a splitting that increases with decreasing barrier width. For barrier widths below 5 nm it exceeds the thermal energy at room temperature. For a given bairier width, we find only small variations of the tunneling induced splitting demonstrating agood homogeneitywithin a molecule ensemble.The entanglement may be controlled by application of electromagnetic field. For example, using an electric field along the molecule axis we can break the entanglement. Tunneling of carriers is prevented then and emission from intra-dot and inter-dot excitons in which electron and hole are located on the same and on opposite dots, respectively, is observed. The voltage required for the entanglement breaking increases with de^ creasing barrier width reflecting the increasing 'robustness'of the entanglement for narrow barriers.

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A resonator defined by mode-converting gratings in a waveguide is proposed This resonator can exhibit narrow resonances similar to Fabry-Perot with an advantage of being a fourport device capable of serving as an add-drop filter.