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

In this paper, we present a new graphene plasmonic sensing structure and use the finite difference time domain method and also a graphene superconducting properties for counting the number of n-graphene layer, where 1 ≤ n ≤ 5. From the intensity change of the reflection of graphene plasmons excited at the boundary of graphene/white graphene layer, we can exactly estimate the number of graphene layers. The structure considered here supports surface plasmons whose dispersion properties can be harnessed by applying an electrical field to the graphene. By utilizing this feature, efficient coupling of the incident light to the surface plasmons of the structure is used for counting the number of graphene layer. Therefore, single layer graphene can be distinguished from double- and few-layer by efficient coupling condition. Also, the effects of the substrate of graphene on the reflection of the transverse electric and magnetic graphene plasmons are investigated. By applying a chemical potential of v g = 0.4 eV, a compact sensor with the footprint of 0.6 nm × 10 μ m × 20 μ m is achieved. Finally, experimental setup is used to verify and validate this numerical model with good results.

Graphene sensing nanostructure for exact graphene layers identification at terahertz frequency

We show that it is possible to change from a {\it subnatural} electromagnetically induced transparency (EIT) feature to a {\it subnatural} electromagnetically induced absorption (EIA) feature in a (degenerate) three-level $\Lambda$ system. The change is effected by turning on a second control beam counter-propagating with respect to the first beam. We observe this change in the $D_2$ line of Rb in a room-temperature vapor cell. The observations are supported by density-matrix analysis of the complete sublevel structure including the effect of Doppler averaging, but can be understood qualitatively as arising due to the formation of $N$-type systems with the two control beams. Since many of the applications of EIT and EIA rely on the anomalous dispersion near the resonances, this introduces a new ability to control the sign of the dispersion.

Conversion between electromagnetically induced transparency and absorption in a three-level lambda system

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

https://iopscience.iop.org/article/10.1088/1402-4896/aba055/pdf

Optical soliton through induced cesium doppler broadening medium

The control and modification of divergence angle and birefringent rotary photon drags under the effect of quantum tunnelling is investigated in this article. The circularly birefringence Δn=nr(+)−nr(−) , divergence angle θ d and rotary photon dragging angles θr(±) are found to have modified with the strength of tunnelling frequencies. The left and right circularly polarized beams show superlominality of group velocities −c/150 and −c/50, respectively, and the divergence angle of 0.050 radian per increment of tunnelling frequency. The maximum of rotary photon drags for both beams is measured θr(±)=±2 micro radian with fractional change of 2%. The output pulses intensities ∣Eout+(t)∣2 and ∣Eout−(t)∣2 show uniform undistorted shapes with tunnelling frequencies and no energy losses. The results could have significant applications in the fields of quantum optics, photonics, plasmonics and special mode imaging coding technology.

Tunnelling based birefringent rotary photon dragging through induced chiral medium

Herein, we propose a scheme for the realization of two-dimensional atomic localization in a λ-type three-level atomic medium such that the atom interacts with the two orthogonal standing-wave fields and a probe field. Because of the spatially dependent atom-field interaction, the information about the position of the atom can be obtained by monitoring the probe transmission spectra of the weak probe field for the first time. A single and double sharp localized peaks are observed in the one-wavelength domain. We have theoretically archived high-resolution and high-precision atomic localization within a region smaller than λ/25 × λ/25. The results may have potential applications in the field of nano-lithography and advance laser cooling technology.

https://iopscience.iop.org/article/10.1088/1572-9494/abe229/pdf

Bakth Amin Bacha

Papers

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

Optical soliton through induced cesium doppler broadening medium

Tunnelling based birefringent rotary photon dragging through induced chiral medium

Spatial-dependent probe transmission based high-precision two-dimensional atomic localization