Patent ID: 7294454

Claim:
A method of writing a waveguide having a bend, a splitter, or a coupler structure and having a waveguide propagation axis in a substrate, the method comprising the steps of: directing an ultrashort laser beam to the substrate in transverse relation to the waveguide propagation axis to generate an ultrashort laser pulse focus in the substrate; modifying a refractive index in an affected region in the substrate along the waveguide propagation axis via the ultrashort laser pulse focus; adjusting polarization of the ultrashort laser beam during the directing step to maintain the polarization relative to the waveguide propagation axis; and moving the ultrashort laser pulse focus in a direction other than the waveguide propagation axis to generate a widened affected region along the waveguide propagation axis; wherein— the widened affected region has a cross-sectional profile capable of supporting a fundamental mode of a signal having a telecommunications infrared (TIR) wavelength, and the affected region has a cross-sectional profile incapable of supporting the fundamental mode of the signal having the TIR wavelength.