A theoretical look at coronagraph design and performance for direct imaging of exoplanets

New coronagraph concepts are being proposed at an increasing rate. In this article, I look at the intrinsic performance each concept can theoretically offer for direct detection of exoplanets. Fundamental physics sets quantifiable limits oil the performance of coronagraphs. This theoretical work provides valuable insight into how to design high performance coronagraphs, explains many of the characteristics of particular designs and reveals the importance of stellar angular diameter on coronagraph performance. This study shows that the PIAA coronagraph appears to be extremely attractive for direct imaging of exoplanets. Recent results obtained in the laboratory with this coronagraph are briefly presented.