Group-index engineering in silicon corrugated waveguides.

We demonstrate group-index engineering in a one-dimensional periodic silicon structure consisting of a deep-etched laterally corrugated waveguide with circular holes patterned onto its wide section. Our theoretical analysis, supported by experimental results, shows that the first-order optical mode can propagate inside the Brillouin zone with a relatively high group index over a wide frequency range. Nearly constant group index as high as 13.5 over a wavelength range of approximately 14 nm is experimentally demonstrated in a 50-microm-long waveguide.