Transition Wavelengths Research Articles

Laser measurements of static and dynamic dipole polarizability for 11 metal atoms using fast exploding wires in vacuum and integrated-phase technique

The rapid electrical explosion of thin metal wires in a vacuum can completely vaporize the wire and form a fast-expanding gas cylinder of metal atoms. Thin metal wires 12.7 μm in diameter made of W, Mo, Pt, Pd, Ni, Cu, Au, and Al completely evaporated during the first ∼10 ns under the action of a fast-rising current of ∼1 kA/ns. Laser interferometry and the integrated phase technique were used to reconstruct the dynamic atomic polarizability for fully vaporized thin metal wires at 532 and 1064 nm wavelength, calculate the static atomic polarizability, the first dipole-allowed electronic transition energy, and transition wavelengths, and compare our reconstructions with available tabulated values.

Frequency Conversion Interface towards Quantum Network: From Atomic Transition Line to Fiber Optical Communication Band

Quantum repeater is a key component of quantum network, and atomic memory is one of the important candidates for constructing quantum repeater. However, the atomic transition wavelength is not suitable for long-distance transmission in optical fiber. To bridge atomic memory and fiber communication, we demonstrate a frequency conversion interface from rubidium D1 line (795 nm) to the optical communication L-band (1621 nm) based on difference frequency generation. To reduce broadband noise of spontaneous Raman scattering caused by strong pumping light, we use a combination of two cascaded etalons and a Fabry-Perot cavity with low finesse to narrow the noise bandwidth to 11.7 MHz. The filtering system is built by common optical elements and is easy to use; it can be widely applied in frequency conversion process. We show that the signal-noise ratio of the converted field is good enough to reduce the input photon number below 1 under the condition of low external device conversion efficiency (0.51%) and large duration of input pulse (250 ns). The demonstrated frequency conversion interface has important potential application in quantum networks.

Energies and transition data for Be-like hafnium and tantalum ions

Energies and lifetimes of the lowest 178 levels belonging to the 1s22s2,1s22s2p,1s22p2,1s22snl, and 1s22pnl(n=3−6;l=0−5) configurations in Be-like hafnium and tantalum ions (Hf LXIX and Ta LXX) have been computed, as well as transition wavelengths, transition probabilities, line strengths, and weighted oscillator strengths of the electric/magnetic dipole (E1/M1) and electric/magnetic quadrupole (E2/M2) transitions between these levels. The calculations have been carried out using the GRASP2018 code through the multiconfiguration Dirac–Hartree–Fock (MCDHF) method with the Breit interaction and quantum electrodynamics (QED) corrections. The present results have been compared with previous data. Furthermore, the values of the last two active sets were compared to estimate the accuracy.

Theoretical analysis of atomic parameters of Sm-like and Nd-like W ions in soft x-ray region

We calculated atomic data such as energy levels, transition wavelengths, oscillator strengths and transition rates for Sm-like and Nd-like W ions. We employed flexible atomic code (FAC) in our computations. We computed fine structure levels of configurations 4f125s2, 4f125s5p and 4f135s for Nd-like W and configurations 4f145s2, 4f135s25p and 4f125s25p2 for Sm-like W. We have provided transition data of electric dipole (E1) transitions and magnetic quadrupole (M2) transitions for transition 4f125s2—4f125s5p and magnetic dipole (M1) and electric quadrupole (E2) transition data for transition 4f145s2 − 4f125s25p2. We also found that spectral lines of these transitions in Sm and Nd-like W ion spectra lie in soft x-ray (SXR) region. We compared transition data of Nd-like W and excitation energies of Sm-like W ions with available theoretical and experimental results. We also discussed the effect of configuration interaction on atomic data of Nd-like W and excitation energies of Sm-like W by systematically increasing the number of configurations.

Semiconductor-dielectric-metal solar absorbers with high spectral selectivity

An ideal solar thermal absorber has a sharp transition between high and low absorptance at the wavelength where the blackbody emissive power begins to exceed the solar irradiance. However, most real selective absorbers have a fairly broad transition, leading to both solar absorption and thermal emission losses. Here, we model, fabricate, and characterize a highly selective semiconductor-dielectric-metal (Ga0.46In0.54As - MgF2 - Ag) solar absorber with an extremely sharp transition from high to low absorptance. The thin semiconductor serves as a selective filter, absorbing photons with wavelengths shorter than the bandgap and transmitting those with longer wavelengths. The highly reflective dielectric-metal rear mirror allows the structure to have very low emittance for longer wavelengths. These characteristics provide the absorber with a measured solar absorptance >91% below the bandgap wavelength and infrared emittance <5% at 100 C above the bandgap wavelength. This transition wavelength can be tuned by modifying the semiconductor composition, and modeling indicates that the absorber's optical properties should be stable at high temperatures, making the structure a good candidate for unconcentrated to highly concentrated solar thermal energy conversion.

Photoionization cross sections of ultracold 88Sr in 1P1 and 3S1 states at 390 nm and the resulting blue-detuned magic wavelength optical lattice clock constraints.

We present the measurements of the photoionization cross sections of the excited 1P1 and 3S1 states of ultracold 88Sr atoms at 389.889 nm wavelength, which is the magic wavelength of the 1S0-3P0 clock transition. The photoionization cross section of the 1P1 state is determined from the measured ionization rates of 88Sr in the magneto-optical trap in the 1P1 state to be 2.20(50)×10-20 m2, while the photoionization cross section of 88Sr in the 3S1 state is inferred from the photoionization-induced reduction in the number of atoms transferred through the 3S1 state in an operating optical lattice clock to be 1.38(66) ×10-18 m2. Furthermore, the resulting limitations of employing a blue-detuned magic wavelength optical lattice in strontium optical lattice clocks are evaluated. We estimated photoionization induced loss rates of atoms at 389.889 nm wavelength under typical experimental conditions and made several suggestions on how to mitigate these losses. In particular, the large photoionization induced losses for the 3S1 state would make the use of the 3S1 state in the optical cycle in a blue-detuned optical lattice unfeasible and would instead require the less commonly used 3D1,2 states during the detection part of the optical clock cycle.

First example of vinylbenzene based small photovoltaic molecules: Towards the development of efficient D-π-A configured optoelectronic materials for bulk heterojunction solar cells

Making contribution to the development of novel photovoltaic materials for solar cell applications, we rationally developed six novel vinylbenzene based planar donor-π-acceptor (D-π-A) compounds. Optoelectronic properties of developed molecules are determined using frontier molecular orbital (FMO), UV–Visible, density of state (DOS), transition density matrix (TDM) heat map, open circuit voltage (Voc), binding energies (E b ), reorganization energy of electron ( λ e ), hole ( λ h ), charge transfer analysis and compared with reference DVB-T-ID. Donor group modifications effectively contributed to augment photovoltaic features in all developed compounds. Developed molecules are found with reduced energy gap (2.566–1.805 eV), broaden absorption wavelength (548.09–800.36 nm) and small transition energy (2.262–1.549 eV) as compared to reference DVB-T-ID values 2.819 eV, 492.84 nm and 2.515 eV respectively. The developed molecules have proficient hole and electron transfer mobilities and can serve as best candidate when blended with PC 61 BM film. Optoelectronic features of all developed molecules especially D5 is ascertained eye-catching as compared to DVB-T-ID , hence recommended for future solar cell applications. • Six vinylbenzene based planar D-π-A photovoltaic compounds are designed by donor group modifications. • The optoelectronic properties were studied in detail using DFT and TDDFT calculations. • FMO, UV–Visible, DOS, ODOS, TDM, Voc, reorganization energy of electron and hole, binding energy and charge transfer analysis are performed. • All vinylbenzene based investigated molecules exhibited remarkable optoelectronic properties. • Investigated molecules are recommended for future solar cell applications.

Dilute-As InGaNAs/GaN Quantum Wells for High-Efficiency Red Emitters

The dilute-As InGaNAs-based quantum well (QW) active region and the corresponding large-overlap design is analyzed by using a self-consistent 6-band <inline-formula> <tex-math notation="LaTeX">$k\cdot p$ </tex-math></inline-formula> method. Our study evaluates the optical transition energy, ground state electron-hole wavefunction overlap, and optical gain characteristics of a dilute-As InGaNAs QW consisting of a 3.3 nm thick In_0.19Ga_0.81N_0.94As_0.06 well and 10 nm thick GaN barriers. The calculation suggests that the In_0.19Ga_0.81N_0.94As_0.06 QW may result in a transition wavelength and optical gain comparable to a conventional 3.3 nm thick In_0.35Ga_0.65N QW, while preserving low In-content (&#x007E;19&#x0025;). In addition, a staggered dilute-As InGaNAs QW design with a modulated As-doping profile in the InGaNAs QW is presented, and the calculation results in a significantly enhanced wavefunction overlap and optical gain. This study reveals the excellent potential of the dilute-As InGaNAs semiconductor for application as a high efficiency active region material for future long wavelength emitters.

Converting single photons from an InAs/GaAs quantum dot into the ultraviolet: preservation of second-order correlations

Wavelength conversion at the single-photon level is required to forge a quantum network from distinct quantum devices. Such devices include solid-state emitters of single or entangled photons, as well as network nodes based on atoms or ions. Here we demonstrate the conversion of single photons emitted from a III-V semiconductor quantum dot at 853 nm via sum frequency conversion to the wavelength of the strong transition of Yb+ ions at 370 nm. We measure the second-order correlation function of both the unconverted and the converted photon and show that the single-photon character of the quantum dot emission is preserved during the conversion process.

Benchmarking calculations of wavelengths and transition rates with spectroscopic accuracy for W xlviii through W lvi tungsten ions

Atomic properties of $n=3$ levels for ${\mathrm{W}}^{47+}\ensuremath{-}{\mathrm{W}}^{55+}$ ions ($Z=74$) are systematically calculated using two different and independent methods, namely, the second-order many-body perturbation theory and the multiconfiguration Dirac-Hartree-Fock method combined with the relativistic configuration interaction approach. Wavelengths and transition rates for electric- and magnetic-dipole transitions involving the $n=3$ levels of ${\mathrm{W}}^{47+}\ensuremath{-}{\mathrm{W}}^{55+}$ are calculated. In addition, we discuss in detail the importance of the valence and core-valence electron correlations, the Breit interaction, the higher-order frequency-dependent retardation correction, and the leading quantum electrodynamical corrections for transition wavelengths. Spectroscopic accuracy is achieved for the present calculated wavelengths, and most of them agree with experimental values within $0.05%$. Our calculated wavelengths, combined with collisional radiative model simulations, are used to identify the yet unidentified 25 observed lines in the extremely complex spectrum between $27\phantom{\rule{0.16em}{0ex}}\AA{}$ and $34\phantom{\rule{0.16em}{0ex}}\AA{}$ measured by Lennartsson $et\phantom{\rule{4pt}{0ex}}al.$ [Phys. Rev. A 87, 062505 (2013)]. We provide additional data for 472 strong electric-dipole transitions in the wavelength range of 17--50 \AA{}, and 185 strong magnetic-dipole transitions between $36\phantom{\rule{0.16em}{0ex}}\AA{}$ and $4384\phantom{\rule{0.16em}{0ex}}\AA{}$, with a line intensity greater than $1\phantom{\rule{0.16em}{0ex}}\mathrm{photon}/\mathrm{s}$. These can provide benchmark data for future experiments and theoretical calculations.

Single-cycle-pulse generation in a coherently mode-locked laser with an ultrashort cavity

We theoretically investigate the possibility of a passive mode-locking regime in a two-section laser with an ultrashort cavity of the length around ten wavelengths of the medium resonant transition or even less. It is shown that such a regime is enabled through the coherent mode-locking phenomena arising due to the self-induced transparency when the gain and absorption bandwidths do not impose any restrictions on the duration of the generated pulse. Under such conditions, a laser with an ultrashort cavity could produce output pulses with the terahertz (THz) repetition rate and the duration up to a single optical cycle. Moreover, several scaling rules were derived, which allow for further shortening of the output pulse duration with the respective scaling of the media parameters.

Enhanced Amplification of Attosecond Pulses in a Hydrogen-like Plasma-Based X-ray Laser Modulated by an Infrared Field at the Second Harmonic of Fundamental Frequency

In a recent work (Antonov et al., Physical Review Letters 123, 243903 (2019)), it was shown that it is possible to amplify a train of attosecond pulses, which are produced from the radiation of high harmonics of the infrared field of the fundamental frequency, in the active medium of a plasma-based X-ray laser modulated by a replica of the infrared field of the same frequency. In this paper, we show that much higher amplification can be achieved using the second harmonic of the fundamental frequency for modulating of a hydrogen-like active medium. The physical reason for such enhanced amplification is the possibility to use all (even and odd) sidebands induced in the gain spectrum in the case of the modulating field of the doubled fundamental frequency, while only one set of sidebands (either even or odd) could participate in amplification in the case of the modulating field of the fundamental frequency due to the fact that the spectral components of the high-harmonic field are separated by twice the fundamental frequency. Using the plasma of hydrogen-like C5+ ions with an inverted transition wavelength of 3.38 nm in the water window as an example, it is shown that the use of a modulating field at a doubled fundamental frequency makes it possible to increase the intensity of amplified attosecond pulses by an order of magnitude in comparison with the previously studied case of a fundamental frequency modulating field.

Generation and catalysis of coherence with scalar fields

Recently it has been demonstrated that it is possible to harvest quantum resources other than entanglement from a coherent scalar field. Employing time-dependent perturbation theory, we present a complete analysis of the conditions under which a spatially extended Unruh-DeWitt detector coupled to the proper time derivative of the field can harvest coherence for any initial state of the field, as well as the energy cost that is required for each harvest. By studying harvesting under repeatable extractions it is proven that when the detector interacts with the field through a delta coupling coherence is catalytic. For a Gaussian smeared detector it is shown that harvesting from a coherent field depends on the phase of its amplitude distribution and its initial energy as well as on the mean radius of the detector and the mean interaction duration between the two. For a detector moving at a constant velocity and with a mean radius of the same order as its transition wavelength, we observe that, for relativistic speeds, coherence swelling effects are present the intensity of which depends on the dimension of the underlying Minkowski spacetime.

Broadband wavelength tuning of electrically stretchable chiral photonic gel

Abstract Chiral photonic-band structure provides technical benefits in the form of a self-assembled helical structure and further functional wavelength tunability that exploits helical deformation according to pitch changes. The stopband wavelength control of the chiral photonic-band structure can be obtained by individual electrical methods or mechanical stretching deformation approaches. However, research on combined electric control of stretchable chiral photonic-band wavelength control while ensuring optical stability during the tuning process has remained limited till now. In this study, using the hybrid structure of elastomeric mesogenic chiral photonic gels (CPGs) with an electrically controlled dielectric soft actuator, we report the first observation of electrically stretchable CPGs and their electro-mechano-optical behaviors. The reliable wavelength tuning of a CPG to a broadband wavelength of ∼171 nm changed with high optical stability and repeated wavelength transitions of up to 100 times. Accordingly, for the first time, electrical wavelength tuning method of stretchable chiral liquid crystal photonicband structure was investigated.

Spectral calibration for electron beam ion trap and precision measurement of M1 transition wavelength in Ar&lt;sup&gt;13+&lt;/sup&gt;

The precise measurement of the transition wavelength of the fine structure of highly charged ions can not only test basic physical theories including the quantum electrodynamics effect and the electronic correlation effect but also provide key atomic data for astrophysics and fusion plasma physics. Furthermore, highly charged ions are considered as a potential candidate for optical clocks with extremely ultra-high precision. In this work, a new spectral calibration system is built in a high-temperature superconducting electron beam ion trap (SH-HtscEBIT) in the Institute of Modern Physics, Fudan University, and the uncertainty of its spectrum wavelength measurement is evaluated by combining internal and external calibrations. The minimum wavelength uncertainty caused by the new spectral calibration system in the visible light band reaches 0.002 nm. On this basis, the precise measurement of 2s&lt;sup&gt;2&lt;/sup&gt;2p &lt;sup&gt;2&lt;/sup&gt;P&lt;sub&gt;1/2&lt;/sub&gt;－&lt;sup&gt;2&lt;/sup&gt;P&lt;sub&gt;3/2&lt;/sub&gt; M1 transition wavelength for boron-like Ar&lt;sup&gt;13+&lt;/sup&gt; is performed at the SH-HtscEBIT by utilizing the new calibration system. The experimentally measured transition wavelength is (441.2567 ± 0.0026) nm. It is currently the experimental result with the highest measurement accuracy of spectroscopy of highly charged ions at the SH-HtscEBIT, which lays the foundation for the precise measurement of the hyperfine splitting and isotope shift of highly charged ions in the future experiments.

Theoretical study of linear and non-linear optical properties of small CaCn (n = 2–7) clusters

The linear and NLO properties of small calcium doped carbon cluster CaCn (n = 2–7) were investigated in the framework of time-dependent density functional theory (TD-DFT) with CAM-B3LYP/6-311+G(d). The absorption wavelength (λ), oscillatory strength (f), transition energy (Eex), and nature of transitions of major excitations have been calculated. It was shown that the most intense peak was fall in the UV region of the spectrum. The most intense peaks among all studied clusters for CaC6was found at 230 nm with oscillatory strength of 0.261, and excitation was due to H-2 → L, H-1 → L + 1, H → L + 13 transition. We observe a few peaks with weaker peaks in the visible region for CaC2, CaC5, and CaC7at560 nm, 525 nm, and 467, respectively. The average polarizability α and first hyperpolarizability βtot have been calculated and found that the polarizability of studied clusters increases with the number of carbon atoms in the cluster. Hyperpolarizability of CaC2 and CaC5 was calculated as 2874.7 a.u. and 1329.9 a.u. Indicating strong NLO prospects among all studied clusters. The optical response of studied clusters suggests that these materials can be considered as auspicious for optoelectronic devices.

Analysis of squeezed light source in band of alkali atom transitions based on cascaded optical parametric amplifiers

The squeezed light field in the band of alkali metal atomic transitions is an important quantum resource in the field of quantum information and precision measurement. The wavelengths of atomic transition lines (760–860 nm) are relatively short. Limited by the gray-tracking effect of nonlinear crystals, the squeezing degree of the squeezed light in this band generated by the optical parametric amplifiers is low. Now, the squeezing is about 3–5 dB. Considering the problems in the experimental generation of the squeezed light at the wavelengths of atomic transitions, the variation law of quantum noise of the light field output from the single optical parametric amplifier with its physical parameters is studied theoretically, and the optimal physical parameters are obtained. To further improve the squeezing in the band of alkali metal atomic transitions, the cascaded optical parametric amplifiers are considered. Based on the basic theory of the optical parametric amplifiers, the theoretical model of the cascaded optical parametric amplifiers is constructed, in which the optical loss and phase noise of the cascaded optical loops are considered. Based on this, the quantum noise characteristics of the light field output from the cascaded system versus the optical loss and phase noise are analyzed at the frequencies of 2 MHz and 100 kHz, respectively. It is found that for the squeezing at 2 MHz, cascading 2 to 3 optical parametric amplifiers can significantly improve the squeezing under the premise of the low optical path loss and phase noise; for the squeezing in the low-frequency band, the enhancement of the squeezing for the cascaded system is quite weak. Under the current experimental parameters, the squeezing at 2 MHz of the squeezed light on rubidium resonance can be improved from –5 dB to –7 dB by cascading another DOPA. For the squeezing at low frequency band, the cascaded system proves to be useless, and the efforts should be made to reduce the technique noise in the low frequency band. Furthermore, the quantum limit and spectral characteristics of the squeezed light field output from the cascaded system are further explored. This study can provide reference and guidance for the improvement in the squeezing degree of the band of atomic transitions.

Негармонические пространственные структуры разности населенностей, создаваемые униполярными прямоугольными импульсами в резонансной среде

In the case of coherent interaction with a medium of extremely short light pulses from a carrier of a harmonic form (when the pulse durations are shorter than the population relaxation times T_1 and polarization T_2 of the medium), electromagnetically induced gratings (EMIGs) of the population difference, which have a pronounced harmonic dependence on the coordinates, may appear in it. These structures can occur when pulses do not overlap at the same time or overlap in the medium. Recently, the possibility of obtaining unipolar electromagnetic pulses of the optical and adjacent ranges of non-harmonic shape, for example, rectangular and triangular, with a duration less than or comparable to the duration of the PCR in this range, has attracted interest. In this work, using the numerical solution of the system of Maxwell-Bloch equations, we study EMIG induced by rectangular attosecond pulses in a two-level resonant medium. The possibility of inducing an EMIG of a non-harmonic form in the form of light-induced channels, a kind of microresonators, with a size of the order of the wavelength of the resonant transition of the medium, whose parameters can be controlled, for example, by the amplitude of the incident pulses, is shown. It has been suggested that it is possible to create an EMIG of a predetermined non-harmonic form only in the general case of using unipolar pulses.

Nonharmonic Spatial Population Difference Structures Created by Unipolar Rectangular Pulses in a Resonant Medium

In the case of coherent interaction with a medium of extremely short light pulses (ESPs) having a carrier frequency and harmonic shape (when the pulse durations are shorter than the population relaxation times T1 and polarization relaxation time T2 of the medium), electromagnetically induced gratings (EMIGs) of the population difference, which have a pronounced harmonic dependence on the coordinates, may appear in it. These structures can occur when pulses do not overlap or overlap in the medium. Recently, the possibility of obtaining unipolar electromagnetic pulses in the optical and adjacent ranges of non-harmonic shape, for example, rectangular and triangular, with a duration less or comparable to the duration of the extremely-short pulse in this range, has attracted interest. In this work, using the numerical solution of the system of Maxwell-Bloch equations, we study EMIG formation by rectangular attosecond pulses in a two-level resonant medium. The possibility of inducing an EMIG of a non-harmonic shape in the form of light-induced channels microresonators, (microcavities) with a size of the order of the wavelength of the resonant transition of the medium, whose parameters can be controlled, for example, by the amplitude of the incident pulses, is shown. It has been suggested that it is possible to create an EMIG of a predetermined non-harmonic shape only in the general case of using unipolar pulses. Keywords: attosecond pulses, unipolar pulses, rectangular pulses, electromagnetically induced gratings, polarization waves, light-induced microresonators.

Magic Wavelengths for 1S–nS and 2S–nS Transitions in Hydrogenlike Systems

We study the magic wavelength for two-photon 1S–nS transitions in a hydrogen and deuterium atom, as well as 2S–nS transitions, where the lower level is the metastable 2S state. At the magic wavelength, the dynamic Stark shifts of the ground and the excited state of the transition coincide, so that the transition frequency is independent of the intensity of the trapping laser field. Experimentally feasible magic wavelengths of transitions with small slopes in the atomic polarizabilities are determined; these are the most stable magic wavelengths against variations of the laser frequency. We provide data for the magic wavelengths for the 1S–nS and 2S–nS transitions in hydrogen and deuterium, with n=2,⋯,8. We also analyze the stability of the elimination of the ac Stark shift at the magic wavelength against tiny variations of the trapping laser frequency from the magic value.