Broadband Vector Vortices for High Contrast Coronagraphy

The requirement of detecting nearly ten orders of magnitude smaller signal of a planet compared to the nearby star puts forward extreme challenges for coronagraphs designed for exoplanet imaging. Vector vortex waveplates (VWs) appear to be capable of providing best performance compared to other mask technologies due to their structure as thin film coatings of continuous texture that minimizes light scattering noises and wavefront distortions even for high topological charge values. The nature of VWs as half-wave phase retarders provides opportunities of having high diffraction efficiency in a broad band of wavelengths in different parts of spectrum, from UV to IR.The pathways of reaching the ultimate performance features of VWs have proven elusive so far due to the great multitude of fundamental and technological factors influencing them. The Phase 1 study allowed us to identify architectures overcoming tradeoffs of contrast vs bandwidth, and relating those to manufacturability and tolerances. The unique knowledge gained in the Phase 1 on fundamental and technological issues of developing high contrast VWs will be used to setup fabrication and optical characterization systems adequate for meeting tolerances and specifications required for coronagraphs. The development will address technologies of multilayer liquid crystal polymers with precisely tuned intrinsic alignment and retardation. The fabrication systems would be enhanced with high precision coating, alignment, and curing systems in fully controlled environmental conditions, and with automated key processes for quality and yield. Direct contrast characterization systems in large dynamic range would complement high precision special test equipment with custom built opto-electronic systems.