Molybdenum Nanosheets-Engineered CuO Waveguides for Broadband Optical and Microwave-Frequency Control

Herein, CuO waveguides are deposited on glass substrates and then overlaid with ultrathin Mo nanosheets (50–300 nm thick) to modify their electro-optical and microwave properties. Although the Mo thickness does not modify the microstructure, it systematically increases the surface roughness, optical absorption, band tail states, and optical bandgap. The addition of Mo facilitates the controlled modification of dielectric screening, optical losses, and carrier transport mechanisms for both visible and near-infrared wavelengths. Moreover, the drastic increment in the cutoff frequency to 25 THz at 406 nm (laser lines) underlies the enhanced high-speed optoelectronics provided by the Mo-modified waveguides. When incorporated into a periodic CuO waveguide device with platinum (Pt) top electrodes, the ultrathin Mo coatings further modify the microwave properties. Specifically, the 100 nm Mo-coated waveguide shows a strong reflection minimum at −32 dB and an effective working band of 2.40 at 3–5 GHz. Simultaneously, the complementary S₂₁ transmission characteristics show smooth and broad incrementing transmission efficiencies for increased Mo thickness, thereby confirming the controlled coupling efficacy of the CuO/Mo/Pt waveguides. The Mo-modified copper oxide waveguides demonstrated here underlie their suitability as tunable platforms for the development of various optoelectronics and terahertz applications.