Aims. We report results obtained with a four-quadrant and an eight-octant phase-mask coronagraphs (4QC and 8OC) produced using amplitude masks inside a Mach-Zehnder interferometer (MZI). We describe the laboratory implementation of these coronagraphs operated in laser light and provide a detailed comparison between theory and experiment. Methods. The +1 and -1 (π phase) amplitude transmissions required to produce a 4QC or an 8OC were obtained using complementary binary-masks (transmission of 1 or 0 for quadrants of similar parities) in the two arms of a MZI, taking advantage of the achromatic π phase shift between the two paths. In one output of the MZI, the reconstructed image of the focal plane is similar to those obtained for sectorised phase-masks coronagraphs, and the image of the aperture corresponds to the characteristic patterns of the 4QC/8OC coronagraphs. Results. Observations are compared with the theory published by other authors and developed further here. The expressions for the light diffracted outside the aperture image are simplified using the Zernike radial polynomials Z 1 n instead of the rapidly diverging hypergeometric functions otherwise used. Experimental results are found to be in very good agreement with the theory. With the present laboratory experiment, about 99% of the light is rejected outside the Lyot stop and the contrast obtained beyond 5λ/D is higher than 10 5 for both the 4QC and 8OC. As expected, the 8OC is less affected by a pointing error than the 4QC, but more sensitive to an aperture central obstruction. Incidently, the loss of transmission for a planet crossing two phase masks is given theoretically as a function of the Lyot stop size, in agreement with observations.

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Context. The quiet Sun exhibits a rich and complex magnetic structuring that is still not fully resolved or understood. Aims. We intend to contribute to the debate about the origin of the internetwork magnetic fields and whether or not they are related to the global solar dynamo. Methods. We analyzed center-to-limb polarization measurements obtained with the SOT/SP spectropolarimeter onboard the Hinode satellite outside active regions in 2007 and 2013, that is, at a minimum and a maximum of the solar cycle, respectively. We examined 10 × 10 maps of the unsigned circular and linear polarization in the FeI 630.25 nm line in regions located away from network elements. The maps were corrected for bias and focus variations between the two data sets. Then we applied a Fourier spectral analysis to examine wether the spatial structuring of the internetwork magnetic fields shows significant differences between the minimum and maximum of the cycle.