Diffraction symmetry of binary Fourier elements with feature sizes on the order of the illumination wavelength and effects of fabrication errors.

When building spot array binary Fourier diffractive optical elements (DOEs) having feature sizes on the order of the wavelength, we noticed remarkable variations in the experimental diffraction efficiency compared to the simulation results. Even with the use of high-cost electron beam lithography and rigorous Fourier modal method simulations, there appear to be no publications, to the best of our knowledge, showing close agreement in diffraction efficiency between the simulation and experimental results. In this Letter, we show that the diffraction symmetry of binary Fourier DOEs can be an efficient and consistent metric for evaluating the limit of the thin-element approximation and the effects of fabrication errors.

Smart multifunction diffractive lens experimental validation for future PV cell applications.

Recently, diffractive optical elements (DOE's) have attracted more attention for applications to third generation PV cells. Some DOE types can provide multiple functions such as spectrum splitting and beam concentration (SSBC) simultaneously. An off-axis diffractive lens has been designed and its ability to achieve the SSBC proved experimentally.

Iterative scalar nonparaxial algorithm for the design of Fourier phase elements.

We propose an iterative algorithm based on our scalar nonparaxial propagator for the design of Fourier diffractive optical elements (DOEs) having features on the order of the illumination wavelength. The simulation results show that our algorithm, using iterative Fourier transform and iterative projection, obtains higher-performance DOEs than a purely scalar paraxial design with the same order of calculation time. Upon verification with the experimental results, we find that our scalar-based design method is valid for DOEs with surprisingly small feature sizes (about half the wavelength) and diffraction angles up to about 37°.

Computationally efficient scalar nonparaxial modeling of optical wave propagation in the far-field.

We present a scalar model to overcome the computation time and sampling interval limitations of the traditional Rayleigh-Sommerfeld (RS) formula and angular spectrum method in computing wide-angle diffraction in the far-field. Numerical and experimental results show that our proposed method based on an accurate nonparaxial diffraction step onto a hemisphere and a projection onto a plane accurately predicts the observed nonparaxial far-field diffraction pattern, while its calculation time is much lower than the more rigorous RS integral. The results enable a fast and efficient way to compute far-field nonparaxial diffraction when the conventional Fraunhofer pattern fails to predict correctly.

A reliable, sensitive and fast optical fiber hydrogen sensor based on surface plasmon resonance.

We report for the first time on the experimental response of a Surface Plasmon Resonance fiber optic sensor based on wavelength modulation for hydrogen sensing. This approach of measuring the hydrogen concentration makes the sensor insensitive to intensity fluctuations. The intrinsic fiber sensor developed provides remote sensing and enables the possibility of multi-points sensing.

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.

Interferometric biosensor based on planar optical waveguide sensor chips for label-free detection of surface bound bioreactions.

A label free optical biosensor based on a free-space Young interferometer configuration is presented. Commercial planar Ta(2) O(5) waveguides are used as sensing elements and allow the investigation of surface bound bioreactions like immunoreactions or biological affinity systems. Design criteria are discussed and a detailed characterization of the sensor performance is presented.

Properties of a three-dimensional photonic jet.

By focusing light with a sphere several wavelengths in diameter, we can obtain a photonic nanojet [Opt. Express 13, 526 (2005)]: if light is focused on the surface of the sphere, the width of the beam stays smaller than the wavelength along a distance of propagation of approximately two wavelengths and reaches a high intensity. We use the rigorous Mie theory to analyze the basic properties of the photonic jet in the general three-dimensional polarized case.

Fringe pattern analysis with a parametric method for measurement of absolute distance by a frequency-modulated continuous optical wave technique.

Interferometry associated with an external cavity laser of long coherence length and broad wavelength tuning range shows promising features for use in measurement of absolute distance. As far as we know, the processing of the interferometric signals has until now been performed by Fourier analysis or fringe counting. Here we report on the use of an autoregressive model to determine fringe pattern frequencies.