Phonon-Assisted Electro-Optical Switches and Logic Gates Based on Semiconductor Nanostructures.

High-performance nanostructured electro-optical switches and logic gates are highly desirable as essential building blocks in integrated photonics. In contrast to silicon-based optoelectronic devices, with their inherent indirect optical bandgap, weak light-modulation mechanism, and sophisticated device configuration, direct-bandgap-semiconductor nanostructures with attractive electro-optical properties are promising candidates for the construction of nanoscale optical switches for on-chip photonic integrations. However, previously reported semiconductor-nanostructure optical switches suffer from serious drawbacks such as high drive voltage, limited operation spectral range, and low modulation depth. High-efficiency electro-optical switches based on single CdS nanobelts with low drive voltage, ultra-high on/off ratio, and broad operation wavelength range, properties resulting from unique electric-field-dependent phonon-assisted optical transitions, are demonstrated. Furthermore, functional NOT, NOR, and NAND optical logic gates are demonstrated based on these switches. These switches and optical logic gates represent an important step toward integrated photonic circuits.