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Content archived on 2024-04-19



A new coupled-mode theory of nonlinear interactions at grating couplers has been developed and applied to second harmonic generation using sub-wavelength gratings.
Basic experiments have been performed concerning i) second harmonic generation using sub-wavelength gratings, ii) nonlinear directional couplers using polymers and iii) electrooptic modulation of light with grating couplers.
Concerning these three experiments, early experimental results show the interest of associating guided wave nonlinear optics, gratings and polymers.

A full electromagnetic analysis of diffraction process during the photolithographic transfer of a chromium mask has been developed at both infinite conductivity mask and for real metals. By studying the influence of the various optogeometrical parameters on the field intensity map below the mask it has become possible to extend the lighting conditions described in the Roumiguieres-Neviere patent for periodic masks to nonperiodic devices, like Fresnel zone plates and focusing gratings.

The fabrication of binary and blazed waveguide coupling gratings was performed successfully. The highest coupling efficiencies achieved are 67% in the case of incoupling by means of an sub-wavelength binary grating and 74% for outcoupling from a wave-guide into one diffraction order via a blazed coupling grating. Focussing and beam shaping properties of such gratings were demonstrated experimentally. For the future we see interesting applications for high-frequency binary gratings and, therefore, a great demand for further research in fabrication and inspect ion technology for such gratings.

The oblique incidence lithography was demonstrated on a modified standard mask aligner: 0.4 mm period, two millimetre square gratings were easily transferred on four inch waveguide wafers. Special waveguide like focusing grating and double frequency grating are also transferred in the same condition due to the large tolerance in angle and in period that were demonstrated. The fabrication of high diffraction efficiency grating and demonstrators for industrial applications in metrology and biochemical microsystems were achieved.

1. Two-period grating with even period ratio N provide balanced excitation of two waveguide modes.
2. Effective excitation of the waveguide mode by the light beam incident from the air can be achieved with the help of parallelogramic grating.
3. For effective operation of the waveguide grating it is necessary to ensure that the dissipative and scattering losses are small.
The objective of the project is to give the practical answer to the key question of the access to and from a monolithic integrated optic chip from and to an extended volume wave by means of a high efficiency, wave front shaping coupling grating.

Monolithic planar optics is bound to take the place of micro-optics in the new generation of optical modules and systems in metrology and consumer industry because of lower assembling costs, lower weight and better stability. This potential can only be valorized if the access problem is solved with efficiency and flexibility.

The project deals with coplanar coupling gratings at the conceptual, modelling and technological levels. It brings the preconditions for industrial applications of integrated optics ad it also realizes the conditions for the achievement of high efficiency, then possibly useable nonlinear effects in waveguides and waveguide gratings.

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