Three-photon Resonance Research Articles

Phase control of asymmetrical Mollow sideband in a Δ-type superconducting artificial atom

Abstract We investigate the resonance fluorescence spectrum (RFS) from a three-level Δ -configuration artificial atom, which is realized using superconducting quantum circuits (SQCs). There exists a cyclic transition structure due to the broken mirror symmetry, in which three microwave fields are simultaneously applied to drive the corresponding atomic transitions. We find that the microwave fluorescence photons can be emitted on exact one-, two- and three-photon resonance conditions. This is different from natural atom, in which the fluorescence is completely quenched due to dark-state resonance. More interestingly, it is noted that the suppression or enhancement of red (blue) sideband can be controlled by the relative phase of the applied microwave fields. The internal mechanism can be understood based on dressed-state analysis. The phase-sensitive RFS from solid-state devices may find potential application in designing all-optical switch and quantum information processing.

Three-photon laser excitation of mesoscopic ensembles of cold rubidium Rydberg atoms

The spectra of three-photon laser excitation (according to the 5S1/2 → 5P3/2 → 6S1/2 → 37P3/2 scheme) of mesoscopic ensembles of cold Rb Rydberg atoms in a magneto-optical trap, using cw single-frequency lasers in each stage, have been investigated. The ensembles consisted of 1 to 5 atoms, and their presence was recorded by the selective field ionisation method with postselection according to the number of atoms. The dependence of the spectral shape on the excitation laser pulse duration has been studied. For 2-μs pulses, the minimum spectral width was found to be 1.3 MHz; it was determined by the laser linewidth and the spectral width of laser pulse. For pulses shorter than 0.5 μs, additional spectral broadening and occurrence of Rabi oscillations in the wings of three-photon resonances have been observed, a fact indicative of implementation of coherent three-photon laser excitation of Rydberg atoms. An analysis of the spectra within the four-level theoretical model based on optical Bloch equations showed good agreement between the experimental and theoretical results. The dependence of the shape of three-photon excitation spectrum on the number of recorded atoms was also studied. An increase in the average number of atoms leads to the occurrence of a dip in the single-atom excitation spectra; this dip is due to the specificity of the excitation and detection statistics of Rydberg atoms. The results obtained are important for applications of Rydberg atoms in quantum informatics.

Photoelectron circular dichroism in the multiphoton ionization by short laser pulses. II. Three- and four-photon ionization of fenchone and camphor.

Angle-resolved multiphoton ionization of fenchone and camphor by short intense laser pulses is computed by the time-dependent single center method. Thereby, the photoelectron circular dichroism (PECD) in the three-photon resonance enhanced ionization and four-photon above-threshold ionization of these molecules is investigated in detail. The computational results are in satisfactory agreement with the available experimental data, measured for randomly oriented fenchone and camphor molecules at different wavelengths of the exciting pulses. We predict a significant enhancement of the multiphoton PECD for uniaxially oriented fenchone and camphor.

Stimulated emission from ladder-type two-photon coherent atomic ensemble.

We investigated the stimulated emission from a ladder-type two-photon coherent atomic ensemble, for the 5S1/2 - 5P3/2 - 5D5/2 transition of 87Rb atoms. Under the ladder-type two-photon resonance condition obtained using pump and coupling lasers, we observed broad four-wave mixing (FWM) light stimulated from two-photon coherence induced by the seed laser coupled between the ground state of 5S1/2 and the first excited state of 5P3/2. A dip in the FWM spectrum was obtained for three-photon resonance due to V-type two-photon coherence using the pump and seed lasers. From the FWM spectra obtained for varying frequency detuning and seed-laser power, we determined that the seed laser acts as a stimulator for FWM generation, but also acts as a disturber of FWM due to V-type two-photon coherence.

Analysis of high-efficiency widely-tunable N-resonances in Cs vapor

The narrow-band coherent N-type resonance, promising for the development of advanced atomic clocks, can be considered as a type of three-photon resonance, where a two-photon Raman excitation is combined with a resonant optical pumping field. In this communication, we present an experimental study and a theoretical analysis related to three-photon, bi-chromatic excitation of Cs atomic vapor contained in an 8-mm long cell with 20 Torr of neon. If a coupling laser is fixed at a frequency that is lower by several GHz than the position of the absorption profile of the Fg = 4 set of transitions, and a probe laser is tuned over the D2 line (λ = 852 nm), a narrow high-contrast enhanced absorption N-resonance will be observed in the probe light profile, superimposed on the absorption profile of the Fg = 4 set of transitions. We present theoretical modeling aimed to clarify the processes behind the efficiency of the N-resonance preparation for different frequency positions of the coupling laser within the D2 line of Cs.

Higher-order squeezing and entanglement of harmonic oscillators in superconducting circuits

We show that it is possible to obtain higher-order squeezing and entanglement between a pair of harmonic oscillators coupled to a single Δ-type artificial atom, which is realized because of the broken mirror symmetry of the effective potential in the superconducting circuits. Under the three-photon resonance and adiabatic conditions, the system can act as a coherence-controlled atomic reservoir, resulting in the generation of higher-order nonclassicality at steady state. The stable higher-order nonclassical correlations of the two harmonic oscillators in this solid-state device may find potential applications in quantum communications.

Laser-induced dissociative ionization of H2 from the near-infrared to the mid-infrared regime

We apply the Monte Carlo Wave Packet (MCWP) approach to investigate the kinetic energy release (KER) spectra of the protons following double ionization in H$_{2}$ when interacting with laser pulses with central wavelengths ranging from the near-IR (800 nm) to the mid-IR (6400 nm) regions and with durations of 3-21 laser cycles. We uncover the physical origins of the peaks in the nuclear KER spectra and ascribe them to mechanisms such as ionization following a resonant dipole transition, charge-resonance-enhanced ionization (CREI) and ionization in the dissociative limit of large internuclear distances. For relatively large pulse durations, i.e., for 15 or more laser cycles at 3200 nm and 10 or more at 6400 nm, it is possible for the nuclear wave packet in H$_{2}^{+}$ to reach very large separations. Ionization of this part of the wave packet results in peaks in the KER spectra with very low energies. These peaks give direct information about the dissociative energy in the $2p\sigma_{u}$ potential energy curve of H$_{2}^{+}$ at the one- and three-photon resonances between the $2p\sigma_{u}$ and $1s\sigma_{g}$ curves in H$_{2}^{+}$. With the MCWP approach, we perform a trajectory analysis of the contributions to the KER peaks and identify the dominant ionization pathways. Finally, we consider a pump-probe scheme by applying two delayed pulses to track the nuclear dynamics in a time-resolved setting. Low-energy peaks appear for large delays and these are used to obtain the $2p\sigma_{u}$ dissociative energy values at the one-photon resonance between the $2p\sigma_{u}$ and $1s\sigma_{g}$ curves in H$_{2}^{+}$ for different wavelengths.

Third-order terahertz response of gapped, nearly-metallic armchair graphene nanoribbons

We use time dependent perturbation theory to study the terahertz nonlinear response of gapped intrinsic and extrinsic nearly-metallic armchair graphene nanoribbons of finite length under an applied electric field. Generally, the nonlinear conductances exhibit contributions due to single-photon, two-photon, and three-photon processes. The interference between each of these processes results in remarkably complex behavior for the third-order conductances, including quantum dot signatures that should be measurable with a relatively simple experimental configuration. Notably, we observe sharp resonances in the isotropic third-order response due to the Van Hove singularities in the density of states at one-, two-, and three-photon resonances. However, these resonances are absent in the anisotropic third-order response; a result of the overall symmetry of the system.

Optical bistability and multistability via quantum coherence in chiral molecules.

The optical bistability (OB) and multistability (OM) in chiral molecules are investigated by placing the sample into a unidirectional ring cavity. Because of broken mirror symmetry of the effective potential, the chiral molecules have a cyclic three-level Δ-configuration structure, in which one- and two-photon transitions can coexist. We find that the OB is achievable in this system on exact one-, two- and three-photon resonance conditions but absent in the three-level Λ-type system under the two-photon resonance. Moreover, the OM and the switching between OB and OM are also realized by choosing parameters properly. Interestingly, the left- and right-handed chiral molecules exhibit different bistable and multistable behaviors. It is shown that the threshold intensity of OB is strongly dependent on the percentage of the two enantiomers in the mixture. This provides an effective approach to probe molecular chirality and to determine enantiomer excess, which may find potential application in organic chemistry, pharmacology, biochemistry, etc..

Condition for Doppler-free three-photon resonance in a ladder-type atomic system.

We report the essential condition for three-photon electromagnetically induced absorption (TPEIA) in a Doppler-broadened ladder-type atomic system. When the two coupling lasers operate at different frequencies, we observed Doppler-free TPEIA resonance at a counterintuitive frequency, which is the almost half-frequency detuning of the frequency difference between the two coupling fields. Considering three-photon coherence in a Doppler-broadened ladder-type three-level atomic system, the TPEIA due to the atomic group of non-zero velocity was in good agreement with the calculated TPEIA spectrum under the one-photon resonance condition of all three optical fields. From the results, we found that an atomic group with a proper velocity for ladder-type TPEIA should satisfy the one-photon resonances of all three optical fields.

Electron spectroscopy of strontium in the vicinity of the four-photon-excited 5p2 1S0 state

We report on an electron energy analysis study conducted for the purpose of elucidating the single and double ionization pathways when ground state strontium atoms interact with dye laser pulses of ≈5 ns duration, ≈4 × 1011 W cm−2 maximum intensity and 715–737 nm wavelength range. Within this range there are three-photon resonant, four-photon ionized bound states and the four-photon excited 5p 2 1S0 highly correlated autoionizing state, located above the first ionization threshold of strontium. Electron spectra as a function of laser wavelength probed the accumulation of population in the excited 4d j and 5p j Sr+ states. This observation signifies the absorption of at least two photons above the first ionization threshold. However, contrary to what was anticipated in earlier work (performed using the present excitation and ionization scheme but without electron detection) the former states are found to be much more heavily populated than the latter ones. Thus, multi-photon ionization out of the 4d 3/2,5/2 levels of Sr+ and within the same laser pulse is identified as the main pathway to double ionization. Finally, the recording of photoelectron angular distributions from four-photon ionization for selected laser wavelengths revealed the dominant contributing partial waves.

Three-photon resonance and adiabatic passage in the large-detuning Rabi model

We investigate theoretically the quantum Rabi model in the large-detuning regime. When the frequency of the cavity field is near one-third of the atomic transition frequency, we show that there exists a resonant three-photon coupling via intermediate states connected by counter-rotating processes. We derive an effective Hamiltonian of the three-photon coupling, which determines the magnitude of the energy splitting and the position of the resonance analytically. In addition, we present a scheme of three-photon generation based on adiabatic passage across the resonance.

Three-photon resonance ionization of atomic Mn in a hot-cavity laser ion source using Ti:sapphire lasers

Three-photon resonance ionization of atomic manganese (Mn) in a hot-cavity ion source using Ti:sapphire lasers has been demonstrated. Three-step ionization schemes employing different intermediate levels and Rydberg or autoionizing (AI) states in the final ionization step are established. Strong AI resonances were observed via the 3d54s5s f 6S5/2 level at 49 415.35 cm−1, while Rydberg transitions were reached from the 3d54s4d e 6D9/2,7/2,5/2 levels at around 47 210 cm−1. Analyses of the strong Rydberg transitions associated with the 3d54s4d e 6D7/2 lower level indicate that they belong to the dipole-allowed 4d → nf 6F°9/2,7/2,5/2 series converging to the 3d54s 7S3 ground state of Mn II. From this series, an ionization potential of 59 959.56 ± 0.01 cm−1 is obtained for Mn. At high ion source temperatures the semi-forbidden 4d → nf 8F°9/2,7/2,5/2 series was also observed. The overall ionization efficiency for Mn has been measured to be about 0.9% when using the strong AI transition in the third excitation step and 0.3% when employing an intense Rydberg transition. Experimental data indicate that the ionization efficiency was limited by the interaction of Mn atoms with ion source materials at high temperatures.

Mid-infrared optical nonlinearities of chalcogenide glasses in Ge-Sb-Se ternary system.

Optical nonlinearities of chalcogenide glasses in the Ge-Sb-Se ternary system are investigated at mid-infrared wavelengths (2000 and 2500 nm) with femtosecond Z-scan technique. Strong nonlinear refraction in the chalcogenide glasses is observed at 2000 nm, due to three-photon absorption resonance. In addition, the variation in the nonlinear refraction (γ) of the Ge-Sb-Se glasses shows two jumpoints as mean co-ordination number (MCN) approaches 2.4 or 2.7, consistent with the theoretical predication.

Hybrid spin-microcantilever sensor for environmental, chemical, and biological detection

Nowadays hybrid spin-micro/nanomechanical systems are being actively explored for potential quantum sensing applications. In combination with the pump-probe technique or the spin resonance spectrum, we theoretically propose a realistic, feasible, and an exact way to measure the cantilever frequency in a hybrid spin-micromechanical cantilever system which has a strong coherent coupling of a single nitrogen vacancy center in the single-crystal diamond cantilever with the microcantilever. The probe absorption spectrum which exhibits new features such as mechanically induced three-photon resonance and ac Stark effect is obtained. Simultaneously, we further develop this hybrid spin-micromechanical system to be an ultrasensitive mass sensor, which can be operated at 300 K with a mass responsivity 0.137 Hz ag−1, for accurate sensing of gaseous or aqueous environments, chemical vapors, and biomolecules. And the best performance on the minimum detectable mass can be in vacuum. Finally, we illustrate an in situ measurement to detect Angiopoietin-1, a marker of tumor angiogenesis, accurately with this hybrid microcantilever at room temperature.

Four-wave parametric amplification in semiconductor quantum dot-metallic nanoparticle hybrid molecules.

We study theoretically four-wave parametric amplification arising from the nonlinear optical response of hybrid molecules composed of semiconductor quantum dots and metallic nanoparticles. It is shown that highly efficient four-wave parametric amplification can be achieved by adjusting the frequency and intensity of the pump field and the distance between the quantum dot and the metallic nanoparticle. Specifically, the induced probe-wave gain is tunable in a large range from 1 to 1.43 × 10⁵. This gain reaches its maximum at the position of three-photon resonance. Our findings hold great promise for developing four-wave parametric oscillators.

New even-parity high-lying levels of Sm I and measurement of isotope shifts by two-color resonance ionization mass spectrometry

In this work, we investigate the even-parity high-lying levels of Sm I in the energy region 33136–33960cm−1 by performing two-color three-photon resonance ionization spectroscopy in an atomic beam coupled to a time-of-flight mass spectrometer using two tunable pulsed dye lasers. We observe twenty-one new and confirm eight previously reported even-parity energy levels of Sm I in this spectral region. Absolute energies of these levels are determined with an accuracy of ±0.3cm−1. Using electric dipole selection rule, total angular momentum (J-value) of the most newly observed levels is assigned uniquely. Further, employing two-color three-step resonance ionization mass spectrometry, we measure the isotope shift between 154Sm and 144Sm of sixteen high-lying levels with a moderate accuracy of ±30mK.

Enhancement of the single-colour three-photon resonance spectroscopy of highly excited states of the samarium atom

Enhancement of the single-colour three-photon resonance spectroscopy of highly excited states of the samarium atom

Atomic wave-packet dynamics and third-harmonic generation in sodium

In femtosecond degenerate four-wave mixing experiments in sodium vapor, quantum beats are observed at the wavelength of the third harmonic when the fundamental beams are three-photon resonant. The period of beating, which corresponds to fine structure energy-level splitting, does not change with the atomic number density, buffer gas pressure, or laser intensity. Surprisingly, the third-harmonic signal is observed only at negative time delays for the transient grating pulse sequence. We relate this to the well-known interference effect between excitation pathways involving the fundamental and the third-harmonic fields, which leaves atoms virtually unexcited and prevents formation of population grating.

Coherent internal state transfer by a three-photon STIRAP-like scheme for many-atom samples

A stimulated Raman adiabatic passage (STIRAP)-like scheme is proposed to exploit a three-photon resonance taking place in alkaline-earth-metal ions. This scheme is designed for state transfer between the two fine structure components of the metastable D-state which are two excited states that can serve as optical or THz qubit. The advantage of a coherent three-photon process compared to a two-photon STIRAP lies in the possibility of exact cancellation of the first-order Doppler shift which opens the way for an application to a sample composed of many ions. The transfer efficiency and its dependence with experimental parameters are analysed by numerical simulations. This efficiency is shown to reach a fidelity as high as (1–8 × 10−5) with realistic parameters. The scheme is also extended to the synthesis of a linear combination of three stable or metastable states.