High-order harmonic generation (HHG) has become an indispensable process for generating attosecond pulse trains and single attosecond pulses used in the observation of nuclear and electronic motion. As such, improved control of the HHG process is desirable, and one such possibility for this control is through the use of structured laser pulses. We present numerical results from solving the one-dimensional time-dependent Schrödinger equation for HHG from hydrogen using Airy and Gaussian pulses that differ only in their spectral phase. Airy pulses have identical power spectra to Gaussian pulses, but different spectral phases and temporal envelopes. We show that the use of Airy pulses results in less ground state depletion compared to the Gaussian pulse, while maintaining harmonic yield and cutoff. Our results demonstrate that Airy pulses with higher intensity can produce similar HHG spectra to lower intensity Gaussian pulses without depleting the ground state. The different temporal envelopes of the Gaussian and Airy pulses lead to changes in the dynamics of the HHG process, altering the time-dependence of the ground state population and the emission times of the high harmonics.
High-order harmonic generation (HHG) using an Airy pulse with a third order spectral phase results in less ground state depletion, but similar harmonic yield, compared to a Gaussian pulse. Top – schematic depiction of the 3-step HHG process for different intensity pulses. Bottom left – time-dependent ground state populations for Gaussian pulses showing that a more intense pulse causes more ground state depletion. Bottom middle – final ground state populations for Airy and Gaussian pulses as a function of intensity showing that Airy pulses result in less ground state depletion for a given intensity. Bottom right – HHG spectra for a more intense Airy pulse and a less intense Gaussian pulse exhibit similar shapes, magnitudes, and plateau cutoff values
The dynamics of hyperbolic secant beams under the competition between the fractional diffraction and rectangular potential is investigated. It is found that the beams can exhibit the reflection, tunneling and interference, forming the bound states, optical lattices or fringes, or solitons under different conditions. In linear regime, when the potential is wide, the beam exhibits the total reflection for deeper potential and smaller incident angle, and presents the reflection and tunneling for shallower potential and larger incident angle. The irregular interference pattern and bound states are generated for the narrow potential. Moreover, the initial chirp causes the appearance of side lobes during beam propagation. When two hyperbolic secant beams are symmetrically incident from inside or outside the potential, the interference lattices or interference fringes are generated inside the potential, which are related to the Lévy index, initial chirp and incident angle of the beams. In nonlinear regime, the hyperbolic secant beam undergoes the collapse, splitting or formation of the periodic-like soliton by selecting appropriate parameters including the Lévy index, initial chirp and incident angle. In addition, the dynamics of two hyperbolic secant beams under the interaction of the nonlinear effect and fractional diffraction is also investigated in detail. This work provides more possibilities for optical lattice generation and optical manipulation.
Most of the previously proposed methods for nonreciprocal light transmission are based on the unequal couplings of the nanocavity with the input waveguide and the output waveguide, which will inevitably affect the contrast ratio and working bandwidth. Here, we present a simple approach just via the side coupling between one nonlinear resonator and a coupling-tunable waveguide, demonstrating that a high transmission contrast, broad operation bandwidth, and controllable nonreciprocal light transmission can be realized even though the coupling is symmetric. The underlying physics is revealed. This approach may open a way for the study of on-chip optical information processing and quantum computing.
Reconfigurable nonreciprocal light transmission with high contrast and broad operation bandwidth
With the aim of providing datasets for simulations of electron transport processes in the upper atmosphere, we measured singly differential elastic electron scattering and doubly differential electron-impact ionization cross sections of nitrous oxide. These measurements were conducted for primary electron energies between 30 eV and 1 keV in the angular range of 20°–150°. Secondary electron energies spanned from 4 eV to approximately half of the primary electron energy. In addition to the measurements, the differential elastic scattering cross sections of nitrous oxide were calculated using the IAM-SCAR + I model. Furthermore, the singly differential and total ionization cross sections of nitrous oxide were obtained by integrating the doubly differential ionization cross sections over emission angle and over both emission angle and secondary electron energy, respectively. These cross sections were compared to calculations performed using the BEB model and to experimental results of other groups, who determined the total ionization cross sections of nitrous oxide by collecting ions generated during electron impact.
Solar physicists routinely utilize observations of Ar-like Fe IX and Cl-like Fe X emission to study a variety of solar structures. However, unidentified lines exist in the Fe IX and Fe X spectra, greatly impeding the spectroscopic diagnostic potential of these ions. Here, we present measurements using the Lawrence Livermore National Laboratory EBIT-I electron beam ion trap in the wavelength range 238–258 Å. These studies enable us to unambiguously identify the charge state associated with each of the observed lines. This wavelength range is of particular interest because it contains the Fe IX density diagnostic line ratio 241.74 Å/244.91 Å, which is predicted to be one of the best density diagnostics of the solar corona, as well as the Fe X 257.26 Å magnetic-field-induced transition. We compare our measurements to the Fe IX and Fe X lines tabulated in CHIANTI v10.0.1, which is used for modeling the solar spectrum. In addition, we have measured previously unidentified Fe X lines that will need to be added to CHIANTI and other spectroscopic databases.
We present a two-state Kalman estimator of gravity acceleration and evaluate its performance by numerical simulations and post-measurement demonstration with real-world atomic gravimetry. We show that the estimator-enhanced gravimetry significantly improves upon both short-term sensitivity and long-term stability. The estimates of gravity acceleration demonstrate a (tau ^{1/2}) feature well under white phase noise in the short term, and continue to improve as (tau ^{-1/2}) or improve faster as (tau ^{-1}) in the long term. This work validates the estimation of gravity acceleration as a key topic for future atomic gravimetry.
The performance of atomic gravimetry is limited by noises and other systematic or geophysical effects. By building a Kaman estimator rooted in the physics of atom interferometry, we realize significant improvements in both short-term sensitivity and long-term stability. This demonstration of estimator-enhanced gravimetry would be of great interest for static measurements of gravity, such as metrology or geophysics (Color online)
Creating non-Gaussian photonic states in the continuous variable regime, with high fidelity is essential for implementing universal quantum computation. However, this is a challenging task to achieve the essential nonlinearity. Alternatively, various non-Gaussian states of light can be created by the use of a simple linear setup called quantum optical catalysis (QOC). In this work, we attempt to bring out the salient features of the multi-photon QOC process in terms of state preparation and characterization. The notion of state preparation from the QOC is achieved by expressing the output state as displaced qudits (DQ). The obtained superposition coefficients facilitate the characterization of states and carve a path to get desired non-Gaussian states. Moreover, the figures of merit of the prepared states are employed through Hilbert Schmidt distance, Wigner negativity, and quadrature squeezing. From the results, it is inferred that the creation of individual displaced number states plays a predominant role in non-Gaussianity among the states derived. Meanwhile, the superposition of number states remains effective in achieving a significant degree of squeezing. In addition, the non-ideal preparation of DQ under realistic experimental conditions is investigated by incorporating imperfect photon detectors and mixed photon sources. The calculated success probability also attests to the potential for state generation.
In quantum phase estimation, the Heisenberg limit provides the ultimate accuracy over quasi-classical estimation procedures. However, realizing this limit hinges upon both the detection strategy employed for output measurements and the characteristics of the input states. This study delves into quantum phase estimation using s-spin coherent states superposition. Initially, we delve into the explicit formulation of spin coherent states for a spin (s=3/2). Both the quantum Fisher information and the quantum Cramer–Rao bound are meticulously examined. We analytically show that the ultimate measurement precision of spin cat states approaches the Heisenberg limit, where uncertainty decreases inversely with the total particle number. Moreover, we investigate the phase sensitivity introduced through operators (e^{izeta {S}_{z}}), (e^{izeta {S}_{x}}) and (e^{izeta {S}_{y}}), subsequently comparing the resultants findings. In closing, we provide a general analytical expression for the quantum Cramér–Rao bound applied to these three parameter-generating operators, utilizing general s-spin coherent states. We remarked that attaining Heisenberg-limit precision requires the careful adjustment of insightful information about the geometry of s-spin cat states on the Bloch sphere. Additionally, as the number of s-spin increases, the Heisenberg limit decreases, and this reduction is inversely proportional to the s-spin number.
A three-color three-step resonance ionization mass spectroscopy technique was explored to investigate the odd-parity autoionization states of atomic lutetium, covering a range from 51,850 to 55,000 cm−1. By applying Fano fitting to the spectral analysis, we successfully identified 98 autoionization states, with 69 of which had never been reported. We also determined the half-width and transition strength for all identified states. Additionally, the lifetime of the excited state at 36,769.25 cm−1 was measured. This work provides the most comprehensive dataset to date on the complex odd-parity autoionization states of atomic lutetium, offering essential insights for enhancing the efficiency of resonant photoionization processes and understanding the atomic autoionization structure of lutetium.
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