Microstar cavities: An alternative concept for the confinement of light

In this Rapid Communication we report on an alternative concept to confine light in a microcavity. The traditional approaches are either based on total internal reflection at a dielectric interface or utilize a photonic band gap in a periodic structure such as Bragg mirrors or photonic crystals. In contrast, the concept presented here completely avoids these mechanisms. The light confinement is rather based on rays that are sequentially transmitted perfectly at the cavity's interface using Brewster's angle. These rays leave and reenter the cavity on closed periodic orbits without loss of intensity. Accordingly, in wave optics, high-quality modes with fascinating properties arise.