US Patent 10185205 CMOS compatible optical modulators

Ring modulators based on interdigitated junctions may be driven in full or partial standing wave mode and, active regions (providing the modulation) and light-absorptive regions (e.g. providing electrical conduction) are placed in a pattern inside a resonant cavity in order to match the maxima and minima of the optical field, respectively. The pattern may be periodic to match the periodicity of a typical electromagnetic field which is periodic with the wavelength. It may also be aperiodic in the case that the cross-section or materials are engineered along the direction of propagation such that the propagation constant (and thus wavelength, i.e. optical wave “local periodicity”) change along the propagation direction.