Use of the Laguerre-Gaussian fields in an atom-light interaction makes the linewidth of the optical spectrum narrow. We exploit this fact for providing the ability to accomplish simultaneous ultra-high precision and spatial resolution atom localization in a double-Λ atomic system; Under multi-photon resonance condition, the resolution of the localization is remarkably improved so that the atom can be localized in a region smaller than λ/20 × λ/20. Most prominently, the probability of finding the atom at a particular position is always 100%, when a photon with certain frequencies is absorbed or amplified. Such features are mainly dependent on radial dependence associated with the Laguerre-Gaussian fields in a spatially dependent atom-light interaction.

We present a convenient way to obtain an optical power limiting behavior in a quantum dot molecule system, induced by an interdot tunneling. Also, the effect of system parameters on the limiting performance is investigated; interestingly, the tunneling rate can affect the limiting performance of the system so that the threshold of the limiting behavior can be a function of the input voltage, allowing the optimization of the limiting action. Furthermore, by investigating the absorption of the probe field, it is demonstrated that the optical limiting is due to a reverse saturable absorption mechanism; indeed, analytical results show that this mechanism is based on a cross-Kerr optical nonlinearity induced by the tunneling. Additionally, the limiting properties of the system are studied by using a Z-scan technique.

Generation and control of the reverse saturable absorption (RSA) and optical limiting (OL) are investigated in a four-level Y-type quantum system. It is demonstrated that the applied laser fields induce the RSA and it can be coherently controlled by either intensity or frequency of the applied laser fields. The effect of the static magnetic field on the induced RSA is studied and we obtain that it has a constructive role in determining the intensity range in which the OL is established in the system. In addition, we find that the transmission of the suggested optical limiter can be decreased either by increasing the length of the medium or by getting the atomic system denser. Finally, the Z-scan technique is presented to confirm our theoretical results. The proposed scheme can be used in designing the coherent optical limiters with controllable threshold and intensity range of the OL.

By presenting a theoretical steady-state rate equation analysis, we demonstrate an efficient optical power limiting in a fullerene system, which can be attributed to a reverse saturable absorption mechanism. The limiting behavior, characterized by means of the sample’s transmittance, is explained via the population redistribution among singlet and triplet levels. In addition, the effects of intersystem crossing and reverse intersystem crossing rates on the limiting behavior are investigated. Our numerical results show how these rates alter the optical limiting performance; indeed, the intersystem crossing has a constructive role in decreasing the optical limiting threshold. In addition, a theoretical investigation of the z-scan technique is employed to further characterize the power limiting properties.

We study the generation and control of the microwave (MW)-induced reverse saturable absorption (RSA) and optical limiting (OL) in a three-level pump-probe V-type quantum system. It is shown that the saturable absorption switches to the RSA by applying the MW field to the transition between two upper levels. Moreover, it is demonstrated that the RSA and the induced OL threshold are controlled by either the intensity or detuning of the MW field. In addition, the effect of the coupling field on the induced optical limiting is studied, and it is obtained that the cross-Kerr nonlinearity has a major role in establishing efficient optical power limiting. In addition, we demonstrate that an increase in the atomic density and length of the medium makes the optical limiter more powerful. Finally, the theoretical Z-scan technique is presented to confirm the obtained results of the microwave-induced OL. The proposed scheme can be used to prepare a controllable optical limiter with various thresholds, which can protect the optical devices with different sensitivities.