Abstract As early as 1917, Einstein had predicted that momentum is transferred in the absorption and emission of light, but it was not until the 1980's that such optical momentum transfer was used to cool and trap neutral atoms. By properly tuning laser light close to atomic transitions, atomic samples can be cooled to extremely low temperatures, the brightness of atomic beams can be enhanced to unprecedented values, and atoms can be manipulated with extraordinary precision. In this review several of the techniques for laser cooling and trapping of neutral atoms are described.

Cooling and trapping of neutral atoms

We have developed a theory for the two-photon fluorescence in nanohybrids made of an ensemble of metallic nanorod shells and an ensemble of quantum emitters. A metallic nanorod shell is made of a metallic rod and dielectric shell. We consider that the quantum emitters are four-level quantum systems. When a probe laser light falls on the metallic nanorod shells, the surface plasmon polariton electric field is produced at the interface between the metallic nanorod and dielectric shell. This electric field, along with the probe field, induces dipoles in the quantum emitters and nanorod shells. These dipoles interact with each other via the dipole–dipole interaction. The two-photon fluorescence has been calculated by using the quantum density matrix method in the presence of the dipole–dipole interaction (coupling). Analytical expressions of the two-photon fluorescence have been derived in the presence of the dipole–dipole interaction. We showed that that the two-photon process is made of two terms. The first term is the two-photon process due to the two probe field photons. On other the hand, the second term is made of one DDI field photon and one probe field photon. It is found that the surface plasmon polariton resonance energy is not resonant with the exciton energy, the two-photon fluorescence spectrum splits from one peak to three peaks. The splitting in the spectrum is due to the presence of the dressed states created in the system due to the strong dipole–dipole interaction. We also compared our theory with the experimental data of the metallic nanohybrid system made of metallic nanorod shells and quantum emitters (T790 molecules) and found a good agreement between the theory and the experiments.

Dipole–Dipole Interaction in Two-Photon Spectroscopy of Metallic Nanohybrids

We have developed a theory for the photoluminescence and absorption coefficient in nanohybrids made of an ensemble of metallic nanoparticles and the core–shell quantum emitter. The core–shell quantum emitter is made of a quantum emitter core and a dielectric shell. When a probe laser light falls on metallic nanoparticles, electric dipoles are induced in the ensemble. Hence, these dipoles interact with each other via the dipole–dipole interaction. The surface plasmon polaritons are also present in metallic nanoparticles. Excitons in the quantum emitter interact with these surface plasmon polaritons and the dipole–dipole interaction electric fields. Using the quantum mechanical density matrix method, we have developed a theory for the photoluminescence quenching and enhancement, the nonradiative decay rate, and the absorption coefficient for the quantum emitter in the ensemble of metallic nanoparticles. We showed that the nonradiative energy loss is mainly due to the exciton coupling with the dipole–dipole interaction and it is responsible for the power loss in the quantum emitter. This in turn produces anomalous photoluminescence enhancement and quenching. We have compared our theory with experimental data of core–shell CdSe/ZnS quantum dots embedded in an ensemble of Au nanoparticles. A good agreement between theory and experiment is found. We showed that there are an energy shift and an enhancement in the absorption peak due to the dipole–dipole interaction. Finally, we showed that there is the anomalous quenching and enhancement in the photoluminescence spectrum of the CdSe/ZnS quantum dot embedded in the ensemble of Au nanoparticles. This phenomenon also occurs mainly due to the dipole–dipole interaction in the ensemble of Au nanoparticles. These are interesting results and can be used to fabricate nanosensors for applications in nanomedicine and nanotechnology.

Anomalous Photoluminescence Quenching in Metallic Nanohybrids

Efficient two-dimensional atom localization in a five-level conductive chiral atomic medium via birefringence beam absorption spectrum

High-resolution two-dimensional atomic microscopy in a tripod-type four-level atomic medium via standing wave fields

We propose a flexible manipulation on the Goos-H\"anchen shift (GHS) via a cavity optomechanical system driven by an external coherent control field and reveal the behavior of the GHS as a result of light-matter interaction. It is achievable for both positive and negative GHSs in our system by tuning the coherent control field strength. The positive shift can flexibly be tuned to a negative shift by changing the cavity length. Furthermore, the control field can be used as a knob to turn the optical cavity on and off for manipulating the GHSs. A devastating suppression of the GHS can be observed due to weaker interaction between the cavity photons and the mechanical resonator by increasing the cavity decay rate. The results have potential applications in light-light manipulation via cavity optomechanical systems.

Flexible manipulation of the Goos-Hänchen shift in a cavity optomechanical system

We theoretically investigate the two-dimensional (2D) atomic localization via tunable surface plasmon polaritons (SPPs) in hybrid nanosystem that comprises an ensemble of metallic nanoparticles (MNPs) coupled to a coherent three-level λ -type atomic medium embedded as a dielectric host. Since the MNPs are shined with laser fields, the SPPs are generated at the interface between the MNPs and dielectric medium. The resonances of SPPs in the MNPs are calculated analytically by means of Maxwell’s equations under specific boundary conditions, whereas the dynamics of the atomic system are derived using the density matrix method. Owing to space-dependent light-matter interaction, the sharp localized peaks are observed in a single wavelength domain of 2D space with optimal probability. By optimizing the system parameters, ultrahigh-resolution and precision atomic localization can be achieved in a region smaller than λ / 30 × λ / 30 . The spatial resolution of atomic localization is efficiently improved compared to the previously studied cases. These results may have potential useful applications in the fields of quantum nanoplasmonics, nanomedicine, nanophotonics and nanotechnology.

Ultrahigh resolution two-dimensional atomic localization via tunable surface plasmon polaritons

The two-dimensional (2D) atomic localization is theoretically investigated via tunable surface plasmon polaritons (SPPs), generated on the metal (Ag) surface coupled to a quantum coherent three-level $$\lambda$$
 -type medium (
 $$^{87}$$
 Rb) embedded as a dielectric host. Such a useful scheme for highly precise atomic localization is reported by using the absorption spectrum of SPPs. Owing to space-dependent light–matter interaction, the sharp localized peaks are observed in a single wavelength domain of 2D space with maximum probability. By properly varying the system parameters, the precision and numbers of the localized peaks are controlled. Consequently, highly efficient and high-resolution atomic localization can be achieved in a region smaller than $$\lambda /20\times \lambda /20$$
 . The spatial resolution of atomic localization is greatly improved as compared to the previously studied cases. These results may have potential useful applications in the fields of quantum nanoplasmonics, nanolithography, and nanophotonics.

https://link.springer.com/content/pdf/10.1007/s11468-021-01404-x.pdf

Muhib Ullah

Papers

High-resolution two-dimensional atomic microscopy in a tripod-type four-level atomic medium via standing wave fields

Flexible manipulation of the Goos-Hänchen shift in a cavity optomechanical system

Ultrahigh resolution two-dimensional atomic localization via tunable surface plasmon polaritons

High-Resolution Two-Dimensional Atomic Localization Via Tunable Surface Plasmon Polaritons

Four‐Wave Mixing Response via Hybrid Coulomb‐Coupled Cavity Optomechanics