Low-Frequency Optical Response, Gain-Assisted Photon Superluminal Propagation, and Optical Drag in a Transparent Conductor Oxide (GZO)

Superluminal propagation of light in various materials has attracted tremendous research for fundamental and practical interest. This study is aimed at investigating the low-frequency off-resonance optical response, gain-assisted superluminal photon propagation, and optical drag through GaZnO, an innovative TCO (transparent conductor oxide) material. TCO materials are among the novel class of optical materials, simultaneously showing high transparency and conductivity, leading to milestone fundamental and practical device implications. Earlier, no study reported superluminal propagation of light and rotary photon drag in GaZnO in the low-frequency range. In particular, gain-assisted superluminal propagation of light and photon drag is studied employing the Drude-Lorentz model. The phenomenon of gain-assisted superluminal propagation is studied in light of negative/positive refractive index and group index that lead to superluminal phase velocity and group velocity. TCO nature of GaZnO is also justified in light of large absorption coefficient and real conductivity at the highest transmission coefficient. The findings may leads to potential applications in the advanced applications in laser and optics, photonics, optical communication systems, signal processing, and quantum information processing.