Weak Probe Research Articles

Plasma local diagnostics by polarimetric method

We study the polarization plane rotation of weak probe signal in the field of strong electromagnetic waves in the presence of an external magnetic field of plasma, the polarization plane stimulated rotation angle of the probe signal in the intense laser field and in plasma is calculated. The estimates of the residual gas local density in a cesium plasma based on the effects of Faraday, Cotton–Mouton and stimulated rotation of the probe signal in the intense laser field have been found. It is shown, that the rotation angle in the cesium plasma medium has a complex structure.

Generation of optical -antisymmetry in a coherent N-type atomic medium

We have proposed two schemes to exhibit -antisymmetry in a four-level N-type atomic system interacting with two strong driving fields and a weak probe field. For both the schemes, the required spatially modulated coherence rendering -antisymmetry is achieved by employing a double-channel Gaussian beam for one driving field with a single channel for the other driving field in different field configurations. In each scheme, for equal and opposite detunings of the double-channel Gaussian beam, -antisymmetry can be obtained in the spatial domain. Such a way of control is unique to this model. Using the present method, it is possible to obtain -antisymmetry for both the homogeneously and inhomogeneously broadened atoms.

Manipulation of two dimensional atom microscopy by weak probe absorption spectrum

Manipulation of two dimensional atom microscopy by weak probe absorption spectrum

Orbital angular momentum induced asymmetric diffraction grating in quantum dot molecule

In this paper, we study the Fraunhofer diffraction pattern in a four-level quantum dot nanostructure. The quantum dot interacts with two weak probe and signal laser fields and two strong coupling lights where one of them is a two-dimensional standing wave field. We study the Fraunhofer diffraction pattern of the transmitted probe light when the coherent driving light becomes plan wave or Laguerre Gaussian (LG) vortex light. We found that by controlling the relative phase of the applied lights and orbital angular momentum (OAM) of LG light, the Fraunhofer diffraction pattern can be controlled and the probe energy transfer from zero order to the higher orders, respectively. Moreover, we realized that by controlling the OAM number of the vortex light the asymmetric diffraction pattern is possible.

Attosecond Monitoring of Nonadiabatic Molecular Dynamics by Transient X-ray Transmission Spectroscopy

Tracing the evolution of molecular coherences can provide a direct, unambiguous probe of nonadiabatic molecular processes, such as the passage through conical intersections of electronic states. Two techniques, attosecond transient absorption spectroscopy (ATAS) and Transient Redistribution of Ultrafast Electronic Coherences in Attosecond Raman Signals (TRUECARS), have been used or proposed for monitoring nonadiabatic molecular dynamics. Both techniques employ the transmission of a weak attosecond extreme-ultraviolet or X-ray probe to interrogate the molecule at controllable time delays with respect to an optical pump, thereby extracting dynamical information from transient spectral features. The connection between these techniques has not been firmly established yet. In this theoretical study, we provide a unified description of both transient transmission techniques, establishing their relationship as limits of the same pump-probe spectroscopy technique for different pulse parameter regimes. We demonstrate this by quantum dynamical simulations of thiophenol photodissociation and show how complementary coherence information can be revealed by the two techniques.

Diffraction grating via position dependent incident light in a closed-loop quantum system

We have proposed a new model for controlling the electromagnetically induced grating in a three-level closed-loop quantum system. The quantum system interacts with three-laser fields which one of them is the weak probe light and two of them are strong driving and coupling laser fields. These two strong laser fields have standing wave (SW) patterns in two x and y directions. This makes that the absorption and dispersion properties of the media change periodically which leads to diffraction of the transmitted light. We have shown that because of the closed-loop configuration of the quantum system the relative phase between applied lights can affect the diffraction grating pattern of the transmitted light. We have also discussed the Rabi-frequency effect of the driving and coupling lights on the different orders of the grating. We have shown that our proposed model may be used as a new tool for developing the future quantum information processing devices.

Revealing Local Temporal Profile of Laser Pulses of Intensity above 1014 W/cm2

We demonstrated a method for in situ temporal characterization of an intense femtosecond laser pulse around its focus where the laser intensity exceeds 1014 W/cm2. Our method is based on the second harmonic generation (SHG) by a relatively weak femtosecond probe pulse and the intense femtosecond pulses under analysis in the gas plasma. With the increase in the gas pressure, it was found that the incident pulse evolves from a Gaussian profile to a more complicated structure featured by multiple peaks in the temporal domain. Numerical simulations of filamentation propagation support the experimental observations of temporal evolution. This simple method can be applied to many situations involving femtosecond laser-gas interaction, when the temporal profile of the femtosecond pump laser pulse with an intensity above 1014 W/cm2 cannot be measured in traditional ways.

Quantum electrodynamics of non-demolition detection of single microwave photon by superconducting qubit array

By consistently applying the formalism of quantum electrodynamics, we developed a comprehensive theoretical framework describing the interaction of single microwave photons with an array of superconducting transmon qubits in a waveguide cavity resonator. In particular, we analyze the effects of microwave photons on the array’s response to a weak probe signal exciting the resonator. The study reveals that high quality factor cavities provide a better spectral resolution of the response, while cavities with moderate quality factors allow better sensitivity for a single-photon detection. Remarkably, our analysis showed that a single-photon signal can be detected by even a sole qubit in a cavity under the realistic range of system parameters. We also discuss how the quantum properties of the microwave radiation and electrodynamical properties of resonators affect the response of qubits’ array. Our results provide an efficient theoretical background for informing the development and design of quantum devices consisting of arrays of qubits, especially for those using a cavity where an explicit expression for the transmission or reflection is required.

Topological charge measurement in a four-level single layer graphene system

In this letter we have proposed a four-level graphene monolayer system for identifying the topological charge of Laguerre–Gaussian light. Here, we have shown that due to the four-wave mixing mechanism in the monolayer graphene system, a weak signal beam can be generated due to quantum coherence and interference effect. We have discussed the spatially dependent linear absorption spectrums of the weak probe and new generated signal beams via quantum mechanical density matrix formalism. We have found that by numbering the spot areas of the probe and signal beams, one can realize the topological charge of the Laguerre–Gaussian beam interacts by monolayer graphene system. Moreover, we have realized that for some topological charge the new generated signal beam can be amplified in the graphene system.

Shaped Microwave Field in a Three-Level Closed Loop Dense Atomic System.

In this work, we investigate the atomic properties of a three-level system under the effect of a shaped microwave field. The system is simultaneously driven by a powerful laser pulse and a weak constant probe that drives the ground state to an upper level. Meanwhile, an external microwave field drives the upper state to the middle transition with shaped waveforms. Hence, two situations are considered: one in which the atomic system is controlled by a strong laser pump and a classical constant microwave field, and another in which both the microwave and pump laser fields are shaped. Finally, for sake of comparison, we investigate the tanh-hyperbolic, the Gaussian and the power of the exponential microwave form in the system. Our results reveal that shaping the external microwave field has a significant impact on the absorption and dispersion coefficient dynamics. In comparison with the classical scenario, where usually the strong pump laser is considered to have a major role in controlling the absorption spectrum, we show that shaping the microwave field leads to distinct results.

Tunable Switching between Slow and Fast Light in the Graphene Nanodisks (GND)–Quantum Dot (QD) Plasmonic Hybrid Systems

Plasmonic nanocomposites demonstrate unique properties due to the plasmonic effects, especially those with graphene within their structures, thereby paving the way to various promising applications. In this paper, we investigate the linear properties of the graphene-nanodisks--quantum-dots hybrid plasmonic systems in the near-infrared region of the electromagnetic spectrum by numerically solving the linear susceptibility of the weak probe field at a steady state. Utilising the density matrix method under the weak probe field approximation, we derive the equations of motion for the density matrix elements using the dipole--dipole-interaction Hamiltonian under the rotating wave approximation, where the quantum dot is modelled as a three-level atomic system of Λ configuration interacting with two externally applied fields, a probe field, and a robust control field. We find that the linear response of our hybrid plasmonic system exhibits an electromagnetically induced transparency window and switching between absorption and amplification without population inversion in the vicinity of the resonance, which can be controlled by adjusting the parameters of the external fields and the system's setup. The probe field and the distance-adjustable major axis of the system must be aligned with the direction of the resonance energy of the hybrid system. Moreover, our plasmonic hybrid system offers tunable switching between slow and fast light near the resonance. Therefore, the linear properties obtained by the hybrid plasmonic system can be employed in applications such as communication, biosensing, plasmonic sensors, signal processing, optoelectronics, and photonic devices.

Dephasing of ultracold cesium 80D5/2-Rydberg electromagnetically induced transparency.

We study Rydberg electromagnetically induced transparency (EIT) of a cascade three-level atom involving 80D5/2 state in a strong interaction regime employing a cesium ultracold cloud. In our experiment, a strong coupling laser couples 6P3/2 to 80D5/2 transition, while a weak probe, driving 6S1/2 to 6P3/2 transition, probes the coupling induced EIT signal. At the two-photon resonance, we observe that the EIT transmission decreases slowly with time, which is a signature of interaction induced metastability. The dephasing rate γOD is extracted with optical depth OD = γODt. We find that the optical depth linearly increases with time at onset for a fixed probe incident photon number Rin before saturation. The dephasing rate shows a nonlinear dependence on Rin. The dephasing mechanism is mainly attributed to the strong dipole-dipole interactions, which leads to state transfer from nD5/2 to other Rydberg states. We demonstrate that the typical transfer time τ0(80D) obtained by the state selective field ionization technique is comparable with the decay time of EIT transmission τ0(EIT). The presented experiment provides a useful tool for investigating the strong nonlinear optical effects and metastable state in Rydberg many-body systems.

Two-dimensional electromagnetically induced grating via phase regulation in a closed-loop four-level atomic system

We proposed a theoretical scheme for two-dimensional (2D) electromagnetically induced grating (EIG) in a closed-loop four-level atomic system driven by a weak probe field, a traveling-wave control field, two orthogonal standing-wave fields and a microwave field. Due to low amplitude modulation accompanied with large phase modulation, EIG can be obtained and the probe energy can be diffracted into first-order and even high-order directions with high efficiency. The results show that the diffraction pattern and efficiency of the EIG could be adjusted effectively by the probe field detuning, the coherent field intensity, the interaction length. Meanwhile, the quantum interference between the amplitude modulation and phase modulation can be manipulated by the relative phase, which can be used to regulate the diffraction pattern and efficiency of the 2D EIG. Our scheme of 2D EIG may be useful in beam splitting and all-optical switching.

Vacuum birefringence at one-loop in a supercritical magnetic field superposed with a weak electric field and application to pulsar magnetosphere

Recent ultra-intense lasers of subcritical fields and proposed X-ray polarimetry for highly magnetized neutron stars of supercritical fields have attracted attention to vacuum birefringence, a unique feature of the nonlinear vacuum under strong electromagnetic fields. We propose a formulation of the vacuum birefringence in a strong magnetic field ({textbf{B}}) and a weak electric field ({textbf{E}}), including the effect of electromagnetic wrench (G equiv -{textbf{E}}cdot {textbf{B}}ne 0). To do so, we derive a closed expression of the one-loop effective Lagrangian for the combined magnetic and electric fields by using the formula of the one-loop effective Lagrangian for an arbitrarily strong magnetic field. We then employ the expression to derive the polarization and magnetization of the vacuum, from which we obtain the permittivity and permeability for a weak probe field. Specifically, we find the refractive indices and the associated polarization vectors of the probe field for the case of parallel magnetic and electric fields. The proposed formulation reproduces the known results for pure magnetic fields in the proper limit. Finally, we apply the formulation to the Goldreich–Julian pulsar model. Our formulation reveals the importance of the electromagnetic wrench in vacuum birefringence: it can reduce the difference between refractive indices and rotate polarization vectors to a significant degree. Such a quantitative understanding is crucial to the X-ray polarimetry for magnetized neutron stars or magnetars, which will demonstrate the fundamental feature of the strongly-modified quantum vacuum and estimate the extreme fields surrounding those astrophysical bodies.

Efficient diffraction control using a tunable active-Raman gain medium

We present a scheme to create an all-optical tunable and lossless waveguide using a controllable coherent Raman process in an atomic rubidium vapor in an $\mathcal{N}$-type configuration. We employ a Gaussian Raman field and a Laguerre-Gaussian control field to imprint a high-contrast tunable waveguidelike feature inside the atomic medium. We numerically demonstrate that such a waveguide is able to guide arbitrary modes of a weak probe beam to several Rayleigh lengths without diffraction and absorption. Our results on an all-optical waveguide-based scheme may have potential applications in lossless image processing, high-contrast biomedical imaging, and image metrology.

Experimental realization of a reconfigurable Lieb photonic lattice in a coherent atomic medium.

We have experimentally demonstrated the realization of an instantaneously reconfigurable Lieb photonic lattice with a flatband in a three-level Λ-type rubidium atomic configuration. Such a coherently controllable Lieb photonic lattice is optically induced by a coupling field possessing a spatially periodic intensity distribution (generated via a spatial light modulator) under the condition of electromagnetically induced transparency. The incident weak Gaussian probe field can experience discrete diffraction and the observed probe beam at the output surface of the medium exhibits the same Lieb pattern, verifying the formation of the refractive index with a Lieb profile inside the atomic vapor cell. The potential wells and the band structure of the Lieb photonic lattice can be effectively manipulated by easily tuning the frequency of the involved laser beams. The current work can promisingly pave the way for exploring the exotic dynamics as well as tunable photonic devices in Lieb photonic lattices.

Enhanced EIG in microwave controlled X-type atomic system

A microwave driven five-level X-type atomic system is proposed to diffract weak probe light into higher-order directions via the phenomenon of electromagnetically induced grating. In the proposed scheme, the effect of various system and field parameters on its higher-order diffraction efficiency is studied. The present atomic scheme offers excellent control over higher-order diffraction intensities by utilizing the microwave induced quantum interference effect. It is observed that the desired first-order diffraction efficiency can be attained through optimal selection of microwave field strength and relative phase factor.

Modulating optical vortices in an Airy beam by the electromagnetically induced transparency

We have introduced vortex fields in an Airy beam using interference between the lobes of the Airy beam, which is different from the previous method to generate optical vortices in an Airy beam. Compared to the interference of Gaussian beams, the vortex introduced by the interference between the Airy lobes is more robust due to the nondiffraction property of an Airy beam. The formation and disappearance of the vortex fields can be modulated by the electromagnetically induced transparency (EIT) effect and the probe field power. Specifically, no optical vortices are formed because interference between the lobes of an Airy beam cannot occur if there is a weak probe field. The EIT effect can control the generation and disappearance of the vortex field when the probe field power is critical. In the meantime, the vortex field changes the energy distribution in an Airy beam because of constructive and destructive interference in the main lobe and the side lobes. In particular, the EIT effect also can be used to regulate the position of the vortex phase singularity. We achieved Airy vortex beam regulation using multiparameters, which we believe can play a significant role in complex optical micromanipulation.

Pump-probe cavity optomechanics with a rotating atomic superfluid in a ring

Atomic superfluids confined in a ring provide a remarkable paradigm for quantized circulation. Very recently, a technique based on cavity optomechanics has been proposed [Kumar et al., Phys. Rev. Lett. 127, 113601 (2021)] for sensing and manipulating the rotation of a bosonic ring condensate with minimal destruction, in situ and in real time. Here, we theoretically investigate other coherent interference effects that can be supported by the proposed configuration. Specifically, in the presence of a strong control beam, we analyze the influence of atomic rotation on the transmission spectrum of a weak probe laser through a cavity containing a ring condensate. We present a detailed study of the resulting narrow probe transmission profiles and group delay and show that they can be tuned by means of persistent currents. Our results explore a facet of rotating matter waves and are relevant to applications such as atomtronics, sensing, and information processing.

Electromagnetically induced transparency with quantized fields in a dissipative optomechanical system

We study electromagnetically induced transparency (EIT) using quantized fields in a dissipative optomechanical system with two mechanical oscillators coupled to each other via the Coulomb interaction. The weak probe field is a finite bandwidth squeezed vacuum field. In the absence of the Coulomb coupling, we show that an EIT dip is observable in the homodyne spectrum of the output field even for the squeezed vacuum field at the single-photon level. We find that the thermal environment has a negative impact on the EIT behavior. In the presence of the Coulomb coupling, we show that double EIT dips appear in the homodyne spectrum of the output field. The separation between the two EIT dips can be used to measure the Coulomb coupling strength. Compared to the case of the purely dissipative coupling, the combined dispersive and dissipative coupling can make the EIT dip broader and the minimum value of the EIT dip smaller.