Thin film Fresnel lenses have been achieved on SiO(2)/Si substrates covered with a waveguide layer of Si(3)N(4) grown by low pressure chemical vapor deposition (LPCVD). The phase shift between the different zones is induced by a SiO(2) top layer chemically etched. The use of this additional layer having a smaller refractive index than the waveguide results in a saturation of the lens characteristics vs the thickness of the SiO(2) layer; this feature associated with the good reproducibility of the LPCVD technology allows good control of the lens characteristics.
A new micro-optical vibration sensor has been achieved by combining "integrated optics" and "micromachining" on silicon technologies. The high sensitivity and the wide frequency range have been obtained by using a multimode section in the optical detection circuit. Three prototypes have been installed successfully in an industrial hydroelectric power plant.
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