Stark Splitting Research Articles

Systematical investigations on the influence of Stark splitting of Er3+ on the potential wavelength-tunable of laser and optical amplification in several glasses

Er3+-doped glasses and fibers with broadband near infrared (NIR) emission have been widely applied in EDFA. Limited by optical gain band of Er3+-doped glasses and fibers, it was hardly meet to the demands of broadband amplification in the C + L band. In this work, six glass matrixes were employed for discussing the influence of glass matrix on the Stark splitting of Er3+ and the wavelength of laser output and amplification. The larger scalar crystal-field parameter NJ induce larger Stark splitting of Er3+-doped tellurite, germanate, and fluorophosphate glasses, which resulted in larger Δλeff. The Stark splitting of Er3+-doped tellurite, germanate, silicate, and phosphate glasses was mainly derived from homogeneous broadening, which be favor to obtain longer wavelength amplification and laser output. While that of Er3+-doped fluorophosphate and aluminate glasses was mainly derived from the inhomogeneous broadening, the amplification and laser output of Er3+ tend to operate in the shorter wavelength.

Anomalous Polarons in Two-Dimensional Organometallic Perovskite Ferroelectric.

The concept of ferroelectric polarons is proposed to partially explain the exceptional optoelectronic properties observed in lead halide perovskites (LHPs). It is intriguing but unclear how this proposal, which involves local or transient polarizations, applies in general to 2D LHPs with long-range ferroelectricity. Here, this work presents a pioneering time-domain experimental investigation of polarons in ferroelectric (IA)2(MA)2Pb3Br10 (IMPB; IA is isoamylammonium and MA is methylammonium) using transient absorption spectroscopy. Compared to non-ferroelectric LHPs, IMPB exhibits several distinct polaronic properties closely associated with macroscopic polarizations of ferroelectricity, including a prolonged polaron formation time (≈1.1ps), a Stark splitting of the bleaching (≈63 meV), and a giant polaron Mott density (≈7.6 × 1018 cm-3). These findings broaden the realm of 2D polaron systems and reveal the decisive role of static/unidirectional polarizations on polaron physics in 2D LHPs.

Polarized Upconversion of sub-100 nm Single Nanoparticles.

Upconversion nanoparticles are popular as imaging probes due to their advantages in photostability and controllable emission dimensions. However, upconversion polarization remains largely uncharted with previous reports limited to microstructures. In this work, we report the observation of polarized upconversion emissions from β-NaYF4 single nanostructures below 100 nm. At the sub-100 nm scale, nanorods, nanodiscs, and nanoplates exhibit distinctive polarization degrees despite the same doping concentrations of lanthanides. We find this varied polarization degree results from the crystallographic orientation of nanostructure in relation to the light field and can be linked to the distinctive emission spectrum profile with varied Stark splitting transition ratios from Er3+. Our findings provide a comprehensive understanding of the polarization properties of upconversion nanoparticles, revealing a previously unexplored aspect of light emission. This discovery expands our knowledge of upconversion nanoparticles and also opens new possibilities for their use in future imaging and sensing applications, where polarization sensitivity is crucial.

Exploring single rare earth doped nanophosphor for efficient white emission through codoping of Na+ and Bi3+ ions into Dy3+ activated LaPO4

Using the simple hydrothermal technique, high-purity nanocrystalline Na+ and Bi3+ co-doped Dy3+ activated LaPO4 was effectively prepared. The structural characterisation of the prepared samples was carried out using XRD, EDS, SEM and FTIR analysis. The existence of Na+, Dy3+, La3+, P5+, O2– and Bi3+ was demonstrated using EDS analysis. The direct band gap value of 4.72 eV is obtained from UV visible absorption spectrum and infer that the doped samples are suitable for optical applications. The photoluminescence excitation spectrum monitored at 474 nm and 570 nm emission, the Na+ and Bi3+ co-doped Dy3+ activated LaPO4 exhibit narrow, and intense characteristics f-f peak of Dy3+ ion at 349 nm, 363 nm, 386 nm and 452 nm. Photoluminescence emission spectrum, monitored under 349 nm, 363 nm and 386 nm shows high intense sharp blue emission peaks of Dy3+ with stark splitting at 475 nm, 478 nm, and 486 nm, yellow emission at 571 nm and 580 nm and a very feeble peak at 658 nm in the red region. When the sample is excited at 452 nm only a yellow band is present. Since the intensity of blue and yellow emission in this host matrix is so high and nearly equal, it is appropriate for cool white emission under 350 nm, 363 nm and 386 nm (near UV) excitation and under 452 nm (blue LED) excitation the prepared phosphor may emerge as highly efficient warm white light emitter suitable for general solid-state lighting applications, which can be further confirmed by CIE chromaticity analysis of the prepared sample. In photoluminescence excitation and emission spectra intensities of peaks of the samples with Bi3+ are more intense, this confirms the positive impact of co-doping of Bi3+ into the sample. The Q value from the Dexter’s formula is calculated as an average of 6.4 and is very close to 6 indicates that the interaction is dipole − dipole, which causes the non-radiative energy migration among the Dy3+ ions in the sample. The lifetime of characteristic yellow emission of Dy3+ in the Na+ and Bi3+ co-doped Dy3+ activated LaPO4 host matrix monitored under 350 nm is calculated as 0.642 ms from decay analysis, fitted by a bi-exponential function. The results support the idea that co-doping of Bi3+ and Na+ into the LaPO4:Dy3+ matrix could emerge as a potential white light emitting phosphor for phosphor-converted white LED application.

Designing ITER motional Stark effect line shift (MSE-LS) spectrometers.

As a part of ITER beam aided diagnostics, the design of Motional Stark Effect (MSE) diagnostic observing the emission from the Balmer-α line is underway. The physics of Stark splitting shows that the Stark manifold is polarization dependent, and the energy splitting results in a line shift proportional to the electric field. Due to the challenges of maintaining the calibration of the plasma facing mirrors in ITER, the conventional MSE polarimetry measurement technique is replaced with a spectral approach that is deemed more favorable in the ITER environment. The MSE line shift (LS) diagnostic is designed to quantify the Lorentz electric field magnitude by measuring the Stark manifold using visible spectroscopy. In the presence of large magnetic fields and high energy heating beams of 1MeV, the expected Stark splitting is much larger than in typical devices. The MSE-LS design has unique challenges requiring careful consideration and modeling of its viewing geometry and photon budget. The MSE-LS approach on ITER is promising but has stringent demands on the allowable errors for the statistical and systematic fitting uncertainties. In this study, a full system model and numerical simulations of data for each sightline are completed. For a range of optical transmission fractions, photon noise analysis is conducted to determine the statistical uncertainties. This provides guidance on the spectrometer throughput, dispersion at the detector, optics, and other design choices. A conceptual design of a high throughput spectrometer with a volume phase transmission grating is presented.

Crystal field effects of Al doping on the Stark splitting and gain bandwidth of erbium doped silica fibers

In this study, erbium-doped silica fibers (EDFs) with different Al/Er ratios were prepared by high-temperature source combined with the modified chemical vapor deposition (MCVD) method. The effects of different Al/Er ratios on the gain performance of erbium-doped silica fiber amplifiers (EDFA) were investigated. The EDFA demonstrated in this paper achieves a maximum gain of 45 dB at 1560 nm when the signal power is −20 dB, while the bandwidth of 20 dB gain is up to 68 nm (1532∼1600 nm). Additionally, the effect of Al doping on the crystal field around the Er ion was analyzed and the Stark energy level distribution of the Er ions was further derived. Our approach offers a feasible solution for C + L band amplification from the perspective of Stark effect and crystal field analysis.

Dressing Stark splitting of time-resolved excitation spectra in Eu3+-doped BiPO4 micro-crystals

The Stark splitting of 5DJ-7FJ transitions has been investigated by time-resolved dressing excitation spectra in Eu3+-doped BiPO4 micro-crystals with different phase structures. The evolution of the Stark transition peaks significantly depends on the laser power, bandwidth, delay time, temperature, and phase structures of BiPO4 crystals. It is explained by photon-phonon coupling dressing effect. There is competition between the crystal field splitting and the dressing splitting alignment in the line-shape evolution. The time-resolved dressing excitation spectrum provides an effective method to investigate Stark splitting and modulate line-shape for applications in optical communication.

The spectrally resolved photoluminescence decay in YAG:Er, ZnO and SiO2 crystals

We present an optical setup for measuring spectrally resolved photoluminescence (PL) mean decay time using conventional UV LED with sinusoidal excitation and a phase shift method. The phase sensitive detection was applied on the Er-doped yttrium aluminium garnet single crystal (YAG:Er, grown by the micro-pulling-down method) and hydrothermally grown zinc oxide micro-crystallites (ZnO). Commercial ZnO and silicon oxide (SiO2) microcrystalline powders were measured for comparison. SiO2 powder was annealed in O2 plasma at 500 °C for cleaning. While YAG:Er shows well resolved greenish PL peaks with mean decay time about 15 μs related to the Stark splitting of Er3+ (4f11) states and ZnO micro-powder broad reddish PL with similar PL decay time, the plasma treated SiO2 powder shows weak bluish defect-related PL with significantly faster mean decay times below 100 ns.

Sensitivity of radio-frequency electric field sensor based on Rydberg Stark effect

Rydberg atoms hold special attraction in electric applications due to their large transition electric dipole moments and huge polarization, which leads to a strong response of atom to electric fields. In radio-frequency (RF) fields, the Rydberg levels are AC Stark shift and splitting, which can realize the study of high-sensitivity electric field sensor of Rydberg atoms. In this work, we use the simpler Shirley’s time-independent Floquet Hamiltonian model to calculate the AC Stark energy spectrum of Cs Rydberg atoms. This model can reduce the basic Hamiltonian into such a Hamiltonian that includes only those Rydberg states that have direct dipole-allowed transitions with the target state, thereby significantly improving the speed of computation. The accuracy of the calculation is proved by fitting with the calculated frequency shift of DC Stark energy levels in the weak fields, and the polarizability of 60D<sub>5/2</sub> and 70D<sub>5/2</sub> Rydberg atomic states are obtained by fitting with the measured ion spectra of DC Stark Cs ultra-cold Rydberg atoms in magneto-optical trap. In addition, we calculate the AC Stark shift of Cs Rydberg atom <inline-formula><tex-math id="M2">\begin{document}$ \left| {60{{\text{D}}_{5/2}},{m_j} = 1/2} \right\rangle $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240162_M2.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240162_M2.png"/></alternatives></inline-formula> state in electric fields with different frequencies with <i>ε</i> = 100 mV/m. Rydberg atoms provide a structured spectrum of sensitivity to electric fields due to strong resonant interaction and off-resonant interaction with many dipole-allowed transitions to nearby Rydberg states. This kind of the frequency response structure is of significance to a broadband sensor. And we calculate the sensitivity and the scaling of the signal-to-noise ratio (SNR), <i>β</i>, varying with detuning from the <inline-formula><tex-math id="M3">\begin{document}$ \left| {60{{\text{D}}_{5/2}}} \right\rangle \to \left| {61{{\text{P}}_{3/2}}} \right\rangle $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240162_M3.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240162_M3.png"/></alternatives></inline-formula> transition. The value of <i>β</i> allows one to use the result for any Rydberg state sensor to determine the SNR for any <i>Ε</i> in a 1 s measurement. Therefrom, Rydberg sensor can preferentially detect many RF frequencies spreading across its carrier spectral range without modification while effectively rejecting large portions where the atom response is significantly weaker, and the signal depends primarily on the detuning of the RF field to the nearest resonance which does not convey the RF frequency directly.

The impact of pair Er3+/Yb3+ on titanate-germanate glasses: Physicochemical and near-infrared luminescence investigations

This work combines photoluminescence methods, Raman spectroscopy, and X-ray diffraction (XRD) to expand the knowledge of the effects of pair rare earth ions doping on the physicochemical and near-IR properties of glasses. For this purpose, glass systems based on GeO2-BaO-Ga2O3 (GBG) and TiO2-GeO2-BaO-Ga2O3 (TGBG) doped with Er3+ ions (0.1, 0.25, 0.5 mol%) and Yb3+ ions (0.5, 1.25, 2.5 mol%) were synthesized and analyzed. The near-IR luminescence band corresponding to Er3+:4I13/2 → 4I15/2 is narrowed for germanate-based glasses (FWHM = 31 nm), whereas in the presence of TiO2 is more intense and broadened (FWHM = 65 nm). The energy transfer efficiencies between Yb3+ and Er3+ ions in glass samples have been calculated. Notably, the absorption spectra showed the Stark splitting for the band due to the 4I15/2 → 2H11/2 hypersensitive transition. Finally, we find the formation of Er2Ti2O7 and Yb2Ti2O7 crystalline phases in highly doping titanate-germanate samples. The results provide valuable ideas to evaluate the effect of the rare earths doping procedure on properties of designed glasses for near-IR luminescence applications.

Stark splitting of intense red emission for Er3+ in Oh symmetry sites realizing optical temperature sensing in biological applications

Stark splitting of intense red emission for Er3+ in Oh symmetry sites realizing optical temperature sensing in biological applications

Effect of alkali and alkaline earth metal ion as glass modifiers on the spectroscopic characteristics of Er3+‐ion doped lead silicate glasses

AbstractThe spectroscopic characteristics of Er‐doped lead silicate glasses were investigated with respect to the effects of glass modifiers (Li+, Na+, K+, Mg2+, Ca2+, Sr2+, and Ba2+) with various optical basicities. Using the absorption spectra of the glasses, the Judd–Ofelt parameters of the glasses were calculated and examined, with an emphasis on the glass emission intensity ratio at 1572 nm. The spectra of the samples at low temperatures were examined, and the Stark splitting of Er3+ was investigated. The McCumber method was used to determine the emission cross sections of glasses. The SPM glass exhibited high values of full width at half maximum (51.24 nm) and the emission cross section at 1572 nm (1.908 × 10−21 cm2), with potential applications for guiding component design of 1.5‐μm fiber lasers and amplifiers.

Ultraviolet interlayer excitons in bilayer WSe2.

Interlayer excitons in van der Waals heterostructures are fascinating for applications like exciton condensation, excitonic devices and moiré-induced quantum emitters. The study of these charge-transfer states has almost exclusively focused on band edges, limiting the spectral region to the near-infrared regime. Here we explore the above-gap analogues of interlayer excitons in bilayer WSe2 and identify both neutral and charged species emitting in the ultraviolet. Even though the transitions occur far above the band edge, the states remain metastable, exhibiting linewidths as narrow as 1.8 meV. These interlayer high-lying excitations have switchable dipole orientations and hence show prominent Stark splitting. The positive and negative interlayer high-lying trions exhibit significant binding energies of 20-30 meV, allowing for a broad tunability of transitions via electric fields and electrostatic doping. The Stark splitting of these trions serves as a highly accurate, built-in sensor for measuring interlayer electric field strengths, which are exceedingly difficult to quantify otherwise. Such excitonic complexes are further sensitive to the interlayer twist angle and offer opportunities to explore emergent moiré physics under electrical control. Our findings more than double the accessible energy range for applications based on interlayer excitons.

Tuning phase and photoluminescent properties of ZrO2:Eu3+ coatings formed by plasma electrolytic oxidation and Judd-Ofelt analysis of composite materials

Eu3+ doped Zirconia coatings were synthesized by the electrochemical plasma electrolytic oxidation method in only 8 min from the pure zirconium substrate. The phase constitution from pure monoclinic to pure tetragonal and exactly in between was achieved by using different concentrations of Na3PO4 and NaAlO2 electrolytes. The complex emission spectra composed of Eu2+, Eu3+, and ZrO2 defect emission greatly depend on the excitation wavelength and phase constitution. Eu3+ photoluminescence properties depend on the phase, which is reflected by the different Stark splitting and different intensities of transitions. Thus, both phase and photoluminescent properties of ZrO2 coatings are fine-tuneable. Judd-Ofelt analysis was performed from the emission and excitation spectra, showing that all 3 intensity parameters depend linearly on the phase constitution, being largest in the pure monoclinic phase. The mixed phase has Judd-Ofelt parameters between those in pure phases. Eu3+ has 2.45 times more preference to get incorporated into the tetragonal than in the monoclinic phase in the mixed phase samples. The general equation for Judd-Ofelt parameters in a compound with mixed constituents and probability of incorporation is introduced, allowing also for a prediction of the spectrum shape based on the Judd-Ofelt parameters of pure-phase compounds. Python software code for estimating the percent of incorporation by multiple linear regression model is also provided.

Ratiometric luminescent thermometry for the third bioimaging window by Er3+ doped garnet with large Stark splitting

Based on the 4I13/2 → 4I15/2 emission (1450–1700 nm) of Er3+ in garnet, which is matching well with third bioimaging window (NIR-III), we propose a ratiometric near-infrared (NIR) thermometer (YAGG:Ce-Er) in NIR-III by utilizing thermal coupling between Stark levels of 4I13/2, where energy levels were split into seven sublevels (I–VII). The energy gaps between Stark sublevel VII and I (ΔEVII-I) and V and I (ΔEV-I) of the 4I13/2 level, calculated from the temperature dependence of intensity ratios of the two selected thermal couples, corresponded well with the theoretical values. This agreement supports the analysis that the system can be utilized as a Boltzmann thermometry. Moreover, the relative sensitivity (Sr) within the temperature range commonly encountered in organisms (25–60 °C) reached a value of 0.63 ± 0.03% K−1 for the VII/I ratio and 0.57 ± 0.07% K−1 for the V/I ratio. These high relative sensitivity values indicate the strong potential for practical application in various biological fields.

Coherent ultrafast photoemission from a single quantized state of a one-dimensional emitter.

Femtosecond laser-driven photoemission source provides an unprecedented femtosecond-resolved electron probe not only for atomic-scale ultrafast characterization but also for free-electron radiation sources. However, for conventional metallic electron source, intense lasers may induce a considerable broadening of emitting energy level, which results in large energy spread (>600 milli-electron volts) and thus limits the spatiotemporal resolution of electron probe. Here, we demonstrate the coherent ultrafast photoemission from a single quantized energy level of a carbon nanotube. Its one-dimensional body can provide a sharp quantized electronic excited state, while its zero-dimensional tip can provide a quantized energy level act as a narrow photoemission channel. Coherent resonant tunneling electron emission is evidenced by a negative differential resistance effect and a field-driven Stark splitting effect. The estimated energy spread is ~57 milli-electron volts, which suggests that the proposed carbon nanotube electron source may promote electron probe simultaneously with subangstrom spatial resolution and femtosecond temporal resolution.

Crystal structure and luminescence dynamics of highly pure LiM(PO3)3:Eu3+ (M = Sr, Ca) red phosphors for white light emitting diodes

Highly pure red phosphors LiM(PO3)3:Eu3+ (M = Sr, Ca) doped with Eu3+ (1 mol%) were synthesized via solution combustion method and their crystal structure and luminescence dynamics were studied to explore its suitability in white light emitting diodes. The Rietveld refinement analysis of the powder X-ray diffraction patterns reveals that the phosphors belong to the pure triclinic phase of LiSr(PO3)3 and LiCa(PO3) with space group P-1¯ (2). The scanning electron microscopy images showed the agglomerated morphology. The photoluminescence emission spectra under 393 nm show an orange band at 594 nm and a red band at 613 nm ascribed to 5D0 → 7F1, 5D0 → 7F2 transitions of Eu3+ ion in both the phosphors. Moreover, the spectroscopic properties such as luminescence behaviour, and Stark splitting were used to examine the symmetry of Eu3+ ions in LiM(PO3)3:Eu3+ (M = Sr, Ca) phosphors in terms of distortion induced upon doping. The Stark splitting shows that the actual site symmetry for Eu3+ ion was estimated to be D2 type for both phosphors. The photometric properties of LiCa(PO3)3:Eu3+ such as Commission International de l’Eclairage coordinates (x = 0.64, y = 0.36) near to the standard one (red), high color purity (95%) and higher brightness reveal that the phosphor has the capability of acting as a red component in n-UV white light emitting diodes.

Electric field intensity measurement by using doublet electromagnetically induced transparency of cold Rb Rydberg atoms

We demonstrate a simple method to measure electric field intensity by using doublet electromagnetically induced transparency (EIT) spectra of cold Rb Rydberg atoms, where the frequency of the coupling laser does not need to be locked. Based on the Stark splitting of the Rb Rydberg state, 10D3/2, under electric fields and the corresponding calculated polarizabilities, the real electric field intensity is calculated using the difference in radio-frequency diffraction between two acousto-optic modulators, which acts as a frequency criterion that allows us to measure the electrical field without locking the coupling laser. The value measured by this simple method shows a good agreement with our previous work [Opt. Express 29 1558 (2021)] where the frequency of the coupling laser needs to be locked with an additional EIT spectrum based on atom vapor and a proportional–integral–differential feedback circuit. Our presented method can also be extended to the measurement of electric field based on hot Rydberg atom vapor, which has application in industry.

Super low-frequency electric field measurement based on Rydberg atoms.

We demonstrate the measurement of super low-frequency electric field using Rydberg atoms in an atomic vapor cell with inside parallel electrodes, thus overcoming the low-frequency electric-field-screening effect at frequencies below a few kHz. Rydberg electromagnetically induced transparency (EIT) spectra involving 52D5/2 state is employed to measure the signal electric field. An auxiliary DC field is applied to improve the sensitivity. A DC Stark map is demonstrated, where the utilized 52D5/2 exhibits mj = 1/2, 3/2, 5/2 Stark shifts and splittings. The mj = 1/2 state is employed to detect the signal field because of its larger polarizability than that of mj = 3/2, 5/2. Also, we show that the strength of the spectrum is dependent on the angle between the laser polarizations and the electric field. With optimization of the applied DC field to shift the mj = 1/2 Rydberg energy level to a high sensitivity region and the laser polarizations to obtain the maximum mj = 1/2 signal, we achieve the detection of the signal electric field with a frequency of 100 Hz down to 214.8 µV/cm with a sensitivity of 67.9 µV cm-1Hz-1/2, and the linear dynamic range is over 37 dB. Our work extends the measurement frequency of Rydberg sensors to super low frequency with high sensitivity, which has the advantages of high sensitivity and miniaturization for receiving super low frequency.

Near-infrared luminescence enhancement in Yb3+/Ho3+ co-doped bismuth-tellurite glass by tailoring glass network

In this work, the glass network has been tailored by introducing the modifier WO3 when a Ho3+/Yb3+ co-doped bismuth-tellurite glass composition was designed. The physical, absorption, emission, structure, and gain characteristics of the glasses with the different contents of WO3 were investigated comprehensively based on various tests and analytical methods such as absorption spectra, fluorescence spectra, Raman spectra, and J-O theory. The results show that both the optical band gap and the bridge oxygen content are enhanced remarkably while the substitution of TeO2 by WO3, accelerating the transition from [TeO3] to [TeO4] units. Simultaneously, the value of Ω6 reached the maximum of 2.26×10-20 cm2 when the WO3 is equal to 10 mol%, indicating that the Stark splitting of Ho3+: 5I7 energy level is the weakest. The optimal FWHM and the gain coefficient are 143.3 nm and 2.22 cm-1, respectively. Furthermore, a blue shift of the central wavelength in absorption and emission peaks can be observed at the 2 μm band. As mentioned above, the bismuth-tellurite glass prepared is an ideal gain material that can realize a wider spectra span.