Two-dimensional asymmetric diffraction induced by vortex light in quantum-dot-molecule systems under spontaneously generated coherence

Quantum dot molecules (QDMs), with their unique optoelectronic properties derived from quantum confinement and tunneling effects, are not only promising for advanced photonic applications but also provide the intrinsic advantage of nanoscale dimensions, which is critical for integrated miniaturized devices. In this work, we propose a scheme to realize a high-intensity two-dimensional asymmetric electromagnetically induced diffraction grating in a QDMs system by incorporating spontaneously generated coherence (SGC) and dual tunneling channels. Our theoretical analysis shows that the presence of SGC markedly enhances the intensity and efficiency of higher-order diffractions. Furthermore, by adjusting the orbital angular momentum and beam waist of vortex beams, we not only amplify the disparity in asymmetric diffraction and enhance the efficiency of the third-order diffraction peak, but also enable a lossless spatial interchange between the diffraction peak positions and those at symmetric positions solely by reversing the orbital angular momentum direction. Additionally, tuning the interdot tunneling strength increases the maximum third-order diffraction intensity by three orders of magnitude, reaching an intensity that is more than ten times higher than the third-order diffraction intensity observed at symmetric positions. These results, which fully leverage the nanoscale advantage and tunable characteristics of QDMs, offer a solid foundation for the implementation of compact photonic devices and pave the way for potential applications in optical diffractive neural networks and electromagnetically induced quantum holography.