Control of Bragg grating resonant wavelength through its dependence on the effective index of a waveguide

Fabrication tolerances for control of the Bragg wavelength of gratings in waveguides are studied. Techniques are demonstrated to hold the period of the grating constant to /spl plusmn/0.04 nm over the majority of the exposed wafer area, and ridge waveguides fabricated with standard thin film process equipment are found to have Bragg wavelengths constant to within /spl plusmn/0.2 nm. Additionally, adjacent ridges with differing widths are written in a single photomask/etch process step and found to controllably shift the Bragg wavelength over a 10-20-nm band suitable for a distributed Bragg reflector (DBR) laser array or a monolithic comb filter for wavelength division multiplexing (WDM) filtering/routing arrays.