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Utilizing long-wavelength laser diodes (LDs) for pumping to achieve high-power fiber laser output is an effective method for attaining high quantum efficiency and excellent thermal management. In this work, we report on a Master Oscillator Power Amplifier (MOPA)-structured long-tapered Yb3+-doped fiber laser directly pumped by long-wavelength laser diodes. By shifting the center wavelength of the pump source to 1010 nm, the heat generation within the fiber laser is effectively controlled, thereby increasing the transverse mode instability (TMI) threshold. Additionally, the use of a long-tapered fiber enlarges the mode area and suppresses stimulated Raman scattering (SRS) effects that typically arise from increased fiber length. As a result, an output of 6030 W is achieved with an optical-to-optical (O–O) efficiency of 83.7%, a SRS suppression ratio exceeding 50 dB, and no occurrence of dynamic TMI. This approach provides a valuable reference for optimizing long-wavelength pumping to suppress nonlinear effects and also holds potential for wide-temperature operational applications. [ABSTRACT FROM AUTHOR]

Three‐photon‐pumped (3PP) excitonic lasing in inorganic semiconductor quantum dots (QDs) is of particular importance for near‐infrared biophotonics and optical communications. However, the implementation of such lasers has been hindered severely by the required high pump thresholds. Here, 3PP excitonic lasing of all‐inorganic cesium lead bromide perovskite QDs (CsPbBr3 PQDs) embedded in a whispering‐gallery microcavity is demonstrated, and achieving a record low threshold of 3 mJ cm−2 by tuning the 3P pump energy in resonance with the S exciton state. Wavelength‐dispersive Z‐scan spectroscopy reveals that such reduced lasing threshold is attributed to the exciton resonance enhanced multiphoton absorption, which, as disclosed by the kinetics analysis of transient absorption spectroscopy (TAS), leads to the appearance of net gain at a pump fluence as low as 2.2 mJ cm−2, corresponding to an average S exciton population of 1.5. A microscopic model incorporating the quantum master equation reproduces the TAS results and provides the intrinsic parameters of biexciton relaxation for lasing. The 3PP resonant excitonic transition is the most favored multiphoton pumping process that minimizes quantum defect (6.8% of the pump photon energy) to realize optical gain at low threshold, marking a major step toward using all‐inorganic perovskite QDs for on‐chip integrated microlasers and multiphoton bioimaging. [ABSTRACT FROM AUTHOR]

Lithium and lithium-like elements look like hydrogen atoms if their two electrons and the nucleus are considered as having a core around which a single electron is orbiting. The energy and radii expressions for hydrogen atoms can be used for lithium and lithium-like elements; an important modification is introducing an effective principal quantum number. The effective principal quantum number differs from the principal quantum number of hydrogen by the quantum defect. The quantum defect has respective values for various levels of lithium and lithium-like ions. In this study, we used extended Ritz formulas to calculate quantum defects required to calculate the energies of the ns, np, nd, and nf series up to n < 31. Using these energies, we calculated transition probabilities and then the lifetimes of the lithium levels. The lifetimes were compared with the available published data; an excellent agreement was noticed. The work also extended the available list of lifetimes to higher quantum numbers. Forty lifetimes are newly calculated and presented for the first time. A polynomial formula for each of the ns, np, nd, and nf series lifetimes has been developed that fits well the lifetime values. [ABSTRACT FROM AUTHOR]

Utilizing long-wavelength laser diodes (LDs) for pumping to achieve high-power fiber laser output is an effective method for attaining high quantum efficiency and excellent thermal management. In this work, we report on a Master Oscillator Power Amplifier (MOPA)-structured long-tapered Yb3+-doped fiber laser directly pumped by long-wavelength laser diodes. By shifting the center wavelength of the pump source to 1010 nm, the heat generation within the fiber laser is effectively controlled, thereby increasing the transverse mode instability (TMI) threshold. Additionally, the use of a long-tapered fiber enlarges the mode area and suppresses stimulated Raman scattering (SRS) effects that typically arise from increased fiber length. As a result, an output of 6030 W is achieved with an optical-to-optical (O–O) efficiency of 83.7%, a SRS suppression ratio exceeding 50 dB, and no occurrence of dynamic TMI. This approach provides a valuable reference for optimizing long-wavelength pumping to suppress nonlinear effects and also holds potential for wide-temperature operational applications.

Photoionization of neutral chlorine atom is investigated in this paper in the framework of the screening constant per unit nuclear charge (SCUNC) method. Resonance energies, quantum defects and effective charges of the 3s23p4 (3P2,1,0)ns and 3s23p4 (3P1,0)nd Rydberg series originating from both the 2P03/2 ground state and the 2P01/2 excited state of chlorine atom are reported. The present study believed to be the first theoretical investigation is compared with the recent experimental measurements (Yang et al., Astrophys. J. 810:132, 2015). Good agreements are obtained between theory and experiments. New SCUNC data are tabulated as useful references for interpreting astrophysical spectra from neutral atomic chlorine. [ABSTRACT FROM AUTHOR]

Resonance energies and quantum defects are reported for several Rydberg series for K2+ and Br3+. For K III ions, the [3s23p4 (1D2)]nd (2P,2D) and [3s3p5 (3P°2,0,1)]np, [3s23p4 (1S0)]nd (2D5/2,3/2) Rydberg series originating from the 3s23p5 (2P°1/2) metastable and 3s23p5 (2P°3/2) ground states are considered. For Br IV ions, the study is focused on the 4s24p (1D2, 3P2, 3P1)nd series originating from the 4s24p2 (1D2,3P2,3P1) states along with the 4s4p2 (3P1)np and 4s4p2 (1D2)np states originating from the 4s24p2 (3P1, 1D2) states. Calculations are performed in the framework of the modified atomic orbital theory (MAOT). Precise data are tabulated up to high excited stated n = 40. The results presented in this paper are in excellent agreement with the synchrotron radiation measurements of Alna'Washi et al. (Phys Rev A 90:023417, 2014) on K2+ and of Macaluso et al. (J Phys B At Mol Opt Phys 52:145002, 2019) on Br3+. These excellent agreements between theory and experiments indicate that the MAOT formalism can be used to report accurate high-lying excited Rydberg series of atomic species for the diagnostic and the modeling of astrophysical or laboratory plasmas. [ABSTRACT FROM AUTHOR]

The Rydberg Series and Radiative transitions in Beryllium ions have been investigated using the single-electron approximation i.e. Weakest bound electron potential model theory (WBEPMT) and quantum defect theory. The Martin expression was applied to evaluate energies and quantum defects of Rydberg levels of Be III up to n = 50. The lifetime of 157 levels have been calculated using transition probabilities of the radiative transitions. The necessary data was taken from NIST database. The radii of Rydberg levels have also been calculated. [ABSTRACT FROM AUTHOR]

Photoionization of neutral chlorine atom is investigated in this paper in the framework of the screening constant per unit nuclear charge (SCUNC) method. Resonance energies, quantum defects and effective charges of the 3s23p4 (3P2,1,0)ns and 3s23p4 (3P1,0)nd Rydberg series originating from both the 2P03/2 ground state and the 2P01/2 excited state of chlorine atom are reported. The present study believed to be the first theoretical investigation is compared with the recent experimental measurements (Yang et al., Astrophys. J. 810:132, 2015). Good agreements are obtained between theory and experiments. New SCUNC data are tabulated as useful references for interpreting astrophysical spectra from neutral atomic chlorine.

The phosphosilicate fiber-based Raman fiber laser (RFL) has great potential in achieving low-quantum defect (QD) high-power laser output. However, the laser's performance could be seriously degraded by the Raman-assisted four-wave mixing (FWM) effect and spontaneous Raman generation at 14.7 THz. To find possible ways to suppress the Raman-assisted FWM effect and spontaneous Raman generation, here, we propose a revised power-balanced model to simulate the nonlinear process in the low-QD RFL. The power evolution characteristics in this low-QD RFL with different pump directions are calculated. The simulation results show that, compared to the forward-pumped low-QD RFL, the threshold powers of spontaneous Raman generation in the backward-pumped RFL are increased by 40% and the Raman-assisted FWM effect is well suppressed. Based on the simulation work, we change the pump direction of a forward-pumped low-QD RFL into backward pumping. As a result, the maximum signal power is increased by 20% and the corresponding spectral purity is increased to 99.8%. This work offers a way for nonlinear effects controlling in low-QD RFL, which is essential in its further performance scaling. [ABSTRACT FROM AUTHOR]

We report the measurement of the quantum defects of 85Rb P3/2 and F7/2-series Rydberg levels in a room temperature vapor cell by microwave-assisted electromagnetically induced transparency (EIT) spectroscopy. First, a novel microwave optical three-photon excitation method is employed to obtain the microwave-assisted EIT spectroscopy of the 5S1/2 − 5P3/2 – nD5/2 – (n+1)P3/2 or (n-1)F7/2 transition. Next, the Stark shifts of the corresponding Rydberg states relative to the Rabi frequency of microwave field are measured with high accuracy. Finally, the quantum defects, δ0 = 2.64142(15), δ2 = 0.295 for P3/2-series, and δ0 = 0.016411(16), δ2 = -0.0784 for F7/2-series, are forcibly extracted by the modified Rydberg-Ritz formula. This result can serve as a check on advanced theoretical calculations and promote the application of quantum simulations and quantum sensors in atomic ensembles.

Common fractions N1/N2, where N1 and N2 are small integers, are quite often used for a quantum-mechanical description of microcosm objects (for example, fractional charges of quarks and some quantum characteristics, such as particle spins). Recently the fractional quantum Hall effect has been discovered, and the common fractions considerably expand their presence in microcosm physics. The theory of the fractional quantum Hall effect has appeared nontrivial, so the Nobel Prize in physics was awarded in 1998 not only for the discovery of the effect itself by Daniel Tsui and Horst Störmer in 1982, but also for the theory developed by Robert Laughlin in 1983. And now one more sensational discovery has been made: common fractions have been detected during an analysis of experimental characteristics of hydrogen-like atoms and ions (with only one electron on the outer shell). It has appeared that the effective main quantum number of the outer shell electron subject to quantum defect (the Rydberg correction) can be expressed in common fractions N1/N2. [ABSTRACT FROM AUTHOR]

The quest for qubit operation at room temperature is accelerating the field of quantum information science and technology. Solid state quantum defects with spin-optical properties are promising spin- and photonic qubit candidates for room temperature operations. In this regard, a single boron vacancy within hexagonal boron nitride (h-BN) lattice such as V B - defect has coherent quantum interfaces for spin and photonic qubits owing to the large band gap of h-BN (6 eV) that can shield a computational subspace from environmental noise. However, for a V B - defect in h-BN to be a potential quantum simulator, the design and characterization of the Hamiltonian involving mutual interactions of the defect and other degrees of freedom are needed to fully understand the effect of defects on the computational subspace. Here, we studied the key coupling tensors such as zero-field splitting, Zeeman effect, and hyperfine splitting in order to build the Hamiltonian of the V B - defect. These eigenstates are spin triplet states that form a computational subspace. To study the phonon-assisted single photon emission in the V B - defect, the Hamiltonian is characterized by electron-phonon interaction with Jahn-Teller distortions. A theoretical demonstration of how the V B - Hamiltonian is utilized to relate these quantum properties to spin- and photonic-quantum information processing. For selecting promising host 2D materials for spin and photonic qubits, we present a data-mining perspective based on the proposed Hamiltonian engineering of the V B - defect in which h-BN is one of four materials chosen to be room temperature qubit candidates.

Ab initio calculations of the adiabatic potential curves and matrix elements of radial nonadiabatic coupling of the N2 molecule for the states related to dissociation limits I-V were performed. The most important spectral characteristics of the adiabatic states agreed well with the available experimental and theoretical data. The diabatic states were constructed. The diabatic quantum defects and radial matrix elements of the configuration interaction of the dissociative and Rydberg configurations whose states converge to the ground state X2Σg+ and the first electronically excited state A2Πu of the N2+ ion were calculated. The possibility of using the results for calculating the cross sections and rate constants of dissociative recombination and associative ionization within the framework of the multichannel quantum defect theory was discussed. [ABSTRACT FROM AUTHOR]

A low quantum defect is the fundamental key to a high efficiency of any laser. To study the anticipated performance boost for a 980 nm-diode pumped cryogenically cooled Yb:CaF 2 disk laser we compared its operation at output wavelengths of 991 nm, 996 nm, and 1032 nm. Despite the higher quantum defect a maximum efficiency of 74% (output versus incident power) with an output power of 15.8 W was achieved at the 1032 nm output wavelength. This observation led to a detailed analysis of remaining loss mechanisms we are reporting on in this paper. [ABSTRACT FROM AUTHOR]