Ion-exchange on glass is now a mature integrated optics technology, indeed, many devices such as wavelength multiplexers, splitters, optical amplifiers, lasers or sensors have been already realized. The challenge is now to integrate all these functions on a single chip. Two different paths can be used to achieve this goal : the first one consists in a reduction of the waveguides’ dimensions by an increase of the refractive index change, whereas the second one, which is addressed in this paper, is based on the realization of multilayered devices. Because ion-exchange on glass allows manufacturing either surface or buried waveguides, this technology is well adapted for 3D integration. However, it is mandatory to prevent any parasitic light transfer between top and bottom waveguides. This condition can be fulfilled if they are sufficiently separated. In this article, we present the development of ion-exchanged waveguides deeply buried into a glass substrate and their application to 3D integrated devices. They have been realized by means of a two steps Ag+/Na+ ion-exchange on a dedicated silicate glass. First, a thermal ion-exchange has been carried out at 330°C during 2 min in a 0.8NaNO3-0.2AgNO3 molten salt in order to create the core of the waveguide; then this core has been buried into the glass substrate by applying an electric field of 450 V/m during 1h30min in a NaNO3 solution at 260°C. The obtained waveguide has been measured to be 22 µm under the glass surface. It is singlemode at λ=1.55µm. In order to prove the good isolation between this waveguide and the surface, a top layer has been added to the device by the realization of surface channel waveguides through a thermal ion-exchange performed in a 0.8NaNO3-0.2AgNO3 molten salt at 330°C during 2 min. The near-field observation of the device output has shown no coupling between the top and bottom layers demonstrating therefore the feasibility of 3D integrated optical devices by means of ion-exchange on glass.

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1. Hybrid Neodymium-doped passively Q-switched waveguide laser
2. Study ion of Ag+/Na+ ion-exchange diffusion on germanate glasses : Realization of single-mode waveguides at the wavelength of 1.55 µm.