High bandwidth (e.g., > 100 GHz) modulators and methods of fabricating such are provided. An EAM comprises a waveguide mesa comprising a continuous multi-quantum well (MQW) layer; a plurality of electrode segments disposed on the waveguide mesa; and a microstrip transmission line disposed on an insulating material layer and in electrical communication with the plurality of electrode segments via conducting bridges. The waveguide mesa comprises alternating active sections and passive sections. An electrode segment of the plurality of electrodes is disposed on a respective one of the active sections. Portions of the continuous MQW layer disposed in each of the active sections having an energy gap defining an active energy gap value. Portions of the continuous MQW layer disposed in each of the passive sections having an energy gap defining an passive energy gap value. The active energy gap value is less than the passive energy gap value.

An optical cavity device has two spaced-apart multiple quantum well (MQW) regions, a central electrode terminal and two marginal electrode terminals. The central electrode terminal contacts a central electrode layer between the MQW regions, and each marginal electrode terminal contacts a separate marginal electrode layer on the other side of each MQW region. There are also two mirrors outside of the MQW regions, forming the cavity. The device has a less-absorptive state and a more-absorptive state selected by varying the voltage between the anode and at least one of the two cathodes. The two marginal electrode terminals may be electrically connected, or the voltage between the central electrode terminal and the marginal electrode terminals may be varied independently. These devices may form an array of detectors, modulators or both. In an array, multiple devices may share a common electrode layer. Devices may be stacked, with two or more anode terminals and two more cathode terminals alternating in the stack. Three or more MQW regions are then formed with either an anode layer or a cathode layer between each MQW region.

Two-dimensional (2D) crystals have renewed opportunities in artificial lattice design and assembly without the constraints of epitaxy. However, the lack of thickness control in exfoliated van der Waals (vdW) layers prevents realization of repeat units with high fidelity. Uniform, wafer-scale samples permits engineering of both electronic and optical dispersions in stacks of disparate 2D layers with multiple repeating units. Systems, methods, and devices present optical dispersion engineering in a superlattice structure including alternating layers of 2D excitonic chalcogenides and dielectric insulators. Examples demonstrate >90% narrowband absorption in <4 nm active layer excitonic absorber medium at room temperature, concurrently with enhanced photoluminescence in cm.sup.2 samples. These superlattices show evidence of strong light-matter coupling and exciton-polariton formation with geometry-tunable coupling constants. The results demonstrate proof of concept structures with engineered optical properties and pave the way for a broad class of scalable, designer optical metamaterials from atomically-thin layers.