Electromagnetically Induced Transparency Resonance Research Articles

Interference between electromagnetically induced transparency and N-type resonances in Na vapor

We show theoretically and experimentally that the line shapes observed in ordinary electromagnetically induced transparency (EIT) experiments in sodium atomic vapor can be explained by the superposition of two processes, EIT and N-type resonances (NTR). When the higher frequency side of the Doppler absorption profile is excited, EIT is dominant, whereas, for the lower frequency side, NTR is dominant, and, in between, interference between EIT and NTR takes place. Theoretical simulations, based on a perturbative approach, agreed reasonably well with the experimental observations. The signal behavior concerning ac Stark shifts has also been studied for EIT and NTR; it was found that, although the signal peak always shifts toward the higher frequency in the case of EIT, for NTR, the shift can be nullified by adjusting the power balance of the two incident beams.

EIT line shape in an open and partially closed multilevel V-type system

A detail theoretical analysis based on density matrix formulation is carried out to study the electromagnetically induced transparency in a multilevel open V-type system. The density matrix equations are solved numerically for both the Doppler-free and Doppler-broadened medium. We get two coherent electromagnetically induced transparency (EIT) peaks of sub-natural line width and five saturation peaks of sub-Doppler line width. The effect of decoherence on the EIT peak is studied using the theoretical model. A comparative study of the EIT line shape for open and closed V-type system has been done using the theoretical results. In our experiment, we have observed one EIT peak and four saturation peaks in an open V-type system corresponding to the D2 transition of 85Rb atoms and the EIT peak gets enhanced for partially closed V-type system compared to the open system. The dependence of height and width of the EIT line shape for different pump power values is also observed. The experimental observations are simulated numerically with a good agreement. We have also reported a noticeable change in the contrast of the EIT resonance due to the tuning of the pump laser frequency over the entire probe Doppler profile.

Relationship between electromagnetically-induced transparency and Autler–Townes splitting in a Doppler-broadened system**Project supported by the National Natural Science Foundation of China (Grant Nos. 11404330, 11274376, 61308011, and 11474347), the NSAF, China (Grant No. U1330117), the National Basic Research Program of China (Grant Nos. 2013CB922002 and 2010CB922904), and the China Postdoctoral Science Foundation (Grant No. 119103S239).

We study the relationship between electromagnetically-induced transparency (EIT) and Autler–Townes (AT) splitting in a cascade three-level Doppler-broadened system. By comparing the absorption spectrum with the fluorescence excitation spectrum, it is found that for a Doppler-broadened system, EIT resonance cannot be explained as the result of quantum interference, unlike the case of a homogeneously broadened system. Instead, the macroscopic polarization interference plays an important role in determining the spectra of EIT and AT splitting, which can be explained within the same framework when being detected by the absorption spectra.

Tunable Fano Resonances and Electromagnetically Induced Transparency in All-Dielectric Holey Block

The optical properties of a simple planar silicon nanoblock with cylindrical hole operating at terahertz (THz) frequencies are investigated. The proposed nanostructure exhibit low loss electromagnetically induced transparency (EIT) and Fano resonances, which arises due to the near-field coupling between the nanoblock and cavity modes. The line shape of these resonances can be considerably modified and tuned by varying the geometrical parameters. Furthermore, the symmetry breaking conception is also introduced, which enables higher-order dark hybridized modes to interact with each other, resulting in a dual EIT and Fano resonances in the optical spectrum. The EIT and Fano resonances present high local field enhancement (33) and Q-factors (584) due to extremely low absorption loss. This makes the proposed design an ideal platform for low loss slow-light devices and multi-wavelength biosensing applications.

Transition from Autler–Townes splitting to electromagnetically induced transparency based on the dynamics of decaying dressed states

The threshold for the transition between Autler–Townes splitting (ATS) and electromagnetically induced transparency (EIT) is studied through examining the dynamics of decaying dressed states, which are derived from the effective Hamiltonian. It is found that the threshold corresponds to the suppression of the Rabi oscillation of the populations by the relaxation as the coupling field becomes weak. Moreover, ATS and EIT belong to two different regimes, the former being in the non-perturbation regime, where there is coherent Rabi oscillation of the populations of the states coupled by the coupling field. By contrast, EIT is in the perturbation regime, and the transparency window in the EIT resonance can be explained as being due to the gain of the four-wave mixing process. Experiments are performed in cold rubidium atoms, where both the absorption and dispersion are measured, showing that EIT can be discriminated from ATS through Fourier transformation of the spectra. Compared to the statistical method proposed by Anisimov et al (2011 Phys. Rev. Lett. 107 163604), our method is more direct and is deterministic.

High-contrast dark resonances on the D1 line in cesium nanocell: the advantages compared with the other alkali D lines

Electromagnetically induced transparency (EIT) effect in a -system formed by Cs atoms line, enclosed in nanometric-thin cells, is studied both experimentally and theoretically for the first time. The atomic column thickness varies in the range of 50–1500 nm. It is demonstrated that when the coupling laser frequency is in exact resonance with the corresponding atomic transition, the parameters of the EIT resonance (also called dark resonance (DR)) depend weakly on , which allows us to detect DR at nm with the contrast of . The obtained DR parameters are the best as compared with those for Rb and lines and Cs line. The DR contrast and width are studied versus laser frequency detunings, coupling laser power, cell thickness, temperature, and applied external magnetic field. The well-resolved splitting of the DR resonance in a magnetic field for nm can be used for magnetometry with high spatial resolution. The theoretical model describes well the observed results.

Transient development of Zeeman electromagnetically induced transparency during propagation of Raman–Ramsey pulses through Rb buffer gas cell

We investigate, experimentally and theoretically, time development of Zeeman electromagnetically induced transparency (EIT) during propagation of two time separated polarization laser pulses, preparatory and probe, through Rb vapour. The pulses were produced by modifying laser intensity and degree of elliptical polarization. The frequency of the single laser beam is locked to the hyperfine transition of the D1 line in 87Rb. Transients in the intensity of component of the transmitted light are measured or calculated at different values of the external magnetic field, during both preparatory and probe pulse. Zeeman EIT resonances at particular time instants of the pulse propagation are reconstructed by appropriate sampling of the transients. We observe how laser intensity, Ramsey sequence and the Rb cell temperature affect the time dependence of EIT line shapes, amplitudes and linewidths. We show that at early times of the probe pulse propagation, several Ramsey fringes are present in EIT resonances, while at later moments a single narrow peak prevails. Time development of EIT amplitudes are determined by the transmitted intensity of the component during the pulse propagation.

Macroscopic effects in electromagnetically-induced transparency in a Doppler-broadened system**Project supported by the National Natural Science Foundation of China (Grant Nos. 10974252, 11274376, 60978002, and 11179041), the National Basic Research Program of China (Grant No. 2010CB922904), the National High Technology Research and Development Program of China (Grant No. 2011AA120102), the Natural Science Foundation of Inner Mongolia, China (Grants No. 2012MS0101), and

We study the electromagnetically-induced transparency (EIT) in a Doppler-broadened cascaded three-level system. We decompose the susceptibility responsible for the EIT resonance into a linear and a nonlinear part, and the EIT resonance reflects mainly the characteristics of the nonlinear susceptibility. It is found that the macroscopic polarization interference effect plays a crucial role in determining the EIT resonance spectrum. To obtain a Doppler-free spectrum there must be polarization interference between atoms of different velocities. A dressed-state model, which analyzes the velocities at which the atoms are in resonance with the dressed states through Doppler frequency shifting, is employed to explain the results.

Optical Ramsey fringes observed during temporal evolution of Zeeman coherences in Rb buffer gas cell

We experimentally studied the temporal evolution of Zeeman electromagnetically induced transparency (EIT) resonances induced by the laser resonant to hyperfine transition of 87Rb in a rubidium buffer gas cell. We simultaneously modulated the laser beam intensity and polarization to achieve the repeated interaction of the laser beam with coherently prepared atoms. Our cell was placed in a homogenous magnetic field to obtain the Larmor precession of the phase of coherences. The weak laser beam was used to probe the atoms at the end of the Ramsey sequence. We measured the transparency of the probe pulse at different magnetic fields for a given excitation pulse and the period of free evolution of Zeeman coherences in the dark. From these data, we reconstructed the temporal evolution of EIT resonances. The Ramsey fringes that appeared on the EIT curves at the beginning of the second probing pulse disappeared at later moments due to various decay processes.

All-optical electromagnetically induced transparency using one-dimensional coupled microcavities.

We report the first experimental realization of all-optical electromagnetically induced transparency (EIT) via a pair of coherently interacting SiO2 microcavities in a one-dimensional SiO2/Si3N4 photonic crystal consisting of a distributed Bragg reflector (DBR). The electromagnetic interactions between the coupled microcavities (CMCs), which possess distinct Q-factors, are controlled by varying the number of embedded SiO2/Si3N4 bilayers in the coupling DBR. In case of weak microcavity interactions, the reflectivity spectrum reveals an all-optical EIT resonance which splits into an Autler-Townes-like resonance under condition of strong microcavity coupling. Our results open up the way for implementing optical analogs of quantum coherence in much simpler one-dimensional structures. We also discuss potential applications of CMCs.

High-contrast atomic dark resonances formed in a ladder system of rubidium atoms in submicron structures

It is shown that high-contrast resonance of electromagnetically induced transparency (EIT) in a ladder Ξ-system of 5S 1/2-5P 3/2-5D 5/2 levels can be formed in optical cells containing a column of rubidium vapor with thickness L in an interval of 100 nm ≤ L ≤ 780 nm. Using bichromatic laser radiation with certain parameters, an 83% contrast of the EIT resonance (or dark resonance, DR) has been achieved for a vapor column thickness of L = 780 nm. An important condition for the formation of high-contrast DR is that the frequency of the coupling laser radiation must be resonant with the frequency of the corresponding 5P 3/2-5D 5/2 transition (for the probe radiation frequency scanned over the 5S 1/2-5P 3/2 transition). It is also shown that a DR can be formed at a record small vapor column thickness of L ≈ 100 nm. Expressions that can be used to estimate the expected DR width at small L values are presented.

Resolving multiple peaks using a sub-transit-linewidth cross-correlation resonance

In a recent paper [L. Feng et al., Phys. Rev. Lett. 109, 233006 (2012)], we demonstrated a sub-transit-linewidth resonance based on cross correlation between optical fields in an electromagnetically induced transparency (EIT) system. Here, we investigate the ability of such resonance to resolve multiple resonance peaks. We first report the implementation of the cross-correlation resonance in a hyperfine EIT system, with a linewidth of about $1/16$ of the transit EIT width. Then, a magnetic field is applied to create multipeak EIT resonance with tunable spacing. Cross-correlation resonance with multipeaks is observed and the line shape agrees qualitatively with our numerical simulations. We find that the multipeak correlation resonance has better contrast than the corresponding EIT resonance, but with a lower signal to noise. Furthermore, this correlation resonance cannot resolve peaks with spacing close to or less than the intrinsic width, like any other resonance techniques. We analyze the origin of this limitation and make connections to the Ramsey-type subnatural spectroscopy technique. This work shows potential applications of the correlation resonance in atomic frequency standard and laser spectroscopy.

Effects of laser beam diameter on electromagnetically induced transparency due to Zeeman coherences in Rb vapor

We experimentally studied the effects of laser beam diameter on electromagnetically induced transparency (EIT) due to Zeeman coherences induced by a laser resonant with the hyperfine transition Fg = 2 → Fe = 1 of 87Rb in a rubidium buffer gas cell. We use two laser beams of Gaussian intensity radial profile for laser beam diameters of 6.5 and 1.3 mm, laser intensities in the range of 0.1–35 mW cm−2 and cell temperatures between 60 and 82 °C. The results show that the amplitude of the normalized EIT resonance has a maximum at a laser intensity which depends on laser beam diameter and cell temperature. The laser intensity corresponding to the maximum EIT amplitude is higher for a smaller laser beam and higher cell temperature. The linewidth of Zeeman EIT resonance varies nearly linearly with laser intensity, almost independent of cell temperature and laser beam diameter.

Third-harmonic generation in resonant-metamaterial-based photonic-band-gap materials

We present large enhancement of the nonlinear wave mixing process (third-harmonic generation) in photonic-band-gap materials made of negative and positive index media, at the band edge of the zero-$\overline{n}$ band gap. Incorporating metamaterial-based, electromagnetically induced transparency (EIT)--like resonance in the nonlinear layer leads to unprecedented line narrowing of the generated third harmonic. This scheme permits the mapping of the narrow EIT resonance at the fundamental frequency to the generated third-harmonic frequency with even narrower line shape.

Power-broadening-free correlation spectroscopy in cold atoms

We report a detailed investigation on the properties of correlation spectra for cold atoms under the condition of Electromagnetically Induced Transparency (EIT). We describe the transition in the system from correlation to anti-correlation as the intensity of the fields increases. Such transition occurs for laser frequencies around the EIT resonance, which is characterized by a correlation peak. The transition point between correlation and anti-correlation is independent of power broadening and provides directly the ground-state coherence time. We introduce a method to extract in real time the correlation spectra of the system. The experiments were done in two distinct magneto-optical traps (MOT), one for cesium and the other for rubidium atoms, employing different detection schemes. A simplified theory is introduced assuming three-level atoms in $\Lambda$ configuration interacting with a laser with stochastic phase fluctuations, providing a good agreement with the experimental observations.

Electromagnetically Induced Transparency in a Diamond Spin Ensemble Enables All-Optical Electromagnetic Field Sensing

We use electromagnetically induced transparency (EIT) to probe the narrow electron-spin resonance of nitrogen-vacancy centers in diamond. Working with a multipass diamond chip at temperatures 6-30 K, the zero-phonon absorption line (637 nm) exhibits an optical depth of 6 and inhomogeneous linewidth of ~30 GHz FWHM. Simultaneous optical excitation at two frequencies separated by the ground-state zero-field splitting (2.88 GHz) reveals EIT resonances with a contrast exceeding 6% and FWHM down to 0.4 MHz. The resonances provide an all-optical probe of external electric and magnetic fields with a projected photon-shot-noise-limited sensitivity of 0.2 V/cm/√[Hz] and 0.1 nT/√[Hz], respectively. Operation of a prototype diamond-EIT magnetometer measures a noise floor of ~/<1 nT/√[Hz] for frequencies above 10 Hz and Allan deviation of 1.3±1.1 nT for 100 s intervals. The results demonstrate the potential of diamond-EIT devices for applications ranging from quantum-optical memory to precision measurement and tests of fundamental physics.

Temperature and magnetic field effects on the coherent and saturating resonances in Λ- and V-type systems for the 85Rb-D2 transition

Variations of the coherent resonance, i.e. an electromagnetically induced transparency (EIT) peak with the cell temperature in Λ- and V-type systems are observed for the 85Rb-D2 transition. In a Λ-type system, the amplitude of the EIT peak gradually decreases and it is finally masked by the broadened optical pumping dips with the increase of the cell temperature. But for the V-type system, the EIT and the saturation peaks are greatly enhanced with the increase of the cell temperature. The effect of the external magnetic field on the EIT resonance is also investigated considering both types of systems. For the Λ-type system in place of a single EIT resonance, five transparency windows with broadened width and reduced contrast are obtained depending on the Zeeman levels formed by the applied magnetic field. In the V-type system, the coherent resonance peak could not be resolved in the presence of the external magnetic field, but a greater number of saturation peaks with broadened width appear in the probe transmission spectrum. A theoretical model is adopted to represent the experimental results. Good agreement is found between the experimental and numerically simulated results.

Physical interpretation for the correlation spectra of electromagnetically-induced-transparency resonances

The phenomenon called Electromagnetically Induced Transparency (EIT) may induce different types of correlation between two optical fields interacting with an ensemble of atoms. It is presently well known, for example, that in the vicinity of an EIT resonance the dominant correlations at low powers turn into anti-correlations as power increases. Such correlation spectra present striking power-broadening-independent features, with the best condition for measuring the characteristic linewidth occurring at the highest powers. In the present work we investigate the physical mechanisms responsible for this set of observations. Our approach is first to reproduce these effects in a better controlled experimental setup: a cold atomic ensemble, obtained from a magneto-optical trap. The results from this conceptually simpler system were then compared to a correspondingly simpler theory, which clearly relates the observed features to the interplay between two key aspects of EIT: the transparency itself and the steep normal dispersion near two-photon resonance.

High resolution spectroscopy of Cs vapor confined in optical cells of few-micron thicknesses

We present here the new behavior of Electromagnetically Induced Transparency (EIT), Velocity Selective Optical Pumping (VSOP) and Velocity Selective Excitation (VSE) resonances observed in Cs vapor confined in unique cells with thicknesses L = 1.5λ and L = 6λ. It is shown experimentally that in both cells, the EIT resonance is significantly narrower than would be expected from the ground state dephasing rate due to atomic collisions with the cell windows. The enhanced absorption (fluorescence) narrow VSOP resonance at the closed transition transforms into reduced absorption (fluorescence) one with small increase of atomic concentration or light intensity. A striking difference appears between the VSE resonance broadening due to excited atom thermalization, in L = 6λ and conventional L = 2.5 cm cells.

Splitting of the electromagnetically induced transparency resonance on 85Rb atoms in strong magnetic fields up to the Paschen-Back regime

Electromagnetically induced transparency (EIT) resonance in strong magnetic fields of up to 1.7 kG has been investigated with the use of a 30-μm cell filled with an atomic rubidium vapor and neon as a buffer gas. The EIT resonance in the Λ system of the D1 line of 85Rb atoms has been formed with the use of two narrowband (∼1 MHz) 795-nm diode lasers. The EIT resonance in a longitudinal magnetic field is split into five components. It has been demonstrated that the frequencies of the five EIT components are either blue- or red-shifted with an increase in the magnetic field, depending on the frequency νP of the probe laser. In has been shown that in both cases the 85Rb atoms enter the hyperfine Paschen-Back regime in magnetic fields of >1 kG. The hyperfine Paschen-Back regime is manifested by the frequency slopes of all five EIT components asymptotically approaching the same fixed value. The experiment agrees well with the theory.