coherent radiation output. Due to this functionality, it is now possible to make lasers that can overcome the trade-off between system dimensions and $Q$ factor, especially for surface emitting lasers with deeply subwavelength thickness. Here, we give a detailed discussion of the key functionality and benefits of this design, such as radiation damping tunability, directionality, subwavelength integration, and simple layer-by-layer fabrication. We examine in detail the fundamental design tradeoffs that establish the principle of operation and must be taken into account and give guidance for realistic implementations.