Overlapping Ridge Waveguide Modulator for Compact High-Speed Modulation

The patent transitions from planar waveguide structures to three-dimensional stacked waveguide configurations with vertical coupling. By utilizing the vertical dimension through multiple waveguide layers separated by dielectric materials, the optical interaction length is effectively increased without proportionally increasing the device footprint, thereby achieving high modulation depth in a compact form factor suitable for integrated circuits

The patent implements nested waveguide structures where multiple waveguide layers are stacked vertically with dielectric materials filling the spaces between them. This nested configuration allows multiple optical interaction paths to be contained within a compact vertical space, achieving enhanced modulation depth while maintaining small device dimensions and high integration density

The patent introduces dielectric materials as intermediaries between the waveguide cores and the driving electrodes. These dielectric layers act as electrical insulators that prevent direct contact and reduce current density in the waveguide regions, thereby minimizing Joule heating and thermo-optic effects while still enabling effective electro-optic modulation through capacitive coupling

The patent replaces direct current-driven carrier injection mechanisms with capacitive coupling through dielectric layers. Instead of using high current densities to directly inject carriers into the waveguide, the system uses voltage applied across dielectric layers to modulate the refractive index through fringe field effects, substituting a mechanical/electrical injection approach with an electrostatic field-based approach that reduces heating