  The discovery of an Earth-mass exoplanet around the nearby star Proxima
Centauri provides a prime target for the search for life on planets outside our
solar system. Atmospheric characterization of these planets has been proposed
by blocking the starlight with a stellar coronagraph and using a
high-resolution spectrograph to search for reflected starlight off the planet.
Due to the large flux ratio and small angular separation between Proxima b and
its host star ($\lesssim10^{-7}$ and $\lesssim2.2\lambda/D$ respectively; at
750nm for an 8m-class telescope) the coronagraph needs to have a high starlight
suppression at low inner-working angles. We aim to find the global optimum of
an integrated coronagraphic integral-field spectrograph. We present the
Single-mode Complex Amplitude Refinement (SCAR) coronagraph that uses a
microlens-fed single-mode fiber array in the focal plane downstream from a
pupil-plane phase plate. The mode-filtering property of the single-mode fibers
allows for the nulling of starlight on the fibers. The phase pattern in the
pupil plane is specifically designed to take advantage of this mode-filtering
capability. Second-order nulling on the fibers expands the spectral bandwidth
and decreases the tip-tilt sensitivity of the coronagraph. The SCAR coronagraph
has a low inner-working angle ($\sim1\lambda/D$) at a contrast of
$<3\times10^{-5}$ for the 6 fibers surrounding the star using a
sufficiently-good adaptive optics system. It can operate over broad spectral
bandwidths ($\sim20\%$) and delivers high throughput ($>50\%$ including fiber
injection losses). Additionally, it is robust against tip-tilt errors
($\sim0.1\lambda/D$ rms). We present SCAR designs for both an unobstructed and
a VLT-like pupil. The SCAR coronagraph is a promising candidate for exoplanet
detection and characterization around nearby stars using current
high-resolution imaging instruments.
