Ac Stark Effect Research Articles

Continuous broadband Rydberg receiver using AC Stark shifts and Floquet states

We demonstrate the continuous broadband microwave receivers based on AC Stark shifts and Floquet states of Rydberg levels in a cesium atomic vapor cell. The resonant transition frequency of two adjacent Rydberg states 78 S1/2 and 78 P1/2 is tuned based on AC Stark effect of 70 MHz radio frequency (RF) field that is applied outside the vapor cell. The use of the j=1/2 Rydberg states ensures that only a single mj sublevel is involved. The generated Rydberg Floquet states act to enhance the sensitivity of the AC-Stark-tuned states when the frequency is matched and further extend the bandwidths. We achieve microwave field measurements with over 1.172 GHz continuous frequency tuning and a sensitivity ranging from 280.2 nVcm−1Hz−1/2 to 14.6 μ Vcm−1Hz−1/2. The achieving of continuous frequency and high sensitivity microwave detection will promote the application of Rydberg receivers in the radar technique and wireless communication.

Control resonant excitation of surface plasmon polariton in quantum-dot molecule system via tunneling induced transparency and Autler–Townes splitting

Electromagnetic induced transparency (EIT) and Autler–Townes splitting (ATS) both produce a transparency window in an absorption profile, yet EIT is distinct in that it can create a transparency window for a weak control field. To elucidate the distinct physical mechanisms underlying EIT and ATS effects, we explore the controlled resonant excitation of surface plasmon polaritons (SPPs) within these regimes. Our setup is composed of three layers: a top vacuum or air layer, a central metal film, and a bottom layer of dielectric medium based on the quantum-dot molecules (QDMs) system. Unlike typical systems, that employ prism or grating coupling scheme, our setup takes advantage of the unique features of the QDMs medium to investigate the direct resonance excitation of SPPs. A weak probe and a strong control field are carried through air or vacuum to the top layer. Our results demonstrate that the permittivity of the bottom medium displays tunneling induced transparency (TIT) if the tunneling strength (Te) and the decay rate of the direct exciton (Γ1) follow the condition Te/Γ1⩽0.5; otherwise, it represents the ATS effect. In both instances, the permittivity of the QDMs medium satisfy the low-loss (high transmission) criteria, i.e., Re [ɛd]<1 and Im [ɛd]≪1, providing a framework for exploring the control resonant excitation of SPPs. We simulate the reflection and transmission spectra using the Fresnel’s formula and noticed sharp dips in reflection and peaks in the transmission spectra, which are the signature of coupler free resonance excitation of SPPs. We noticed that the narrow peak in TIT allows for strong light transmission and thus a high peak in SPP resonance excitation, resulting in higher sensitivity in plasmonic sensors. Conversely, the large spacing between the two peaks in the ATS effect broadens the range of effective excitation frequencies for SPPs, increasing the system’s adaptability and efficiency in applications requiring broad spectrum responses.

Use of the 5P3/2→6P3/2 electric dipole forbidden transition in Rb as a non-perturbing probe of atom dynamics in an operating magneto-optical trap

Abstract Results of spectroscopy experiments using the $5P_{3/2} \to 6P_{3/2}$ electric dipole forbidden transition in cold rubidium atoms are presented. Production of this forbidden transition is detected by observing the emission of the $420 $ nm fluorescence photons that result from the decay of the $6P_{3/2} $ state into the ground state. The experiments are performed under the steady state operation conditions of a magneto-optical trap (MOT), and thus provide non-perturbing information on the atom-light system. The hyperfine structure of the $6P_{3/2}$ level is completely resolved, and the fluorescence peaks show the expected Autler-Townes (AT) splitting of the emission lines. This hyperfine structure is used to calibrate the frequency scale of all spectra recorded. A combination of this absolute frequency scale and an expression for the AT profile allows an absolute determination of the effective Rabi frequency and detuning of the MOT. The behavior of these AT doublets is studied as a function of frequency detuning and also as a function of the trapping light intensity.&amp;#xD;The experiments also take full advantage of the strong polarization dependence of the relative intensities of the hyperfine fluorescence components.&amp;#xD;This study results in a sensitive probe of the relative populations of the magnetic sublevel projections relative to the trapping magnetic field gradient.&amp;#xD;An almost isotropic population distribution was found, but small deviations from isotropy could be determined with this electric dipole forbidden probe.

Simultaneously measuring microwave electric fields at different frequencies by Rydberg-atom-based electrometry with Zeeman-resolved Autler–Townes splitting

We provide the simultaneous traceable measurements of microwave electric fields at two different frequencies by the electromagnetically induced transparency (EIT) and Autler–Townes (AT) splitting. A static magnetic field working together with a linearly polarized probe and coupling light prepares Rydberg atoms in Zeeman sublevels with maximal |mJ| in an atomic vapor cell. Using the EIT-AT splitting of these two maximal |mJ| states, the microwave electric fields at two different frequencies are simultaneously measured, in which their frequency difference can be adjustable within the linear range of magnetic field-induced level shifts. The proposed method provides a promising prospect for calibrating multiple microwave frequencies simultaneously in the future.

Microwave field sensor based on cold cesium Rydberg three-photon electromagnetically induced spectroscopy

Abstract We present the electromagnetically induced transparency (EIT) spectra of cold Rydberg four-level cascade atoms consisting of the 6S1/2 → 6P3/2 → 7S1/2 → 60P3/2 scheme. A coupling laser drives the Rydberg transition, a dressing laser couples two intermediate levels and a weak probe laser probes the EIT signal. We numerically solve the Bloch equations and investigate the dependence of the probe transmission rate signal on the coupling and dressing lasers. We find that the probe transmission rate can display an EIT or electromagnetically induced absorption (EIA) profile, depending on the Rabi frequencies of the coupling and dressing lasers. When we increase the Rabi frequency of the coupling laser and keep the Rabi frequency of the probe and dressing laser fixed, flipping of the EIA to EIT spectrum occurs at the critical coupling Rabi frequency. When we apply a microwave field coupling the transition 60P3/2 → 61S1/2, the EIT spectrum shows Autler–Townes splitting, which is employed to measure the microwave field. The theoretical measurement sensitivity can be 1.52 × 10−2 nV⋅cm−1⋅Hz−1/2 at the EIA–EIT flipping point.

High-order Autler–Townes splitting in electrically tunable photonic molecules

Whispering gallery mode optical microresonators represent a promising avenue for realizing optical analogs of coherent light–atom interactions, circumventing experimental complexities. All-optical analogs of Autler–Townes splitting have been widely demonstrated, harnessing coupled optical microresonators, also known as photonic molecules, wherein the strong coupling between resonant fields enables energy level splitting. Here, we report the characterizations of Autler–Townes splitting in waveguide-coupled microring dimers featuring mismatched sizes. By exploiting backscattering-induced coupling via Rayleigh and Mie scatterers in individual rings, high-order Autler–Townes splitting has been realized, yielding supermode hybridization in a multi-level system. Upon resonance detuning using an integrated phase shifter, intra-cavity coupling-induced splitting becomes almost indistinguishable at the zero-detuning point where the strong inter-cavity coupling counteracts the imbalance of backscattering strengths in individual rings. Through demonstrations on the maturing silicon photonics platform, our findings establish a framework of electrically tunable photonic molecules for coupling-mediated Autler–Townes splitting, offering promising prospects for on-chip signal generation and processing across classical and quantum regimes.

Wavelength-tunable high-fidelity entangled photon sources enabled by dual Stark effects

The construction of a large-scale quantum internet requires quantum repeaters containing multiple entangled photon sources with identical wavelengths. Semiconductor quantum dots can generate entangled photon pairs deterministically with high fidelity. However, realizing wavelength-matched quantum-dot entangled photon sources faces two difficulties: the non-uniformity of emission wavelength and exciton fine-structure splitting induced fidelity reduction. Typically, these two factors are not independently tunable, making it challenging to achieve simultaneous improvement. In this work, we demonstrate wavelength-tunable entangled photon sources based on droplet-etched GaAs quantum dots through the combined use of AC and quantum-confined Stark effects. The emission wavelength can be tuned by ~1 meV while preserving an entanglement fidelity f exceeding 0.955(1) in the entire tuning range. Based on this hybrid tuning scheme, we finally demonstrate multiple wavelength-matched entangled photon sources with f > 0.919(3), paving the way towards robust and scalable on-demand entangled photon sources for quantum internet and integrated quantum optical circuits.

Acceleration-induced spectral beats in strongly driven harmonic oscillators

The harmonic modulation of coherent systems gives rise to a wealth of physical phenomena, e.g., the AC-Stark effect and Mollow triplets, with important implications for coherent control and frequency conversion. Here, we demonstrate a novel regime of temporal coherence in oscillators harmonically driven at extreme energy modulation amplitudes relative to the modulation quantum. The studies were carried out by modulating a confined exciton-polariton Bose-Einstein condensate (BEC) by an acoustic wave. Features of the new regime are the appearance, in the spectral domain, of a comb of resonances termed acceleration beats with energy spacing tunable by the modulation amplitude and, in the time domain, of temporal correlations at time scales much shorter than the acoustic period, which also depend on the modulation amplitude. These features are quantitatively accounted for by a theoretical framework, which associates the beats with accelerated energy-change rates during the harmonic cycle. These observations are underpinned by the high sensitivity of the BEC energy to the acoustic driving, which simultaneously preserves the BEC’s temporal coherence. The acceleration beats are a general feature associated with accelerated energy changes: analogous features are thus also expected to appear under highly accelerated motion e.g., in connection with Cherenkov and Hawking radiation.

Atomic-like Autler–Townes splitting controlled by destructive and constructive natural non-Hermitian quantization in Eu3+: BiPO4

We report atomic-like Autler–Townes splitting controlled by destructive and constructive natural non-Hermitian quantization in Eu3+: BiPO4. For the first time, we explored destructive and constructive AT splitting in different regions. Fluorescence (FL), spontaneous four-wave mixing (SFWM), and shot noise signals exhibit different kinds of AT splitting. FL signal exhibits three level dip AT splitting through destructive quantization, SFWM signals exhibit peak and multi-dip AT splitting through constructive quantization, and shot noise signals exhibit a two-level dip AT splitting. These kinds of AT splitting originate through single photon dressing and double photon–phonon dressing, which can be controlled by adjusting experimental parameters. Our atomic-like Autler–Townes-splitting technique is useful for making a spectral router.

Hyperfine interaction in the Autler-Townes effect: Control of two-photon selection rules in the Morris-Shore basis

Hyperfine interaction in the Autler-Townes effect: Control of two-photon selection rules in the Morris-Shore basis

Real-imaginary spectrum decomposition of the transparency spectra in microwave dressed Rydberg systems

To distinguish the contributions of electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) in their applications in precision laser spectroscopy, we propose a real-imaginary spectrum decomposition method to investigate the transparency spectra in a four-level microwave (MW) dressed Rydberg system. We show that the opening transparency windows in the absorption spectra of probe field is a prominent character by EIT, EIT-ATS crossover, and ATS when the MW field is turned off and the intensity of the control field is adjusted. When the MW field is turned on and gradually increased, the EIT is destroyed and disappears. In addition, the most prominent characters that open a transparency window are the EIT-ATS crossover and the ATS. Then, if we further increase the intensity of the MW field, we find that the transparency windows open mainly due to the ATS. Compared to the previous considerations of this issue, which were limited to three-level systems, our four-level scheme reported here is useful for understanding the features of quantum interference in multilevel atomic systems, and has potential applications to study enhanced sensitivity, measurement spectroscopic, quantum processing, quantum communication, and transmission.

Quantum entropic exchange at avoided crossings due to laser–atom interaction

In the present study, we detail the entropic characteristics of a dressed atom, wherein the atom undergoes an interaction with a monochromatic laser beam. Our investigation of the laser–atom interplay employs a well-established non-perturbative quasi-energy methodology, allowing us to discern the dressed wavefunctions and quasi-energies of the laser-dressed atom. Utilizing these dressed wavefunctions as a foundation, we systematically examine various entropic measures, observing their behaviour for laser frequency and intensity. The selection of levels within the system adheres to the criteria dictated by the selection rules governing transitions between these levels. Our exploration focuses on the interplay between Shannon entropy and other entropic metrics, with their fluctuations intricately tied to the phenomenon of avoided crossings. As the laser amplitude intensifies, the AC Stark effect takes centre stage, exerting influence over the sharp or smooth variations in Shannon entropy at these avoided crossings. Furthermore, we delineate the correlation between the number of levels considered and the identification of avoided crossings. Our present analysis sheds light on the intricate dynamics in the dressed atom system, enhancing our understanding of the interplay between laser-induced dressing and entropic measures.

Dynamically enhanced Autler–Townes splitting by orthogonal XUV fields

Abstract Based on numerical solutions of the time-dependent Schrödinger equation, we theoretically investigate the photoelectron spectrum of hydrogen atoms ionized by a pair of ultrashort, intense, and orthogonally polarized laser pulses with a relative time delay in a pump–probe configuration. The pump pulse resonantly excites electrons from the 1s and 2p levels, inducing Rabi oscillations. The resulting dynamically enhanced Autler–Townes (AT) splitting is observed in the photoelectron energy spectrum upon interaction with the second probe pulse. In contrast to the previous parallel-polarization scheme, the proposed orthogonal-polarization configuration enables the resolution of dynamically enhanced AT splitting over a considerably wider range of probe photon energies.

Controllable nonreciprocal single-photon frequency converter via a four-level system

We propose an efficient, nonreciprocal single-photon device that achieves single-photon routing and frequency conversion through chiral coupling of two one-dimensional waveguides with a four-level atom. Photons incoming from one port can be definitely directed to another port. However, the photon frequency conversion has been achieved only when the single photons are transferred from one waveguide to the other, and its probability can reach unity. Applied the on-demand classical field to drive an atom, the transmission quantum tunneling path can be turned off and on by exploiting the Autler–Townes splitting mechanism. Our results illustrate the potential of our device for applications in a quantum network.

High angular momentum coupling for enhanced Rydberg-atom sensing in the very-high frequency band

Recent advances in Rydberg-atom electrometry detail promising applications in radio frequency communications. Presently, most applications use carrier frequencies greater than 1 GHz where resonant Autler–Townes splitting provides the highest sensitivity. This letter documents a series of experiments with Rydberg atomic sensors to collect and process waveforms from the automated identification system (AIS) used in maritime navigation in the very high frequency (VHF) band. Detection in this band is difficult with conventional resonant Autler–Townes based Rydberg sensing and requires a new approach. We show the results of a method called high angular momentum matching excited Raman (HAMMER), which enhances low frequency detection and exhibits superior sensitivity compared to the traditional AC Stark effect. From measurements of electromagnetically induced transparency in rubidium and cesium vapor cells, we show the relationship between incident electric field strength and observed signal-to-noise ratio and find that the sensitivity of the HAMMER scheme in rubidium achieved an equivalent single VHF tone sensitivity of 100μV/m/Hz. With these results, we estimate the usable range of the atomic vapor cell antenna for AIS waveforms given current technology and detection techniques.

Interaction-Induced ac Stark Shift of Exciton-Polaron Resonances.

Laser-induced shift of atomic states due to the ac Stark effect has played a central role in cold-atom physics and facilitated their emergence as analog quantum simulators. Here, we explore this phenomenon in an atomically thin layer of semiconductor MoSe_{2}, which we embedded in a heterostructure enabling charge tunability. Shining an intense pump laser with a small detuning from the material resonances, we generate a large population of virtual collective excitations and achieve a regime where interactions with this background population are the leading contribution to the ac Stark shift. Using this technique we study how itinerant charges modify-and dramatically enhance-the interactions between optical excitations. In particular, our experiments show that the interaction between attractive polarons could be more than an order of magnitude stronger than those between bare excitons.

Difference‐Frequency Generation with and without Quantum Interference in Superconducting Circuits

AbstractElectromagnetically induced transparency (EIT) plays an important role in enhancing nonlinear optical processes at the quantum level. This paper proposes an accessible scheme for realizing high‐efficiency second‐order nonlinear difference‐frequency generation beyond the conventional EIT technique in superconducting circuits. By designing two subsystems to create two transparency windows from Autler–Townes splitting (ATS), a dual‐ATS mechanism is triggered in the scheme. This mechanism leads to an efficient difference‐frequency generation, and the efficiency obtained here can be four orders of magnitude larger than that of the EIT scheme. This study may pave a way for exploring ATS‐enhanced nonlinear optics.

Coherence as an indicator to discern electromagnetically induced transparency and Autler–Townes splitting

Electromagnetically induced transparency (EIT) and Autler–Townes splitting (ATS) are generally characterized and distinguished by the width of the transparency created in the absorption profile of a weak probe in presence of a strong control field. This often leads to ambiguities, as both phenomena yield similar spectroscopic signatures. However, an objective method based on Akaike’s information criterion (AIC) test offers a quantitative way to discern the two regimes when applied on the probe absorption profile. The obtained transition value of control field strength was found to be higher than the value given by pole analysis of the corresponding off-diagonal density matrix element. By contrast, we apply the test on ground state coherence and the measured coherence quantifier, which yields a distinct transition point around the predicted value even in presence of noise. Our test accurately captures the transition between two regimes, indicating that a proper measure of coherence is essential for making such distinctions.

The 5P3/2→6PJ(J=1/2,3/2) Electric Dipole Forbidden Transitions in Rubidium

This paper presents a general review of the results of the experimental and theoretical work carried out by our research group to study the 5P3/2→6PJ electric quadrupole transition in atomic rubidium. The experiments were carried out with room-temperature atoms in an absorption cell. A steady-state population of atoms in the 5P3/2 excited state is produced by a a narrow-bandwidth preparation laser locked to the D2 transition. A second CW laser is used to produce the forbidden transition with resolution of the 6PJ hyperfine states of both rubidium isotopes. The process is detected by recording the 420(422) nm fluorescence that occurs when the atoms in the 6PJ state decay directly into the 5S ground state. The fluorescence spectra show a strong dependence on the relative polarization directions of the preparation laser and the beam producing the forbidden transition. This dependence is directly related to a strong anisotropy in the populations of the 5P3/2 intermediate magnetic substates, and also to the electric quadrupole selection rules over magnetic quantum numbers. A calculation based on the rate equations that includes velocity and detuning dependent transition rates is adequate to reproduce these results. The forbidden transition is also shown to be an ideal probe to measure the Autler–Townes splitting generated in the preparation of the 5P3/2 state. Examples of spectra obtained with cold atoms in a magneto-optical trap (MOT) are also presented. These spectra show the expected Autler–Townes doublet structure with asymmetric line profiles that result as a consequence of the red-detuning of the trapping laser in the MOT.

Control of a single-photon router via an extra cavity

Controllable single-photon routing plays an important role in quantum networks. We investigate single-photon scattering in two one-dimensional (1D) waveguides by a three-level emitter with a cascade configuration, which is a dipole coupled to an extra cavity. The tunneling path for the transmission of a single photon is switched by whether the extra cavity contains photons. For the setup, the Autler–Townes splitting is modulated by the extra cavity, in which the transmission valley (reflection range) width is tunable in terms of the number of photons in the extra cavity. Our investigation will be beneficial to single-photon routing in quantum networks using quantifiable photon numbers in an extra cavity.