The invention takes regard for an innovative fabrication method of planar optical guide lenses, obtained by proton exchange in various cuts of LiNbO₃. It pertains to the integrated optics technological field for the manufacturing of devices for real time processing of wide band RF signals. The process consists of thermal treatment followed by exchange of protons, in a diluted solution which serves to alter the refraction index of the guided mode in a controlled manner. Such alteration, which is obtained through thin film masking, provides geometries and reticulations for the manufacturing of lenses and of other planar integrated optical components.

Method for the fabrication of LiNbO3 single mode planar optical guide lenses

Procedure for the manufacture of optical wave guides for the ordinary refractive index of Lithium Niobate by means of a double ion exchange. A layer several microns thick is generated with an initial deep proton exchange, from which a certain fraction of the lithium ions has been extracted from the material, causing a reduction in the ordinary index of approximately δn [approximately equals] 0.04 (Fig. 1). With a second, less deep exchange than the first, in a lithium-rich solution, the lithium ions are re-introduced and the ordinary index approximately recovers its initial value in a layer less than the first. This last layer together with the rest of the previous layer which forms the actual substrate, constitutes the wave guide (Fig. 2). The wave guide finally has a jump in the ordinary index of δn [approximately equals] 0.03 for λ = 0.6328 μm.

Procedure for the manufacture of optical wave guides for the ordinary refractive index of LiNbO3.

Optical waveguides in lithium compound optoelectronic substrate material are defined by a two-stage process In the first stage of this process the lithium compound substrate is selectively exposed to a proton source and such that hydrogen and lithium ions are exchanged In the second stage of this process, the substrate is immersed in a molten metal saft to define a stabilized region of higher refractive index Substrates of the lithium compound lithium niobate, may be treated by immersion in molten benzoic acid followed by immersion in a potassium salt, for example potassium nitrate

Bennion Ian

Papers

Manufacture of an optical waveguide using ion exchange