Post-process wavelength tuning of silicon photonic crystal slow-light waveguides

Silicon photonic crystal waveguides have enabled a range of technologies, yet their fabrication continues to present challenges. Here, we report on a post-processing method that allows us to tune the operational wavelength of slow-light photonic crystal waveguides in concert with optical characterization, offsetting the effects of hole-radii and slab thickness variations. Our method consist of wet chemical surface oxidation, followed by oxide stripping. Theoretical modelling shows that the changes in optical behavior were predictable, and hence controlled tuning can be achieved by changing the number of processing cycles, where each cycle removes approximately 0.25 nm from all exposed surfaces, producing a blueshift of 1.6±0.1  nm in operating wavelength.