Second-order nonlinear susceptibility (SONS) in a ladder-plus-Y double quantum dot structure was modeled and then studied numerically under the application of an electric field. The density matrix theory was used to formulate the system while the orthogonalized plane waves for wetting layer-quantum dot (WL-QD) were considered to state the momentum matrix elements for this system. It is found that the momenta follow the smallest energy difference between states with an obvious overlap of the mediated states. Since WL-QD momenta are small, neglecting WL gives high SONS. Millimeter waves are predicted, and a huge SONS can be obtained by the application of more optical fields, which is important in medical and biological applications. The possibility of changing light speed between subluminal and superluminal was predicted here. This opens the way for many applications like multichannel waveguide-multichannel quantum information processing, real quality imaging, and temporal clock.

This work proposes the double quantum dot (DQD)-metal nanoparticle (MNP) hybrid system for a high energy absorption rate. The structure is modeled using density matrix equations that consider the interaction between excitons and surface plasmons. The wetting layer (WL)-DQD transitions are considered, and the orthogonalized plane wave (OPW) between these transitions is considered. The DQD energy states and momentum calculations with OPW are the figure of merit recognizing this DQD-MNP work. The results show that at the high pump and probe application, the total absorption rate $$({Q}_{tot})$$ ( Q tot ) of the DQD-MNP hybrid system is increased by reducing the distance between DQD-MNP. The high $${Q}_{tot}$$ Q tot obtained may relate to two reasons: first, the WL washes out modes other than the condensated main mode. Second, the high flexibility of manipulating DQD states compared to QD states results in more optical properties for DQD. The $${Q}_{DQD}$$ Q DQD is increased at a small MNP radius on the contrary to the $${Q}_{MNP}$$ Q MNP which is increased at a wider MNP radius. Under high tunneling, a broader blue shift in the $${Q}_{tot}$$ Q tot due to the destructive interference between fields is seen and the synchronization between $${Q}_{MNP}$$ Q MNP and $${Q}_{DQD}$$ Q DQD is destroyed. $${Q}_{tot}$$ Q tot for the DQD-MNP is increased by six orders while $${Q}_{DQD}$$ Q DQD is by eight orders compared to the single QD-MNP hybrid system. The high absorption rate of the DQD-MNP hybrid system comes from the transition possibilities and flexibility of choosing the transitions in the DQD system, which strengthens the transitions and increases the linear and nonlinear optical properties. This will make the DQD-MNP hybrid systems preferable to QD-MNP systems.

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Nanomaterials are at the forefront of the fast-paced development of nanotechnology. These materials are outstanding and indispensable in various human activities as long as their size-dependent characteristics. One of the most promising applications of nanomaterials is biomedical. This work reviews the hybrid quantum dot-metal nanoparticle applications in biomedical. An analytical model for the double quantum dot–metal nanoparticle system is proposed, and the system susceptibility is calculated.

This work uses the Green function to model the emission spectra from a hybrid metal nanoparticle (MNP) coupled with a double quantum dot (DQD), considering higher-order plasmonic mode contribution. It calculates the quantum dot (QD) energy states and momenta, i.e., this work differs from other strong-coupling systems by considering the material entities. A Fano-shape spectrum is shown with peaks depending on interference between the fields with the DQD and MNP. A prominent effect of the pump field appears as it interferes with other fields (probe and MNP polarization field). The MNP–DQD distance and MNP radius control the peak height and its position in the spectrum. The importance of the probe field in controlling the peak frequency and its height is demonstrated. The transition energy with momenta controls the spectra. An approximated relation is presented. High strength in the DQD–MNP and a more strong contribution are obtained compared to QD–MNP.