Post-fabrication trimming of photonic integrated circuits by local laser oxidation of titanium film

Local laser oxidation of a thin titanium film is considered as a means for achieving a precise adjustment of absorption coefficient and effective refractive index of dielectric optical waveguides. A fine phase tuning of an operating point and extinction ratio enhancement up to 57 dB were demonstrated on an integrated optical Ti:LiNbO3 Mach-Zehnder modulator. The technique affects only slightly the dielectric waveguide material and is very promising for a high accuracy permanent trimming of photonic devices based on dielectric waveguides of different material platforms and fabrication technologies.