Table of contents

An optical heterodyne polarization interferometer is described that can be efficiently used for the precision measurement of the phase shift induced by polarizing optical devices. This technique is used to measure the change with wavelength of a quarter-wave plate's retardation.

In this paper we discuss a simple yet inexpensive method to retrieve information on the path-length distribution of volume-reflected photons in non-absorbing turbid suspensions illuminated by a pencil-beam of monochromatic light. The method uses measurement of the radiance of volume-reflected light as a function of position and of absorption coefficient. The path-length distribution is connected to the radiance versus absorption behaviour via a Laplace transformation. We use an analytic expression that has been tested against Monte Carlo simulations to approximate the radiance versus absorption behaviour. The inverse Laplace transform of this function then gives us an approximation for the path-length distribution. It appeared that: (1) the average path-length close to the incoming beam is of the order of (s(1-g))^-1, and (2) observations in reflection cannot be studied using Monte Carlo simulations, as the acceptance cone does influence the path-length distribution of detected photons.

Modelling and optimization of non-linear multilayer all-optical devices including a grating coupler yield numerous prerequisite calculations in the linear regime. Indeed, it is of prime importance to know the influence of various physical and geometrical parameters (thickness and refractive index of each layer; grating groove depth, period and shape; angular spectrum of the input beam) on the diffraction properties. In this paper, it is shown how the well known (but often not well used) analytical Rayleigh-Fourier (RF) method can be used in many cases of practical interest, well above the validity limit generally admitted for a grating of sinusoidal shape (i.e. up to at least a groove depth equal to the grating period). Numerical problems due to the well known 'exponential overflow' due to evanescent waves are solved and so, up to 25 diffraction orders can be currently taken into account (up to 31 in some cases), whatever the number and thickness of substrate layers lying under the guiding grooved layer are. The use of equivalence rules for non-sinusoidal gratings is described. As a straightforward application of the plane wave calculation, the case of a finite beam is treated by taking advantage of its angular spectrum (a fast Fourier transform is used). The theoretical results obtained using the RF method are checked using the rigorous coupled wave method of Chateau and Hugonin. Finally, on a test example, dealing with a limited beam, we show that the diffraction efficiencies, calculated by the method we have implemented, are in perfect coincidence with those obtained experimentally.

Two- and multiple-beam interference fringes are used to measure the refractive index of graded index fibres. A general expression considering the refraction of the beam by the graded index fibre has been derived, from which expressions for homogeneous and skin-core fibres can be obtained. Comparison between the results with the method used when neglecting refraction is dealt with using Philips, LDF (TM) optical fibres and drawn polypropylene. Considering the derived expressions in the refractive index determination gives a correction even when a matching liquid is used, this suggests that the refraction method should be used especially for graded index fibre.

The position of a focal spot after transmission of a plane circularly polarized wave (e_x+i sigma e_gamma ) exp(ikz) through the half of a lens ( gamma >0) was investigated. The transverse shift Delta x approximately +or- sigma was found experimentally under switching of the sign of sigma . This effect is considered as the manifestation of spin-orbit interaction of a photon.

The phase shift between the two arms of a Michelson-type interferometer depends on the multilayer coatings deposited on the beam-splitter plate and the compensating plate. The phase shift thus induced is very dispersive. We propose a method in order to cancel the phase shift in which the beam-splitter coating is composed of two stacks. First we deposit an antireflection coating that is identical to those deposited on the three remaining faces, which compensates for the phase shift. Then we deposit a symmetrical stack that plays the part of the intensity beam-splitter. A numerical example is given for an interferometer working in the spectral range 3-5.5 mu m.

Pulses propagating in a non-linear dispersive (glass) fibre can be described by the non-linear Schrodinger equation if the pulse is longer than a picosecond; for shorter pulses, this equation must be extended. In this paper we systematically derive this extended equation using the method of multiple scales. By using an inherent freedom in the method of multiple scales, a technique is developed such that perturbation terms are greatly simplified. The limits of validity of the derived equation are discussed. It is shown to be valid for pulses longer than 30 fs.

A non-contacting optical profilometer is presented based on the principle of focus multiplexing by wavelength encoding due to a phase Fresnel lens. The decoding is performed by lateral dispersion. The surface profile is reconstructed after automatic point by point scanning with submicrometre height resolution.

Holography opens the way for a diffractive display of a wavefront recorded through an interference pattern. In this paper we proceed by an angular multiplexing method and we have recorded in dichromated gelatin (DCG), without any cross-talk effect, a matrix pattern of n*m*p, where n and m are rows and columns of the matrix and p is the multiplexing number. In our case n=7, m=10, p=16. The mechanism of hologram formation and gelatin processing is given. A sample illustration of cross-talk effect is shown and briefly explained. We then proceed by comparing only one among 16 multiplexed images to the original one through image processing.

Thermo-optic coefficients of the extraordinary effective refractive index in integrated optical channel waveguides in LiNbO₃ have been measured with high accuracy by Mach-Zehnder and Fabry-Perot interferometer techniques. Single mode titanium-indiffused and single mode annealed proton-exchanged (APE) channel waveguides were found to have the same value as it is known for the substrate material. Multimode proton-exchanged (PE) channel waveguides specially designed for maximum field overlap to the APE waveguides show a reduction of the thermo-optic coefficient to one-fifth with negative sign. Phase shift dependent on temperature was examined in APE channel waveguides containing such a strip-shaped multimode PE segment. Possible phase-compensated wavelength sensor applications are proposed.

An efficient and reliable method is presented for computing the eigenfunctions associated with scattering by elliptical cylinders. While the classical method is based on recurrence relations and infinite continued fractions, the new method is based on reformulating the computational task as an eigenvalue problem. In contrast with the classical method, the new method requires no initial estimates of the eigenvalues, and the computations can be performed using readily available computer library routines.