Reflectance mapping with microsphere-assisted white light interference nanoscopy.

The characterisation of novel materials presents a challenge that requires new and original developments. To face some of these demands for making measurements at the nanoscale, a new microsphere-assisted white light interference nanoscope performing local reflectance mapping is presented. This technique presents the advantages of being non-destructive, full-field and label-free.

High-quality manipulable fiber-microsphere for super-resolution microscopy.

Despite the gain in resolution brought by microsphere (MS)-assisted microscopy, it has always faced several limitations, such as a limited field of view, surface defects, low contrast, and lack of manipulability. This Letter presents a new type of MS created at the tip of an optical fiber, which we call a fiber microsphere (fMS). The fMS is made from a single-mode or coreless fiber, molten and stretched, ensuring high homogeneity and a sphere diameter smaller than the fiber itself.

Characterization of Functional Materials Using Coherence Scanning Interferometry and Environmental Chambers.

Functional materials are challenging to characterize because of the presence of small structures and inhomogeneous materials. If interference microscopy was initially developed for use for the optical profilometry of homogeneous, static surfaces, it has since been considerably improved in its capacity to measure a greater variety of samples and parameters. This review presents our own contributions to extending the usefulness of interference microscopy.

Wide-field parallel mapping of local spectral and topographic information with white light interference microscopy.

Fourier analysis of interferograms captured in white light interference microscopy is proposed for performing simultaneous local spectral and topographic measurements at high spatial resolution over a large field of view. The technique provides a wealth of key information on local sample properties. We describe the processing and calibration steps involved to produce reflectivity maps of spatially extended samples.

Coherence scanning interferometry allows accurate characterization of micrometric spherical particles contained in complex media.

Characterizing very small particles, from a few dozen micrometers to the nanometric scale, is a very challenging application in a wide range of domains. In this work, we demonstrate, through the recovery of silica and polystyrene bead properties (i.e.

Depth-resolved local reflectance spectra measurements in full-field optical coherence tomography.

Full-field optical coherence tomography (FF-OCT) is a widely used technique for applications such as biological imaging, optical metrology, and materials characterization, providing structural and spectral information. By spectral analysis of the backscattered light, the technique of spectroscopic-OCT enables the differentiation of structures having different spectral properties, but not the determination of their reflectance spectrum. For surface measurements, this can be achieved by applying a Fourier transform to the interferometric signals and using an accurate calibration of the optical system.

Modeling the specular spectral reflectance of partially ordered alumina nanopores on an aluminum substrate.

Anodizing of aluminum generates a porous alumina layer comprising cylindrical nanopores (300 nm diameter) extending essentially perpendicular to the substrate. The pore distribution over the surface exhibits a short-distance order close to hexagonal arrangement. On the contrary, long-distance order cannot be defined: the arrangement is not periodic.

Fabrication of optical mosaics mimicking human corneal endothelium for the training and assessment of eye bank technicians.

The determination of endothelial cell density (ECD) is a crucial activity in eye banks for the assessment of corneal tissue quality. These cells are responsible for corneal transparency, and ECD correlates with graft survival. ECD is mainly assessed with a manual "naked-eye" procedure under a transmitted light microscope in Europe and using a specular microscope in the United States.

Comparison of the behavior of a subwavelength diffractive lens in TE and TM polarization allowing some nonstandard functions.

This Letter introduces and discusses a difference in the behavior of a cylindrical diffractive lens encoded with subwavelength structures illuminated with monochromatic coherent light in the cases of TE and TM polarization. The effective medium theory is used to model with new binary phase function the diffractive lens. A new algorithm combines the finite-difference time domain for the propagation in the near field and the radiation spectrum method for the propagation in the far field.

Modeling of the angular tolerancing of an effective medium diffractive lens using combined finite difference time domain and radiation spectrum method algorithms.

A new rigorous vector-based design and analysis approach of diffractive lenses is presented. It combines the use of two methods: the Finite-Difference Time-Domain for the study in the near field, and the Radiation Spectrum Method for the propagation in the far field. This approach is proposed to design and optimize effective medium cylindrical diffractive lenses for high efficiency structured light illumination systems.

Comparison of the efficiency, MTF and chromatic properties of four diffractive bifocal intraocular lens designs.

The aim of this paper is to compare the properties of four different profiles which can be used as multifocal intraocular lens. The Hankel transform based on the theory of scalar diffraction is applied to a binary profile, a parabolic one, a parabolic profile with holes, and finally a sinusoidal one. This enables to study the various distributions of the diffractive efficiencies and the axial chromatism.

Ultrashort laser pulse splitting upon resonant reflection on a mirror-based waveguide grating.

A resonant waveguide grating based on a high reflectivity mirror causes a 2pi phaseshift of adjustable slope in the spectrum of an ultrashort light pulse, giving rise to a controllable, lossless temporal pulse splitting. This monolithic phase shifter can simply be placed on the path of the beam as a mirror. A functional element was designed and fabricated.

Spectral phase induced by the reflection on a mirror-based waveguide grating in the neighborhood of modal resonance.

A linearly polarized plane wave impinging on a mirror-based waveguide grating is shown to experience a 2pi phase shift of controllable slope in the reflection spectrum. Such a zeroth-order resonant grating effect is adequately confirmed by means of an ellipsometer. The close agreement between the analytical representation of grating coupled waveguide resonances with the experimental results confirms the relevance of the underlying phenomenological understanding of resonant gratings.

Multi-level diffractive optical elements produced by excimer laser ablation of sol-gel.

Material ablation by excimer laser micromachining is a promising approach for structuring sol-gel materials as we demonstrate in the present study. Using the well-known direct etching technique, the behaviour of different hybrid organic/inorganic self-made sol-gel materials is examined with a KrF* laser. Ablated depths ranging from 0.

High-efficiency, broad band, high-damage threshold high-index gratings for femtosecond pulse compression.

High efficiency, broad-band TE-polarization diffraction over a wavelength range centered at 800 nm is obtained by high index gratings placed on a non-corrugated mirror. More than 96% efficiency wide band top-hat diffraction efficiency spectra, as well as more than 1 J/cm(2) damage threshold under 50 fs pulses are demonstrated experimentally. This opens the way to high-efficiency Chirped Pulse Amplification for high average power laser machining by means of all-dielectric structures as well as for ultra-short high energy pulses by means of metal-dielectric structures.

Bridging pole and coupled wave formalisms for grating waveguide resonance analysis and design synthesis.

The algebraic polar expression of resonant reflection from a grating waveguide excited by a free space wave is formulated in terms of the physically meaningful phenomenological parameters of the coupled wave formalism. The reflection coefficient is simply represented as a circle in the complex plane which sheds light on the behaviour of the modulus and phase of anomalous reflection. Analytical expressions are derived for the phenomenological parameters that can now be calculated from optogeometrical quantities which are simple to measure.