| 摘要 |
Transmission characteristics of an optical device 200, fabricated from multiple layers 16, 27, 28 of silica-based glass on a silicon substrate 26, are modified by localized thermal treatment. The beam 501 of a carbon-dioxide (CO2) laser 510 is used to selectively soften the core and/or cladding material of a waveguide structure during or after the fabrication process. In one application, softening relieves the strain developed between the waveguide structure and the silicon substrate and substantially reduces or eliminates birefringence. In a second application, the CO2 laser is operated at another power level in order to modify the index of refraction. Changes in the index of refraction change the speed of light through a waveguide thereby changing the phase shift associated with the waveguide. In a third application, the CO2 laser is operated at yet another power level to increase the transmission loss of the waveguide. In all of the embodiments, heat treatment is substantially faster and/or less expensive than known techniques for modifying the transmission characteristics of an optical device. <IMAGE> |
