Efficient reversible phase mask for TiO2 submicron gratings directly printed on cylindrical surfaces.

In this article we present a radial phase mask specially designed and manufactured for direct micro-structuration under UV photolithography of a cylindrical surface covered by a photoresist TiO2 film. The period of the phase mask is sub-micron (between 480 nm and 720 nm) and allows direct printing on several types of cylindrical components. With this dedicated reversible phase mask we have demonstrated the feasibility of a TiO2 grating with a period of 960 nm, printed on a SiO2 cylinder or inside a SiO2 tube of 8 mm diameter.

Large Area Fabrication of Periodic TiO2 Nanopillars Using Microsphere Photolithography on a Photopatternable Sol-Gel Film.

The authors demonstrate a unique low cost process to print 2D, submicron size, and high refractive index nanopillars using a direct colloidal-photolithography process. A well collimated i-line source emitting at 365 nm wavelength illuminates a mono layer of silica microspheres of 1 µm diameter deposited on a photosensitive TiO2-based sol-gel layer. No etching process is needed since this layer is directly UV photo patternable like a negative photoresist. Furthermore, this thin layer offers interesting optical properties (high refractive index and optical transparency) and good mechanical and chemical stability and thus can be directly used as a functional microstructure (for PV or sensor applications, for example). The paper describes the modeling of the electric field distribution below the spheres during the illumination process, the photochemistry of the TiO2 sol-gel layer process, and preliminary results of TiO2 nanopillars of around 200 nm in diameter fabricated on a three-inch substrate.

Subwavelength cylindrical grating by holistic phase-mask coordinate transform.

A periodic grating with an integer number of periods is fabricated at the resist-coated wall of a cylinder by exposing a circularly symmetrical planar high index phase mask to a cylindrical wave. This extends the spatial coherence features easily achievable in a planar 2D space to the 3D space of cylindrical waves and elements.

Interfaces detection after corneal refractive surgery by low coherence optical interferometry.

The detection of refractive corneal surgery by LASIK, during the storage of corneas in Eye Banks will become a challenge when the numerous operated patients will arrive at the age of cornea donation. The subtle changes of corneal structure and refraction are highly suspected to negatively influence clinical results in recipients of such corneas. In order to detect LASIK cornea interfaces we developed a low coherence interferometry technique using a broadband continuum source. Real time signal recording, without moving any optical elements and without need of a Fourier Transform operation, combined with good measurement resolution is the main asset of this interferometer. The associated numerical processing is based on a method initially used in astronomy and offers an optimal correlation signal without the necessity to image the whole cornea that is time consuming. The detection of corneal interfaces - both outer and inner surface and the buried interface corresponding to the surgical wound - is then achieved directly by the innovative combination of interferometry and this original numerical process.

Spatially and polarization resolved plasmon mediated transmission through continuous metal films.

The experimental demonstration and characterization is made of the plasmon-mediated resonant transmission through an embedded undulated continuous thin metal film under normal incidence. 1D undulations are shown to enable a spatially resolved polarisation filtering whereas 2D undulations lead to spatially resolved, polarization independent transmission. Whereas the needed submicron microstructure lends itself in principle to CD-like low-cost mass replication by means of injection moulding and embossing, the present paper demonstrates the expected transmission effects on experimental models based on metal-coated photoresist gratings. The spectral and angular dependence in the neighbourhood of resonance are investigated and the question of the excess losses exhibited by surface plasmons is discussed.

Low coherence interferometry for central thickness measurement of rigid and soft contact lenses.

In this paper we propose contact lens central thickness measurement with a low coherence interferometry technique using either a SLED source or a broadband continuum generated in air-silica Microstructured Optical Fiber (MOF) pumped with a picosecond microchip laser. Each of these sources associated with the interferometer provides, at the same time, good measurement resolution and quick signal recording without moving any optical elements and without need of a Fourier Transform operation. Signal improvement is performed afterwards by a numerical treatment for optimal correlation peaks detection leading to central thickness value of several contact lenses.

Broadband supercontinuum interferometer for high-resolution profilometry.

In this paper, it is shown that a white light supercontinuum source generated in an air-silica microstructured optical fiber pumped with picosecond pulses offers the possibility to improve fringes visibility in interferometric acquisitions. Consequently, this source combined with a spectral interferometer, reaches high-resolution profilometric measurements. Phase calculation based on seven point algorithm can perform theoretically a subnanometer resolution. This method provides a one line profile of large surfaces from the analysis of a single shot image, without any mechanical scanning.

Imaging through a scattering medium with an interferential spectrometer by selection of an amplitude modulation correlator.

Low-coherence interferometric systems provide three-dimensional imaging through scattering media by measurement of the object's temporal response. An optical correlator is presented that allows direct recording of the signal issued from the object under reflection. The filtering technique enhances the image visibility and allows one to obtain an image with a good signal-to-noise ratio. The performance of two particular imaging systems, point-to-point and vertical-slice imaging, is discussed with an object comprising two cover plates that are attached.

High-resolution optical correlation imaging in a scattering medium.

An optical correlation setup is used to image transparent objects through scattering media, and 10-mum longitudinal and 2.5-mum transverse resolution are achieved. Spectral-bandwidth sampling of the light source is made possible by a tunable dye laser and leads to signal enhancement as a result of sampling interferogram filtering. An optical system allows observation of sample slices without the need for a translation stage.

Examination and comparative study of a simple method to determine the left ventricular ejection fraction.

The authors developed a simple radioisotopic method for determining the left ventricular ejection fraction with 99mTc-labelled red blood cells. The semi-quantitative data is acquired at the equilibrium stage and gated to the ECG. The results of this atraumatic and reproducible isotopic determination of LVEF correlate statistically well those of echocardiography and left ventricular angiography.