  The Optimal Optical CoronagraphWorkshop at the Lorentz Center in September
2017 in Leiden, the Netherlands gathered a diverse group of 25 researchers
working on exoplanet instrumentation to stimulate the emergence and sharing of
new ideas. This contribution is the final part of a series of three papers
summarizing the outcomes of the workshop, and presents an overview of novel
optical technologies and systems that are implemented or considered for
high-contrast imaging instruments on both ground-based and space telescopes.
The overall objective of high contrast instruments is to provide direct
observations and characterizations of exoplanets at contrast levels as extreme
as 10^-10. We list shortcomings of current technologies, and identify
opportunities and development paths for new technologies that enable quantum
leaps in performance. Specifically, we discuss the design and manufacturing of
key components like advanced deformable mirrors and coronagraphic optics, and
their amalgamation in "adaptive coronagraph" systems. Moreover, we discuss
highly integrated system designs that combine contrast-enhancing techniques and
characterization techniques (like high-resolution spectroscopy) while
minimizing the overall complexity. Finally, we explore extreme implementations
using all-photonics solutions for ground-based telescopes and dedicated huge
apertures for space telescopes.
