Masking mechanisms applied to thin-film coatings for the manufacturing of linear variable filters for two-dimensional array detectors.

We propose a method for manufacturing linear variable interference filters for two-dimensional (2D) array detectors, based on the use of correcting masks combining both rotation and translation movements of the masks and substrates. The major advantage of this method is its capability to produce several identical filters in a single run. 20 mm x 20 mm samples were manufactured with a wavelength ratio almost equal to 2 along the thickness gradient direction. In agreement with calculations, the measured uniformity perpendicular to the gradient is about 99.8% along 20 mm.

Transmission behaviors of single mode hollow metallic waveguides dedicated to mid-infrared nulling interferometry.

This paper reports the characterization of hollow metallic waveguides (HMW) to be used as single-mode wavefront filters for nulling interferometry in the 6-20microm range. The measurements presented here were performed using both single-mode and multimode conductive waveguides at 10.6microm. We found propagation losses of about 16dB/mm, which are mainly due to the theoretical skin effect absorption in addition to the roughness of the waveguide's metallic walls. The input and output coupling efficiency of our samples has been improved by adding tapers to minimize the impedance mismatch. A proper distinction between propagation losses and coupling losses is presented. Despite their elevate propagation losses, HMW show excellent spatial filtering capabilities in a spectral range where photonics technologies are only emerging.

Optical characterization of an unknown single layer: Institut Fresnel contribution to the Optical Interference Coatings 2004 Topical Meeting Measurement Problem.

We present the characterizations performed at the Institut Fresnel for the Measurement Problem of the Optical Interference Coatings 2004 Topical Meeting. A single layer coated on a fused-silica substrate of unknown composition and parameters is analyzed in terms of optogeometrical parameters, uniformity, and scattering. We determine the refractive index and the average thickness of the coating, then provide the localized determination of the thickness with a 2 mm spatial resolution. Topography measurements include atomic force microscopy and angle-resolved scattering measurements. These results are completed thanks to a Taylor Hobson noncontact 3D surface profiler.

Dedicated spectrophotometer for localized transmittance and reflectance measurements.

A dedicated spectrophotometer is built to achieve localized transmittance and reflectance measurements. The spatial resolution can be chosen from 100 microm to 2 mm, the spectral resolution from 0.5 to 5 nm, and the spectral range from 400 to 1700 nm. This apparatus can be used to study the index and thickness uniformity on single layers to determine and optimize the characteristics of the deposition chamber. It can also be used to measure the spatial variations of optical properties of intended nonuniform coatings such as linear variable filters.