Gain-assisted enhanced rotary and lateral photon drags in bidirectionally rotating chiral nanostructures

Abstract

This study presents a theoretical investigation of the gain-assisted rotary and lateral photon drag effects induced by bidirectional rotation in chiral nanostructures composed of laterally coupled CdSe/ZnS semiconductor double quantum dot molecules. The system is driven by a combination of probe and control electromagnetic fields, where electron tunneling strength plays a pivotal role in shaping the optical, chiral, and gain-assisted responses. The chiral medium exhibits strong magnetoelectric coupling and structural asymmetry, enabling dynamic control over the rotary and lateral photon drag effects for both left- and right-circularly polarized (LCP and RCP) beams. Notably, the bidirectional rotation of the chiral nanostructure significantly enhances the drag response, with the degree of enhancement being strongly dependent on the tunneling strength. A large negative group index is observed, particularly for the RCP beam, indicating the presence of anomalous dispersion, medium gain, and high sensitivity to rotational dynamics. Additionally, the lateral photon drag demonstrates tunable beam displacement under varying tunneling strengths, offering an additional degree of control in light manipulation. Furthermore, the divergence angle between LCP and RCP beams, as well as the group indices, are shown to vary with the phase of the control field and magnetic field detuning. The electric and magnetic susceptibilities, along with the chiral coefficients, reveal enhanced dispersion and reduced absorption (even showing gain) at higher tunneling strengths. These results highlight the critical role of chirality, tunneling, gain, and rotational control in modulating light-matter interactions and pave the way for practical applications in lateral beam steering, optical communication, polarization encoding, optical tweezers, and chiral sensing technologies.