Thin film Fresnel lenses have been achieved on SiO2/Si substrates covered with a waveguide layer of Si3N4 grown by low pressure chemical vapor deposition (LPCVD). The phase shift between the different zones is induced by a SiO2 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 SiO2 layer; this feature associated with the good reproducibility of the LPCVD technology allows good control of the lens characteristics.
© 1981 Optical Society of America
P. Mottier and S. Valette, "Integrated Fresnel lens on thermally oxidized silicon substrate," Appl. Opt. 20, 1630-1634 (1981)