X-shooter is a wide band (U to K) intermediate resolution (4000-14000) single object three-arms spectrograph for
the VLT. Currently in the last phase of integration, X-shooter will see the first light at ESO Paranal as the first of the
VLT second generation instruments in the last quarter of 2008. We describe in this paper the final steps in the
integration and testing phase of the central Backbone with its key functions (including the active flexure
compensation mirrors) and of the two UV-Blue and Visible spectroscopic arms. We report on the stability results of
the preslit optics and of the spectrographs and on the remarkable efficiency which is derived from the measurements
of the optical components of the instrument.
X-shooter is a single target spectrograph for the Cassegrain focus of one of the VLT UTs where it will start to operate in
2008. The instrument covers in a single exposure the spectral range from the UV to the K' band. It is designed to
maximize the sensitivity in this spectral range through the splitting in three arms with optimized optics, coatings,
dispersive elements and detectors. It operates at intermediate resolutions (R=4000-14000, depending on wavelength and
slit width) with fixed echelle spectral format (with prism cross-dispersers) in the three arms. The project has completed
the Final Design Review in June 2006. In this status report, the overall concept is summarized and new results on the
dichroics, the active flexure compensation system, the operation modes and the expected performance are given. The
instrument is being built by a Consortium of Institutes from Denmark, France, Italy and the Netherlands in collaboration
with ESO. When in operation, its wide spectral range observing capability will be unique at very large telescopes.
A nonlinear nonlocal model for beam propagation in a liquid
crystal is analyzed. Using a perturbative approach interactions
between in-phase and out-of-phase solitons is described
analytically. Attraction of both in-phase and out-of-phase
solitons is predicted. The perturbative approach also predicts the
existence of a stable bound state of two out-of-phase solitons.
The analytical results are verified by direct numerical