  Specific high contrast imaging instruments are mandatory to characterize
circumstellar disks and exoplanets around nearby stars. Coronagraphs are
commonly used in these facilities to reject the diffracted light of an observed
star and enable the direct imaging and spectroscopy of its circumstellar
environment. One important property of the coronagraph is to be able to work in
broadband light.
  Among several proposed coronagraphs, the dual-zone phase mask coronagraph is
a promising solution for starlight rejection in broadband light. In this paper,
we perform the first validation of this concept in laboratory.
  First, we recall the principle of the dual-zone phase mask coronagraph. Then,
we describe the high-contrast imaging THD testbed, the manufacturing of the
components and the quality-control procedures. Finally, we study the
sensitivity of our coronagraph to low-order aberrations (inner working angle
and defocus) and estimate its contrast performance. Our experimental broadband
light results are compared with numerical simulations to check agreement with
the performance predictions.
  With the manufactured prototype and using a dark hole technique based on the
self-coherent camera, we obtain contrast levels down to $2\,10^{-8}$ between 5
and 17$\,\lambda_0/D$ in monochromatic light (640 nm). We also reach contrast
levels of $4\,10^{-8}$ between 7 and 17$\lambda_0/D$ in broadband
($\lambda_0=675$ nm, $\Delta\lambda=250$ nm and $\Delta\lambda / \lambda_0 =
40$ %), which demonstrates the excellent chromatic performance of the dual-zone
phase mask coronagraph.
  The performance reached by the dual-zone phase mask coronagraph is promising
for future high-contrast imaging instruments that aim at detecting and
spectrally characterizing old or light gaseous planets.
