A broad band mirror system and method, wherein the system includes a mechanical substrate layer, a reflective metal layer on the mechanical substrate level, and a diamond layer, and the method includes the steps of selecting a sacrificial substrate layer, depositing a diamond layer on the substrate layer, smoothing a first surface of the diamond layer, depositing a reflective metal layer on the diamond layer, bonding a mechanical substrate to the diamond layer, removing the sacrificial substrate level, and smoothing a second diamond surface.