The ioNext industrial platform from Teem Photonics uses an ion-exchange phenomenon which occurs between glass wafers and molten salt baths when these are suitably brought into contact. This phenomenon locally increases the optical index of the glass by modifying its composition. While the transparency of the glass offers low propagation losses comparing to other integrated optics technologies, the versatility of the ion-exchange process allows to control the mode size of the waveguide along its length, its interaction with the surface, as well as its polarization properties or wavelength behavior
A silicate glass is an amorphous SiO2 matrix populated with various other elements. Most of them contains alkaline ions which are weakly bonded to the matrix. As a consequence, when a heated glass wafer is immersed in a molten salt bath containing other ions like K+, Ag+ or Tl+, an ion-exchange process between the glass and the bath can take place at the glass surface. Once ions from the bath penetrate into the glass, they can move into the silica matrix through thermal diffusion or electrical conduction processes.
The ion-exchange process leads to the change of the glass composition and properties close to its surface. One affected property is the local refractive index. The refractive index variation can be brought about by both ionic polarizability and radius differences between the exchanged ions.
The table below sums up the features of the most widely used couples of exchanged ions:
Teem will select the best species couple and the adapted process depending on your custom request (operating wavelength, loss, compactness, PER, interaction with glass surface,...
Teem Photonics waveguide manufacturing process begins with the deposition of a thin metal layer on the glass wafer. Micron-size windows, with desired designs, are then opened in the metallic layer thanks to a photolithography step and standard microelectronic equipments. A two-steps ion-exchange process is implemented to create the waveguides below to the glass surface. The first one consists in diffusing at high temperature silver ions into the glass wafer. The second step moves the waveguide deeper into the glass through the action of an external electric field.
The waveguide deep migration step can be localized on parts of the wafer and with dedicated equipments, Teem Photonics can provide post-processing shaping of the waveguide to locally taper the waveguide cross sectional shapes.