Abstract

Highly functional Planar Lightwave Circuits (PLC) can be designed using silica-on-silicon waveguide technology,¹ and the possibility of writing Bragg gratings in such waveguides further enhances their potential uses.² Strong Bragg gratings photoinduced in planar silica-on-silicon waveguides with a germanium-doped core are usually obtained by high pressure hydrogen loading of the glass prior to exposure.²,³ In the work presented here we demonstrate that hydrogen loading is not necessary when high intensity light at 193 nm from an ArF laser is used to produce the index change, an effect originally observed in germanium-doped optical fibers.⁴,⁵ The waveguides used are standard PLCs with a core index difference (Δ) of 0.75% (commercially available) and 1%.¹ One drawback of silica-on-silicon waveguides is their small strain birefringence.⁶,⁷ We show here that there is a sizeable birefringence in the ArF laser-induced average index change that is large enough and of the proper sign to compensate for the initial waveguide birefringence. For demonstration, 4 mm-long Bragg grating filters with more than 30 dB of transmission loss at the Bragg wavelength are presented.

© 1997 Optical Society of America