  Nulling interferometry is a technique providing high angular resolution which
is the core of the space missions Darwin and the Terrestrail Planet Finder. The
first objective is to reach a deep degree of starlight cancelation in the range
6 -- 20 microns, in order to observe and to characterize the signal from an
Earth-like planet. Among the numerous technological challenges involved in
these missions, the question of the beam combination and wavefront filtering
has an important place. A single-mode integrated optics (IO) beam combiner
could support both the functions of filtering and the interferometric
combination, simplifying the instrumental design. Such a perspective has been
explored in this work within the project Integrated Optics for Darwin (IODA),
which aims at developing a first IO combiner in the mid-infrared. The solutions
reviewed here to manufacture the combiner are based on infrared dielectric
materials on one side, and on metallic conductive waveguides on the other side.
With this work, additional inputs are offered to pursue the investigation on
mid-infrared photonics devices.
