arXiv subjects

J. -P. R. Wells

Publications and source records attributed to J. -P. R. Wells.

6 recordsLinked to original sources

arXiv2024

Spectroscopy, Crystal-Field, and Transition Intensity Analyses of the C$_{\rm 3v}$(O$^{2-}$) Centre in Er$^{3+}$ Doped CaF$_{2}$ Crystals

Erbium ions in crystals show considerable promise for the technologies that will form the backbone of future networked quantum information technology. Despite advances in leveraging erbium's fibre-compatible infrared transition for classical and quantum applications, the transitions are, in general, not well understood. We present detailed absorption and laser site-selective spectroscopy of the C$_{\rm 3v}$(O$^{2-}$) centre in CaF$_2$:Er$^{3+}$ as an interesting erbium site case study. The $^{4}$I$_{15/2}$Z$_1 \rightarrow {^{4}}$I$_{13/2}$Y$_1$ transition has a low-temperature inhomogeneous linewidth of 1 GHz with hyperfine structure observable from the $^{167}$Er isotope. A parametrized crystal-field Hamiltonian is fitted to 34 energy levels and the two ground state magnetic splitting factors. The wavefunctions are used to perform a transition intensity analysis and electric-dipole parameters are fitted to absorption oscillator strengths. Simulated spectra for the $^{4}$I$_{11/2}\rightarrow {^{4}}$I$_{15/2}$ and $^{4}$I$_{13/2} \rightarrow {^{4}}$I$_{15/2}$ inter-multiplet transitions are in excellent agreement with the experimentally measured spectra. The $^{4}$I$_{13/2}$ excited state lifetime is 25.0\,ms and the intensity calculation is in excellent agreement with this value.

cond-mat.mtrl-sci↗

arXiv2022

Reproduction of the electronic and magnetic structure of the low symmetry sites of Y$_{2}$SiO$_{5}$ doped with Sm$^{3+}$ via a parameterized crystal-field model

Parametrized crystal-field analyses are presented for both the six and seven fold coordinated, C$_{1}$ symmetry Sm$^{3+}$ centers in Y$_{2}$SiO$_{5}$, based on extensive spectroscopic data spanning the infrared to optical regions. Laser site-selective excitation and fluorescence spectroscopy as well as Zeeman absorption spectroscopy performed along multiple crystallographic directions has been utilised, in addition to previously determined $g$ tensors for the $^{6}$H$_{5/2}$Z$_{1}$ and $^{4}$G$_{5/2}$A$_{1}$ states. The resultant analyses give good approximation to the experimental energy levels and magnetic splittings, yielding crystal-field parameters consistent with the few other lanthanide ions for which such analyses are available.

cond-mat.mtrl-sci↗

arXiv2022

Prediction of the Optical Polarization and High Field Hyperfine Structure Via a Parametrized Crystal-Field Model for the Low Symmetry Centers in Er$^{3+}$ Doped Y$_{2}$SiO$_{5}$

We report on the development and application of a parametrized crystal-field model for both C$_{1}$ symmetry centers in trivalent erbium-doped Y$_{2}$SiO$_{5}$. High resolution Zeeman and temperature dependent absorption spectroscopy was performed to acquire the necessary experimental data. The obtained data, in addition to the ground ($^{4}$I$_{15/2}$Z$_{1}$) state and exited ($^{4}$I$_{13/2}$Y$_{1}$) state Zeeman and hyperfine structure, was simultaneously fitted in order to refine an existing crystal-field interpretation of the Er$^{3+}$:Y$_{2}$SiO$_{5}$ system. We demonstrate that it is possible to account for the electronic, magnetic and hyperfine structure of the full 4f$^{11}$ configuration of Er$^{3+}$:Y$_{2}$SiO$_{5}$ and further, that it is possible to predict both optical polarization behavior and high magnetic field hyperfine structure of transitions in the 1.5 $μ$m telecommunications band.

cond-mat.mtrl-sci↗

arXiv2021

A Raman heterodyne determination of the magnetic anisotropy for the ground and optically excited states of Y$_{2}$SiO$_{5}$ doped with Sm$^{3+}$

We present the full magnetic g tensors of the $^{6}$H$_{5/2}$Z$_{1}$ and $^{4}$G$_{5/2}$A$_{1}$ electronic states for both crystallographic sites in Sm$^{3+}$:Y$_{2}$SiO$_{5}$, deduced through the use of Raman heterodyne spectroscopy performed along 9 different crystallographic directions. The maximum principle g values were determined to be 0.447 (site 1) and 0.523 (site 2) for the ground state and 2.490 (site 1) and 3.319 (site 2) for the excited state. The determination of these g tensors provide essential spin Hamiltonian parameters that can be utilized in future magnetic and hyperfine studies of Sm$^{3+}$:Y$_{2}$SiO$_{5}$, with applications in quantum information storage and communication devices.

cond-mat.mtrl-sci↗

arXiv2014

Resolution of Discrete Excited States in InGaN Multiple Quantum Wells using Degenerate Four Wave Mixing

We report on two pulse, degenerate four wave mixing (DFWM) measurements on shallow InGaN/GaN multi-quantum wells (MQWs) grown on sapphire substrates. These reveal pulse length limited signal decays. We have found a 10:1 resonant enhancement of the DFWM signal at the excitonic transition frequencies which thereby give a sharp discrimination of the discrete excitonic contributions within the featureless distribution seen in absorption spectra. The exciton resonances have peak positions, which yield good overall agreement with a full k.P model calculation for the quantum well energy levels and optical transition matrix elements. InGaN/GaN MQWs generally exhibit strongly inhomogeneously broadened excitation spectra due to indium fluctuation effects; this approach therefore affords a practical method to extract information on the excited excitonic states not available previously

physics.optics↗

arXiv2013

Effective-Hamiltonian parameters for \emph{ab initio} energy-level calculations of SrCl$_{2}$:Yb$^{2+}$ and CsCaBr$_{3}$:Yb$^{2+}$

Calculated energy levels from recent \emph{ab initio} studies of the electronic structure of SrCl$_{2}$:Yb$^{2+}$ and CsCaBr$_{3}$:Yb$^{2+}$ are fitted with a semi-empirical "crystal-field" Hamiltonian, which acts within the model space $4f^{14} + 4f^{13}5d + 4f^{13}6s$. Parameters are obtained for the minima of the potential-energy curves for each energy level and also for a range of anion-cation separations. The parameters are compared with published results parameters fitted to experimental data and to atomic calculations. The states with significant $4f^{13}6s$ character give a good approximation of the impurity-trapped exciton states that appear in the \emph{ab initio} calculations.

cond-mat.mtrl-sci↗