An optical modulator for switching an optical signal of wavelength from one waveguide-electrode to another requires that both waveguide-electrodes be made of an electrically conducting material. Also, a non-conducting cross-coupling material fills a slot along a length L between the waveguide-electrodes. Importantly, cross-coupling material in the slot provides a separation distance x.sub.c between the waveguide-electrodes that is less than 0.35 microns. When a switching voltage V.sub. is selectively applied to the waveguide-electrodes, a strong uniform electric field E is created within the cross-coupling material. Thus, E modulates the cross-coupling length of the optical signal by an increment each time it passes back and forth through the cross-coupling material along the length L. Thus, after an N number of cross-coupling length cycles along the length L, when N equals one cross-coupling length, the optical signal is switched from one waveguide-electrode to the other.

An electro-optically coupled switch includes first and second waveguides which are aligned in parallel to each other, with a thin, flat layer of cross-coupling material sandwiched therebetween. A voltage source is provided to establish a strong uniform electric field that is oriented perpendicular across the entire layer of cross-coupling material between the waveguides. Incorporated with the voltage source is a switch for changing the electric field, to thereby alter the refractive index of the cross-coupling material for transferring the transmission of an optical signal from one waveguide to the other.

An optical coupler includes a first waveguide including a first multi-mode waveguide section having a cross-section characterized by a first height and a first width that is greater than the first height and a second waveguide including a second multi-mode waveguide section having a cross-section characterized by a second height and a second width that is greater than the second height. The first multi-mode waveguide section is positioned adjacent to the second multi-mode waveguide section at least partially above or below the second multi-mode waveguide so that light entering the first multi-mode waveguide section is coupled from the first multi-mode waveguide section to the second multi-mode waveguide section. Methods for coupling light between waveguides with the optical coupler and optical devices that include the optical coupler are also described.

An electronic device is provided. The electronic device includes a plurality of electronic components, a plurality of first waveguides, and a switch element. The first waveguides are disposed under the electronic components. The switch element is disposed under the electronic components and at an elevation different from the first waveguides, wherein the switch element is configured to optically connect a first one of the first waveguides to a second one of the first waveguides.