Spontaneously Generated Coherence Research Articles

Gain-assisted quantum heat engine based on electromagnetically induced transparency

We propose a scheme to realize a gain-assisted quantum heat engine (QHE) based on electromagnetically induced transparency (EIT), which consists of a three-level Λ-type atomic system interacting with two thermal reservoirs and a coupling field. The gain without inversion is induced to the system via spontaneously generated coherence (SGC) between two lower levels. The SGC has significantly affect on the system’s dynamics, resulting in an enhancement of the emission cross-section and spectral brightness of the QHE.

Controlling behaviour of transparency and absorption in three-coupled multiple quantum wells via spontaneously generated coherence

This article presents a coherent phenomenon called spontaneously generated coherence (SGC) under the regime of electromagnetically induced transparency (EIT) in a three-coupled multiple quantum wells. We demonstrate that the presence of SGC in these quantum wells lead to intriguing modifications in the transparency window within the absorption spectrum. At the same time, modification of the dispersive nature is also demonstrated which enables the feasibility of the system in diverse applications based on light propagation. The absorption and dispersion responses are found to be varied by the individual strength of the first and second control fields in presence as well as in absence of SGC in the EIT regime. The positional shifting of the transparency window and simultaneous modifications in the dispersive profiles by tuning the control field detunings of both the first and second control fields are also revealed. Some absorption and dispersion contours are illustrated for getting better insights into the modifications of the optical responses via SGC. Finally, by manipulating the strength of the SGC parameter, we observe the changes in the respective position of the transparency window and dispersion curve. It is expected that the current investigations will pave novel ways for innovative applications in quantum communications, and fabrication of advanced photonic devices.

Colossal Kerr nonlinearity without absorption in a five-level atomic medium

In this work, we present an analytical method to achieve giant Kerr nonlinearity without absorption in a five-level atomic medium. By using iterative perturbation technique on density matrix equations, we have derived the analytical expressions of nonlinear susceptibility and Kerr nonlinear coefficient in the presence of spontaneously generated coherence (SGC) and relative phase between applied laser fields. It shows that, this five-level atomic medium exhibits multiple electromagnetically induced transparency (EIT) at three different frequencies, at the same time, the Kerr nonlinear coefficient is enhanced around three transparent spectral regions; in each such EIT region appears a pair of positive–negative peaks of Kerr nonlinear coefficient. In particular, these nonlinear peaks are moved to the center of the EIT windows via SGC. This means that the Kerr nonlinear coefficient is enhanced with completely suppressed absorption at different transparency frequencies. Furthermore, the magnitude and the sign of the Kerr nonlinear coefficient are easily controlled according to the SGC strength, the coupling laser intensity, and the relative phase between applied laser fields. Such a giant nonlinear medium can be useful for photonic devices working in the resonant frequency region without absorption. As a typical application, this giant Kerr nonlinear material has been applied to an interferometer for the formation of optical bistability, and showed the appearance of OB at the resonant frequency with significantly reduced threshold intensity and OB width.

ẢNH HƯỞNG CỦA ĐỘ KẾT HỢP ĐƯỢC TẠO BỞI PHÁT XẠ TỰ PHÁT VÀ BƠM KHÔNG KẾT HỢP LÊN CHUYỂN MẠCH TOÀN QUANG TRONG MÔI TRƯỜNG NGUYÊN TỬ BA MỨC BẬC THANG KHI CÓ MẶT CỦA PHA TƯƠNG ĐỐI

This paper investigates the impact of spontaneously generated coherence (SGC) and relative phase on the propagation of a probe laser pulse in the presence of an incoherent pump field. It was discovered that when the control laser field is turned on, the medium forms an electromagnetically induced transparency (EIT) effect. Hence, the propagation of the probe laser pulse has a like-soliton form/shape. On the contrary, the probe laser field is rapidly attenuated when the control laser field is turned off. This feature allows the creation of a mechanism to turn “off” and “on” the probe laser field through “turning off” and “on” the control laser field, i.e., an all-optical switching mechanism based on EIT. Besides intensity and frequency, the laser field is also characterized by polarization and phase. The EIT has the nature of quantum interference, so it is very sensitive to changes in polarization, especially in the presence of relative phase between laser fields. Therefore, they also significantly affect pulse propagation and optical switching performance. The research results could be helpful for experimental observations or applications in photonic devices such as logic gates, quantum optical information processors, and quantum computers.

Beam shifts controlled by orbital angular momentum in a guided-surface plasmon resonance structure with a four-level atomic medium.

We proposed a scheme to realize tunable giant Goos-Hänchen (GH) and Imbert Fedorov (IF) shifts of the Laguerre-Gauss (LG) beam on a guided-wave surface plasmon resonance (GWSPR) structure backed by a coherent atomic medium with the spontaneously generated coherence (SGC) effect. The orbital angular momentum carried by the incident LG beam can be applied to enhance and control IF shifts but is not beneficial to GH shifts. However, in the presence of SGC effect in the atomic medium, both GH and IF shifts can be simultaneously enhanced and well controlled. With the SGC effect, the linear absorption of the atomic medium vanishes, while the nonlinear absorption of that can be significantly enhanced and controlled by the trigger field, which contributes to controlling of the beam shifts. In particular, the direction of GH shifts can be switched by the Rabi frequency of the trigger field, which can be interpreted as the result of a competition between the inherent damping and the radiative damping corresponding to the nontrivial change in the loci of the reflection coefficients. This scheme provides an effective method to flexibly control and enhance the beam shifts, so it has potential applications in integrated optics, optical sensors, etc.

Influence of spontaneously generated coherence on absorption, dispersion, and group index in a five-level cascade atomic system

By solving the density matrix equations in the steady state, we have derived analytical expressions for the absorption, dispersion, and group index of a five-level cascade-type atomic system as functions of laser intensity and frequency, spontaneously generated coherence (SGC), and relative phase of applied fields. The influences of SGC and relative phase on absorption, dispersion, and group index of this system under electromagnetically induced transparency (EIT) are studied. It is shown that the three EIT windows of system become deeper and narrower as the strength of SGC increases. These lead to an increase in the slope and the amplitude of the dispersion curves at three EIT windows. As a result, the amplitude of the group index at these three EIT windows also becomes larger when the strength of SGC increases. In particular, the group index can easily be switched between negative and positive values i.e., the light propagation can easily be converted between superluminal to subluminal modes by adjusting the strength of SGC, relative phase or the coupling laser intensity.

Optical limiting via spontaneously generated coherence

We investigate the reverse saturable absorption (RSA) and optical limiting (OL) in a three-level V-type quantum system considering the effect of the spontaneously generated coherence (SGC). It is shown that in the absence of the SGC effect, the saturable absorption (SA) is dominant in the system. By taking into account the SGC effect, we prove that the SA dramatically switches to the RSA. Moreover, it is demonstrated that the OL threshold and OL efficiency can be controlled by the SGC effect. In addition, we show that the applied field properties such as detuning can modify the SGC-induced optical limiter efficiency. It is also shown an increase in the atomic density and length of the medium makes the optical limiter more efficient. The analytical calculation shows that the Kerr nonlinearity caused by the SGC effect is the main mechanism of the system evolution. Finally, the theoretical Z-scan experiment is presented to confirm the obtained results. Our proposed scheme can be useful to design controllable atomic optical limiters for optical devices with different sensitivities.

Coherent control of spatial and angular Goos-Hänchen shifts with spontaneously generated coherence and incoherent pumping.

We propose an efficient scheme to manipulate the Goos-Hänchen (GH) shift of a reflected beam from a metal-clad waveguide, where a coherent atomic medium with a Λ-type configuration is employed as the substrate. Using experimentally achievable parameters, we identify the conditions under which spontaneously generated coherence (SGC) allows us to enhance the spatial and angular GH shifts of the reflected beam. With the help of SGC, the relative phases of the probe and control fields can alter the absorption gain and refractive index of the atomic medium, thereby manipulating the magnitudes, signs, and positions of the spatial and angular shifts. Furthermore, the spatial and angular GH shifts can be coherently controlled via adjusting the incoherent pumping rate and the intensity of the control field. Our proposal provides an avenue for the manipulation of spatial and angular GH shifts and potential applications in optical switching and optical steering.

Enhanced magneto-optical rotation of probe field in thermal medium via spontaneous generated coherence

A four-level double lambda closed atomic configuration is considered to study the polarization plane rotation of the probe beam through cold as well as thermal Rb^{87} atomic medium by varying the spontaneously generated coherence (SGC). Magnetic field and strong coupling field are applied to the atomic configuration. The light-matter interaction leads to enhanced the magneto-optical rotation. The intensity of the applied fields plays promising role in the generation and enhancement of birefringence. It ultimately enhances the polarization plane rotation of the probe beam in the Doppler medium. In the presence of both SGC and Doppler broadening effects, the optical rotation and transmission of the weak light beam are modified and controlled as well, which have potential applications in magnetometery and laser frequency stabilization.

Dynamical propagation and all-optical switching in a ladder-type three-level system under the influence of spontaneously generated coherence

We investigate the dynamical of pulse propagation and all-optical switching via a spontaneously generated coherence (SGC) in a three-level ladder-type atomic medium driven by a coupling field under the presence of incoherent pumping. Results show that the SGC causes modulations at the leading edge of the pulse envelope shape. These modulations increase with the together growth of SGC and distance. Furthermore, it is shown that the continuous-wave input probe field is switched ON or OFF by periodically modulating the coupling field. The spontaneously generated coherence has a strong effect on switching efficiency and switching pulse shape. The proposed scheme may have applications in the design of optical switching and optical gain devices in optical telecommunications.

All-optical switching via spontaneously generated coherence, relative phase and incoherent pumping in a V-type three-level system

All-optical switching in a V-type three-level atomic medium is studied and controlled by spontaneously generated coherence (SGC), relative phase of applied fields and incoherent pumping rate. By simultaneously numerical solving the coupled Maxwell–Bloch equations for atom and field on a spatio-temporal grid, we have observed a continuous-wave probe field is switched ON or OFF by periodically modulating the coupling field intensity or the relative phase of applied fields. It also is shows that although the SGC can distort the switching probe pulse, however, under the SGC the response of the medium depends sensitively on the relative phase, and the probe field can be switched synchronous or anti-synchronous with the relative phase. On the other hand, in order to overcome the switching pulse distortion caused by SGC, we have included an incoherent pumping field. By choosing the appropriate phase and pumping rate, the fluctuations of switching probe pulse can be easily overcome. The proposed model can be useful for the design of optical switches and optical storage devices as well as possible experimental implementations.

Coherent Surface Plasmon Hole Burning via Spontaneously Generated Coherence.

Surface plasmon (SP)—induced spectral hole burning (SHB) at the silver-dielectric interface is investigated theoretically. We notice a typical lamb dip at a selective frequency, which abruptly reduces the absorption spectrum of the surface plasmons polaritons (SPP). Introducing the spontaneous generated coherence (SGC) in the atomic medium, the slope of dispersion becomes normal. Additionally, slow SPP propagation is also noticed at the interface. The spectral hole burning dip is enhanced with the SGC effect and can be modified and controlled with the frequency and intensity of the driving fields. The SPP propagation length at the hole-burning region is greatly enhanced under the effect of SGC. A propagation length of the order of 600 µm is achieved for the modes, which is a remarkable result. The enhancement of plasmon hole burning under SGC will find significant applications in sensing technology, optical communication, optical tweezers and nano-photonics.

Electromagnetically induced grating via Kerr nonlinearity and spontaneously generated coherence in a Doppler broadened four-level N-type atomic system

We study the electromagnetically induced grating in a four-level N-type atomic system in the presence of Kerr field, spontaneously generated coherence (SGC), and Doppler broadening. The transmission and diffraction intensity of the probe light is controlled through the Kerr field and the SGC. The gradual increase of the Kerr field and the SGC in the presence of a Doppler broadened medium leads to the enhanced multiple transmission and intensity peaks of the probe light. The electromagnetically induced grating may find applications in a quantized probe field, all-optical switching, routing, and light storage devices.

Effect of spontaneously generated coherence (SGC) on the line shapes of absorption, transparency, dispersion and group index of a four-level inverted Y-type atom–lasers coupling system

Effect of spontaneously generated coherence (SGC) on the line shapes of absorption, transparency, dispersion and group index of a four-level inverted Y-type atom–lasers coupling system

Giant cross-Kerr nonlinearity in a four-level Y-type atomic system

The analytical expression for the group index in a degenerated three-level lambda-type atomic system is derived as a function of the parameters of laser fields and external magnetic field. The influence of the external magnetic field on the group index is investigated. It is shown that by changing the magnitude or sign of the external magnetic field, the transparency window with normal dispersion switches to enhanced absorption with anomalous dispersion at the line center and hence the light propagation can be converted between subluminal and superluminal modes. Full Text: PDF ReferencesR. W. Boyd, "Slow and fast light: fundamentals and applications", J. Mod. Opt. 56 (2009) 1908-1915 CrossRef K.J. Boller, A. Imamoglu, S.E. Harris, "Observation of electromagnetically induced transparency", Phys. Rev. Lett. 66 (1991) 2593. CrossRef A. Lezama, S. Barreiro, and A. M. Akulshin, "Electromagnetically induced absorption", Phys. Rev. A 59 (1999) 4732-4735. CrossRef L. V. Hau, S. E. Harris, Z. Dutton, C. H. Bejroozi, "Light speed reduction to 17 metres per second in an ultracold atomic gas", Nature 397, 594 (1999) CrossRef L. J. Wang, A. Kuzmich, and A. Dogariu, "Gain-assisted superluminal light propagation", Nature 406 (6793), 277-279 (2000) CrossRef A. V. Turukhin, V. S. Sudarshanam, M. S. Shahriar, J. A. Musser, B. S. Ham, P. R. Hammer, "Observation of Ultraslow and Stored Light Pulses in a Solid", Phys. Rev. Lett. 88, 023602 (2002). CrossRef K. Bencheikh, E. Baldit, S. Briaudeau, P. Monnier, J. A. Levenson, and G. Mélin, "Slow light propagation in a ring erbium-doped fiber", Opt. Express 18 (25), 25642-25648 (2010). CrossRef E. E. Mikhailov, V. A. Sautenkov, I. Novikova, G. R. Welch, "Large negative and positive delay of optical pulses in coherently prepared dense Rb vapor with buffer gas", Phys. Rev. A 69, 063808 (2004). CrossRef E. E. Mikhailov, V. A. Sautenkov, Y. V. Rostovtsev, G.R. Welch, "Absorption resonance and large negative delay in rubidium vapor with a buffer gas", J. Opt. Soc. Am. B 21, 425 (2004). CrossRef A. M Akulshin and R. J McLean, "Fast light in atomic media", J. Opt. 12 (2010) 104001. CrossRef Vineet Bharti, Vasant Natarajan, "Sub- and super-luminal light propagation using a Rydberg state", Opt. Comm. 392 (2017) 180-184. CrossRef N.T. Anh, L.V. Doai, D.H. Son, and N.H. Bang, "Manipulating multi-frequency light in a five-level cascade EIT medium under Doppler broadening", Optik 171 (2018) 721-727. CrossRef N.T. Anh, L.V. Doai, and N.H. Bang, "Manipulating multi-frequency light in a five-level cascade-type atomic medium associated with giant self-Kerr nonlinearity", J. Opt. Soc. Am. B 35 (2018) 1233. CrossRef N.H. Bang, L.N.M. Anh, N.T. Dung and L.V. Doai, "Comparative Study of Light Manipulation in Three-Level Systems Via Spontaneously Generated Coherence and Relative Phase of Laser Fields*", Commun. Theor. Phys. 71 (2019) 947-954. CrossRef L.V. Doai, "The effect of giant Kerr nonlinearity on group velocity in a six-level inverted-Y atomic system", Physica Scripta 95 (2020) 035104 (7pp). CrossRef P. Kaur and A. Wasan, "Effect of magnetic field on the optical properties of an inhomogeneously broadened multilevel Λ-system in Rb vapor", Eur. Phys. J. D 71 (2017) 78. CrossRef H. Cheng, H. -M. Wang, S. -S. Zhang, P. -P. Xin, J. Luo and H. -P. Liu, "Electromagnetically induced transparency of 87Rb in a buffer gas cell with magnetic field", J. Phys. B: At. Mol. Opt. Phys. 50 (2017) 095401. CrossRef C. Mishra, A. Chakraborty, A. Srivastava, S. K. Tiwari, S. P. Ram, V. B. Tiwari and S. R. Mishr, "lectromagnetically induced transparency in Λ-systems of 87Rb atom in magnetic field", J. Mod. Opt. 65 (2018) 2269-2277. CrossRef S. H. Asadpour, H. R. Hamedi and H. R. Soleimani, "Slow light propagation and bistable switching in a graphene under an external magnetic field", Laser Phys. Lett. 12 (2015) 045202. CrossRef R. Karimi, S. H. Asadpour, S. Batebi and h. R. Soleimani, "Manipulation of pulse propagation in a four-level quantum system via an elliptically polarized light in the presence of external magnetic field", Mod. Phys. Lett. B 29 (2015) 1550185. CrossRef

Coherent control of surface plasmon polariton via spontaneously generated coherence

We investigate the control over surface plasmon polaritons (SPPs) using the interface between a four-level tripod-type atomic system and a nanocomposite medium under the effect of spontaneously generated coherence (SGC). The absorption and dispersion spectra of SPPs show interesting behavior with SGC effect at the interface. Skin depth of SPPs can be controlled via strength of SGC. The ratio of nanoparticles in the medium also affects different features of SPPs. The horizontal distances traversed by SPPs were also modified with SGC. We show the quantum confinement of SPPs at the interface for different wavelengths. These results can find important practical applications in the fields of atomic spectroscopy, plasmon-based optical devices and sensors technology.

Quantum Entropy in Ladder-Plus-Y Double Quantum Dot System using Spontaneously Generated Coherence

Quantum entropy under spontaneously generated coherence (SGC) was modeled and studied in a double quantum dot (DQD) structure. This system becomes after including the wetting layer (WL) as a ladder-plus-Y- system. The results show that the high probe field under high SGC can give good entanglement between states of the DQD system. Under the high SGC component, the optical pump was more efficient than the probe signal in increasing entanglement. The application of optical fields into WL reduces quantum entropy.

Polarization state and image rotation via spontaneously generated coherence in a spinning fast light medium

In this article we propose a four-level rubidium (Rb87) atomic system for observing interesting features of polarization state rotation in a fast light medium. We investigate spontaneously generated coherence (SGC) for a spinning medium. We show how SGC can affect different spectral profiles of the polarization state and images in this suggested model. We observe a 0.5 radian rotation and 2.5 microsecond time advancement in our proposed system. Our precise results will provide a new platform for researchers in quantum optics due to its applications in image coding, telecommunications and cloaking technology.

Control over spectral hole burning via spontaneously generated coherence and Kerr non-linearity

We study the control over spectral hole burning in four-level N-type system via spontaneously generated coherence (SGC) and Kerr nonlinearity in an inhomogeneous Doppler broadening medium. We consider a co-propagating probe laser beam and a counter-propagating control laser beam at the same time. Multiple spectral holes are created with the spontaneously generated coherence in the medium. The depth of the spectral holes gets deeper with increasing of the Kerr field. We study the group index and the transmission of probe laser pulse in SHB regions that lead us to achieve maximum transmission and much steeper group index in the system with increasing the strength of the Kerr field.

Electromagnetically induced grating in double quantum dot system using spontaneously generated coherence

A model of electromagnetically induced grating (EIG) assisted by the spontaneously generated coherence (SGC) in the ladder-plus-Y double quantum dot (DQD) system is proposed. Using the density matrix theory, the amplitude and phase of the transmission function are studied. It is shown that the transmission is enhanced by the presence of SGC, and the resultant diffraction intensity can increase by controlling the phase. The SGC-assisted EIG controlled by two, three, and four coupling optical fields are studied respectively. Remarkably, we find that the system acquires a huge diffraction intensity when the wetting layer-quantum dot (WL-QD) field is high in the case of four coupling fields.