Rare-earth-doped lithium niobate waveguide structures
AssigneePirelli Cavi S.p.A.
InventorsWolfgang Sohler, Hubertus Suche
Life of this patent
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Abstract
In a waveguide structure with diffused rare-earth doping in a light channel arranged lithium niobate crystal surface, the rare-earth doping is arranged in an effective rare-earth doping region approximately coaxially with the light guide channel; the light guide channel is diffused directly frown the crystal surface and its expansion is laterally limited.
Claims24
Waveguide structure having diffused rare-earth doping in a light-guide channel (LK) arranged in a lithium niobate crystal surface (S), characterized in that the rare-earth doping is disposed in an effective rare-earth doping region (SE) approximately coaxially with the light-guide channel (LK), said doping region (SE) having been diffused directly from the crystal surface (S) and, having effective boundaries (W, TS) that are less laterally and depthwise than that of the light-guide channel (LK), at the crystal surface (S) the rare-earth doping is of a lower concentration (CS) than at the centre (Z) of the light-guide channel (LK), and the rare earth is erbium.
Waveguide structure according to one of the preceding claims, characterised in that its light-guide channel (LK) is an optical travelling-wave amplifier (WV), at the entrance side of which an input light wave (EL) for amplification is to be applied and to which a pump light wave is supplied via a pump wave entrance (PE) and from the exit side of which the input light wave (EL) emerges directly as an amplified output light wave (AL), or emerges through a wavelength-selective mirror (DM) which reflects the pump light wave into the travelling-wave amplifier region, with the result that said pump light wave also amplifies the input light wave (EL) in the reverse direction.
Method of manufacturing a waveguide structure in which rare-earth doping is introduced into a lithium niobate crystal (K) by tempering into a rare-earth doping region (SE) of preset depth (TS) below a crystal surface (S), after which a light-guide channel (LK) is produced by titanium diffusion or proton exchange in the rare-earth doping region (SE), characterised in that the rare earth is applied as a metal or oxide layer (SS) onto the crystal surface (S) and thereafter a first tempering step (I) is performed at a temperature above 1000.degree. C. in an AR/O.sub.2 atmosphere, with depth-oriented rare-earth diffusion taking place, after which the crystal surface (S) is coated with a sol gel (SG), after which in a second tempering step (II) the rare-earth doping is diffused close to the surface, thereby producing a lower rare-earth concentration (CS) at the surface than deeper down, after which the sol gel (SG) is etched away.
Dependencies are inferred from the claim text.