Diamond subwavelength gratings for mid-infrared AGPM coronagraph: manufacturing assessment

We present the manufacturing and measurement results obtained with a mid-infrared (L-band ~ 3.8 µm) diamond Annular Groove Phase Mask (AGPM) coronagraph (Mawet et al 20051), using subwavelength gratings and diamond-optimized micro-fabrication techniques such as Nano-Imprint Lithography and Reactive Ion Etching

Comparison of metal/polymer back reflectors with half-sphere, blazed, and pyramid gratings for light trapping in III-V solar cells

We report on the fabrication of diffraction gratings for application as back contact reflectors. The gratings are designed for thin-film solar cells incorporating absorbers with bandgap slightly lower than GaAs, i.e. InAs quantum dot or GaInNAs solar cells. Light trapping in the solar cells enables the increase of the absorption leading to higher short circuit current densities and higher efficiencies. We study metal/polymer back reflectors with half-sphere, blazed, and pyramid gratings, which were fabricated either by photolithography or by nanoimprint lithography. The gratings are compared in terms of the total and the specular reflectance, which determine their diffraction capabilities, i.e. the feature responsible for increasing the absorption. The pyramid grating showed the highest diffuse reflection of light compared to the half-sphere structure and the blazed grating. The diffraction efficiency measurements were in agreement with the numerical simulations. The validated model enables designing such metal/polymer back reflectors for other type of solar cells by refining the optimal dimensions of the gratings for different wavelength ranges

Halo suppression in full-field x-ray Zernike phase contrast microscopy

Visible light Zernike phase contrast (ZPC) microscopy is a well established method for imaging weakly absorbing samples. The method is also used with hard x-ray photon energies for structural evaluation of material science and biological applications. However, the method suffers from artifacts that are inherent for the Zernike image formation. In this Letter, we investigate their origin and experimentally show how to suppress them in x-ray full-field ZPC microscopy based on diffractive x-ray optics

Zernike x-ray ptychography

We present an imaging technique combining Zernike phase-contrast imaging and ptychography. The contrast formation is explained by following the theory of Zernike phase-contrast imaging. The method is demonstrated with x-rays at a photon energy of 6.2 keV, showing how ptychographic reconstruction of a phase sample leads to a Zernike phase-contrast image appearing in the amplitude reconstruction. In addition, the results presented in this Letter indicate an improvement of the resolution of the reconstructed object in the case of Zernike ptychography compared with the conventional one

Surface plasmons carry a pancharatnam-berry phase

Surface plasmon polaritons (SPPs) are electromagnetic surface waves that travel along the boundary of a metal and a dielectric medium. They can be generated when freely propagating light is scattered by structural metallic features like gratings or slits. In plasmonics, SPPs are manipulated, amplified, or routed before being converted back into light by a second scattering event. In this process the light acquires a dynamic phase, and possibly an additional geometric phase associated with polarization changes. We examine the possibility that SPPs can mediate a geometric Pancharatnam-Berry phase, and find that this is indeed the case. Moreover, the geometric phase is shown to survive the light → SPP → light process

Expanding the applicability domain of phase-mask lithography of gratings to the extreme

International audienceThe applicability domain of phase-masks for the manufacturing of gratings is widely expanded by breaking the limits of a so far very narrow spatial frequency spectral width. This is a result of searching for high index deep-UV film materials and of resorting to a novel phase-mask scheme at the large period side

Phase-mask grating printing to extremes

International audienceThe very restricted range of grating periods printable by standard silica phase-masks is here extended from close to the 45 nm CD-node to arbitrarily large periods by the appropriate choice of material and interference-generating scheme with a potential for unlimited length and wide area

Towards tender X-rays with Zernike phase-contrast imaging of biological samples at 50 nm resolution

X-ray microscopy is a commonly used method especially in material scienceapplication, where the large penetration depth of X-rays is necessary for three-dimensional structural studies of thick specimens with high-Z elements. In thispaper it is shown that full-field X-ray microscopy at 6.2 keV can be utilized forimaging of biological specimens with high resolution. A full-field Zernike phase-contrast microscope based on diffractive optics is used to study lipid dropletformation in hepatoma cells. It is shown that the contrast of the images iscomparable with that of electron microscopy, and even better contrast at tenderX-ray energies between 2.5 keV and 4 keV is expected