Pump Excitation Research Articles

Stokes and anti-Stokes emission characteristics of Er3+/Yb3+ co-doped zinc tellurite glasses under 377 and 1550 nm excitations for solar energy conversion application

One of the best rare earth combinations for down- and up-converting the solar photons is Er3+/Yb3+. Therefore, at present, by using the traditional melt quench technique, zinc tellurite glasses doped with Er3+ and Er3+/Yb3+ were characterised. Several methods of down-conversion that result in the emission of 1000 nm from the acceptor (Yb3+) under excitation of donor (Er3+) were studied. On the other hand, the impact of acceptor (Yb3+) concentration and excitation pump power on the excited state absorption and its influence on the up-conversion emission (1000 nm) properties were investigated in detail under 1535 nm excitation. The studies on emission and decay results are discovered to be very significant. Suggesting that these glasses when used as conversion layers, can append the conversion efficiency of Si-based solar cells.

H_3^+ absorption and emission in local (U)LIRGs with JWST NIRSpec: Evidence for high H_2 ionization rates

We study the $3.4-4.4$ fundamental rovibrational band of H$_3^+$, a key tracer of the ionization of the molecular interstellar medium (ISM), in a sample of 12 local ($d$$<$400\,Mpc) (ultra)luminous infrared galaxies ((U)LIRGs) observed with JWST NIRSpec. The P, Q, and R branches of the band are detected in 13 out of 20 analyzed regions within these (U)LIRGs, which increases the number of extragalactic H$_3^+$ detections by a factor of 6. For the first time in the ISM, the H$_3^+$ band is observed in emission; we detect this emission in three regions. In the remaining ten regions, the band is seen in absorption. The absorptions are produced toward the $3.4-4.4$ hot dust continuum rather than toward the stellar continuum, indicating that they likely originate in clouds associated with the dust continuum source. The H$_3^+$ band is undetected in Seyfert-like (U)LIRGs where the mildly obscured X-ray radiation from the active galactic nuclei might limit the abundance of this molecule. For the detections, the H$_3^+$ abundances, $N($H$_3^+$) H (0.5--5.5)times 10$^ imply relatively high ionization rates, $ H_2 $, of between 3times 10$^ $ and $>$4times 10$^ $, which is lower than the molecular outflow velocities measured using other tracers such as OH\,119 or rotational CO lines. This suggests that H$_3^+$ traces gas close to the outflow-launching sites before it has been fully accelerated. We used nonlocal thermodynamic equilibrium models to investigate the physical conditions of these clouds. In seven out of ten objects, the H$_3^+$ excitation is consistent with inelastic collisions with H$_2$ in warm translucent molecular clouds kin $sim 250--500\,K and H_2 )$sim 10$^ $). In three objects, dominant infrared pumping excitation is required to explain the absorptions from the (3,0) and (2,1) levels of H$_3^+$ detected for the first time in the ISM.

Charge self-shuttling triboelectric nanogenerator based on wind-driven pump excitation for harvesting water wave energy

The most important ocean energy sources are wind energy and water wave energy, both of which are significant to carbon neutrality. Due to uneven distribution and random movement, the conversion efficiency from the two energies into electrical energy is limited, so the coupling of them is necessary. However, the current energy harvesting technologies generally target one certain type, or are simple mechanical coupling. Here, we propose a composite water wave energy harvesting scheme with wind excitation based on triboelectric nanogenerators (TENGs). A rotation TENG driven by wind is introduced as a pump to inject charges into the main TENG. For the main TENG driven by water waves, a specially designed charge self-shuttling mode is applied (CSS-TENG). Under the pump excitation, the shuttling charge amount is increased by 11.8 times, and the peak power density reaches 33.0 W m−3, with an average power density of 2.4 W m−3. Furthermore, the CSS-TENG is expanded into an array by parallel connection, and the practical applications are demonstrated. This work organically couples the wind and water wave energy in the ocean scene, through the charge pumping and self-shuttling mode, providing a new pathway for the synergistic development of clean and renewable energy sources.

Enhancing 2.7 µm emission of Er3+ in bismuth glass by introducing ZnO

In recent years, 2.7 μm lasers have attracted the attention of many researchers due to their wide application in military, medical, aerospace and other fields. This study investigates the gain effect of ZnO on Er3+-doped bismuthate glasses by partially replacing GeO2 in the glass with ZnO. It is found that under 980 nm pump excitation, with the increase of ZnO, the emission of Er3+ at 1.5 μm and 2.7 μm was enhanced. This result is consistent with the changing trend of J-O parameter Ω2. All these results confirmed that the introduction of ZnO into bismuthate glasses is a reasonable and effective method to enhance the mid-infrared 2.7 μm emission in Er3+-doped bismuthate glasses. Therefore, the current research indicates that an appropriate amount of ZnO in Er3+-doped bismuthate glasses is a suitable materials for 2.7 um fiber lasers.

Time- and angle-resolved photoemission spectroscopy with wavelength-tunable pump and extreme ultraviolet probe enabled by twin synchronized amplifiers.

We describe a setup for time- and angle-resolved photoemission spectroscopy with wavelength-tunable excitation and an extreme ultraviolet probe. It is enabled by using the 10kHz twin Ti:sapphire amplifiers seeded by the common Ti:sapphire oscillator. The typical probe energy is 21.7eV, and the wavelength of the pump excitation is tuned between 2400 and 1200nm by using the optical parametric amplifier. The spectral width of the extreme ultraviolet probe is 53meV, and the time resolution is dependent on the wavelength for the pump, better than 60fs for the pump energy >0.7eV. This system enables the pump energy to be matched with a specific interband transition and to probe a wider energy-momentum space. We present the results for the prototypical materials of highly oriented pyrolytic graphite and Bi2Se3 to show the performance of our system.

Direct Observation of Circularly Polarized Nonlinear Optical Activities in Chiral Hybrid Lead Halides.

Circularly polarized light emission is a crucial application in imaging, sensing, and photonics. However, utilizing low-energy photons to excite materials, as opposed to high-energy light excitation, can facilitate deep-tissue imaging and sensing applications. The challenge lies in finding materials capable of directly generating circularly polarized nonlinear optical effects. In this study, we introduce a chiral hybrid lead halide (CHLH) material system, R/S-DPEDPb3Br8·H2O (DPED = 1,2-diphenylethylenediammonium), which can directly produce circularly polarized second harmonic generation (CP-SHG) through linearly polarized infrared light excitation, exhibiting a polarization efficiency as high as 37% at room temperature. To understand the spin relaxation mechanisms behind the high polarization efficiency, we utilized two models, so-called D'yakonov-Perel' (DP) and Bir-Aronov-Pikus (BAP) mechanisms. The unique zigzag inorganic frameworks within the hybrid structure are believed to reduce the dielectric confinement and exciton binding energy, thus enhancing spin polarization, especially in regions with a high excitation pump fluence based on the DP mechanism. In the case of low excitation pump fluence, the BAP mechanism dominates, as evidenced by the observed decrease in the polarization ratio from CP-SHG measurement. Using density functional theory analysis, we elucidate how the distinctive 8-coordination environment of lead bromide building blocks effectively suppresses spin-orbit coupling at the conduction band minimum. This suppression significantly diminishes spin-splitting, thereby slowing the spin relaxation rate.

Preparation of Er3+, Ho3+, Yb3+-doped Bi2WO6 upconversion luminescent materials and their temperature sensing properties

A high-temperature solid-phase method was used to prepare codoped Bi2WO6 upconversion luminescent materials with different concentrations of Er3+, Ho3+, and Yb3+. The microstructure, upconversion luminescence and temperature sensing properties of the synthesized powders were analyzed. X-ray diffraction (XRD) patterns showed that the doping of Er3+, Ho3+, and Yb3+ did not affect the orthorhombic crystal structure of the Bi2WO6 matrix material. As the calcination temperature increased from 800 °C to 1000 °C for 3h, the average particle sizes of the 1% Er3+, 1% Ho3+, 1% Yb3+: Bi2WO6 samples decreased, and the luminescence weakened. Scanning electron microscopy (SEM) images showed that the morphology of the sample for 1% Er3+, 1% Ho3+, 1% Yb3+: Bi2WO6 with calcination at 800 °C was nearly spherical, with particle sizes ranging from 1 to 5 μm and some agglomeration. SEM mapping showed that the elements were more uniformly distributed on the surfaces of the sample particles, and energy-dispersive X-ray spectroscopy (EDS) analysis showed that each element was distributed with in the particles. Er3+, Ho3+, and Yb3+ codoping was used to regulate the Yb3+ doping concentration, and under 980 nm excitation, the strongest upconversion emission was obtained for the prepared 1% Er3+, 1% Ho3+, 1% Yb3+ samples. Compared with that for the Er3+, Yb3+-doped Bi2WO6 sample, the luminescence intensity of the characteristic emission peak of Er3+ at 525 nm for the Er3+, Ho3+, Yb3+-doped sample was weakened, while the luminescence of the characteristic emission peak of Ho3+ was enhanced; these results indicated that energy transfer from Er3+ to Ho3+ occurred. The intensities of the four emission peaks at 525 nm, 546 nm, 660 nm, and 756 nm in the 1% Er3+, 1% Ho3+, 1% Yb3+-doped Bi2WO6 sample increased with increasing excitation pump power from 45 mW to 233 mW. Based on the relationship between the excitation pump power and the emission intensity, all four luminescence peaks originated from two-photon absorption. The fluorescence intensity ratio versus temperature was fitted using three different nonthermally coupled energy level pairs in the range from 298 K to 573 K. The maximum absolute temperature sensitivity of 0.296 K-1 was obtained at 573 K for the Ho3+ nonthermally coupled energy level pair, and the maximum relative temperature sensitivity of 0.279 K-1 was obtained at 298 K. The temperature resolution for characterization using the above nonthermally coupled energy level pairs was calculated, with the temperature resolution δT yielding a minimum value of 0.03 K. The CIE color coordinates at different temperatures were calculated, and the color coordinates gradually moved from the green region to the red region.

Self‐Boosting Energy Generation via Triboelectric Nanogenerator–Capacitor Coupling

AbstractWith the development of wearable and wireless electronic devices, the triboelectric nanogenerator (TENG) is attracting interest as a candidate for portable power. Many studies are conducted to increase the surface charge density of the TENG, such as external charge pumping or external electron excitation strategies. However, there are limitations in that another additional external energy source is required. Here, a TENG–capacitor (TC) coupling system that can maximize energy generation and storage efficiency within a limited volume is proposed. Density functional theory calculations indicate that the electric field induced on capacitor increases the fermi energy of positive triboelectric material, resulting in more charge transfer between two triboelectric materials. TC coupling system enhances TENG output performance and the capacitor charging rate in a virtuous cycle. This study provides new insights into TENG structural design and an important guideline for the use of TENG as a portable power source for wearable and wireless applications.

Dual-Hyperspectral Optical Pump-Probe Microscopy with Single-Nanosecond Time Resolution.

In recent years, optical pump-probe microscopy (PPM) has become a vital technique for spatiotemporally imaging electronic excitations and charge-carrier transport in metals and semiconductors. However, existing methods are limited by mechanical delay lines with a probe time window up to several nanoseconds (ns) or monochromatic pump and probe sources with restricted spectral coverage and temporal resolution, hindering their amenability in studying relatively slow processes. To bridge these gaps, we introduce a dual-hyperspectral PPM setup with a time window spanning from nanoseconds to milliseconds and single-nanosecond resolution. Our method features a wide-field probe tunable from 370 to 1000 nm and a pump spanning from 330 nm to 16 μm. We apply this PPM technique to study various two-dimensional metal-halide perovskites (2D-MHPs) as representative semiconductors by imaging their transient responses near the exciton resonances under both above-band gap electronic pump excitation and below-band gap vibrational pump excitation. The resulting spatially and temporally resolved images reveal insights into heat dissipation, film uniformity, distribution of impurity phases, and film-substrate interfaces. In addition, the single-nanosecond temporal resolution enables the imaging of in-plane strain wave propagation in 2D-MHP single crystals. Our method, which offers extensive spectral tunability and significantly improved time resolution, opens new possibilities for the imaging of charge carriers, heat, and transient phase transformation processes, particularly in materials with spatially varying composition, strain, crystalline structure, and interfaces.

Experimental investigation on the internal stress of bismuth-doped fiber and its effect on the noise figure of Bismuth-doped fiber amplifier.

The noise figure (NF) of a fiber amplifier is one of the key measures of amplification performance, which characterizes the quality of the amplified signal. Residual stresses are inevitably generated during the manufacturing process of optical fibers, and this can lead to changes in the refractive index (RI) distribution of the fiber. Further, the change in RI distribution causes the mode-field characteristics of the fiber to change as well, and this ultimately has an impact on the NF performance of the amplifier. However, until now, there have been fewer studies on the effect of residual stress on the NF of the fiber amplifiers. In this work, we took a commercial single-mode bismuth-doped fiber (BDF) as an example and used a self-developed stress test device to measure its residual stress and refractive index distribution and compare it with that of a passive fiber. We also comprehensively compared the distribution of residual stress and refractive index of the fiber at different pump powers and pump wavelengths. Finally, we performed numerical simulations of the bismuth-doped fiber amplifier (BDFA) based on the BDF under the theoretical mode field area and BDF after the expansion of the mode field area due to stresses to compare the NF performance. The results demonstrate that: the entire cross-section (core and cladding) of the BDF exhibits tensile stress (>0 MPa), where the residual stress at the core of the BDF is nearly 9.8 MPa higher than that of the passive fiber; The residual stress makes the mode-field area of the BDF expand by 26.7% compared with the theoretical values, which ultimately makes the NF of the BDFA rise from 4.6 dB to 4.7 dB; The stress at the BDF core is exacerbated by pump excitation, where it is elevated by about 26% and 5% compared to vacancy at 1240 nm and 1310 nm pumps, which is most likely attributed to thermal effects. Therefore, it is necessary to consider the effect of residual stresses in the fabrication of optical fibers to better achieve the radius of the expected indicators. This work contributes to the better development of O-band BDFAs, especially for pre-simulation of the actual performance of BDFAs with a practical reference.

Real-time dynamics of vibronic wavepackets within Rydberg and ion-pair states of molecular iodine.

Real-time dynamics of vibrationally and electronically excited I2 molecules has been investigated experimentally using the pump-probe technique. A 2-photon excitation was performed either at 269 nm or 266 nm. An electronic and vibrational wavepacket was built as coherent superposition of a few (269 nm excitation) or many (266 nm excitation) Rydberg states of the and series partly coupled with ion-pair states. The probe operated by ionisation or photodetachement. The energy and angular distribution of the resulting photoelectrons, I+ photocations and I- photoanions were monitored. During the dynamics that is turned on by the pump excitation, the wavepacket splits and explores a variety of electronic states of Rydberg and ion-pair character. The experimental results were complemented by molecular dynamics calculations. This provided invaluable information to identify wavepacket motion along ion-pair potential energy curves.

Numerical investigation on the effects of wave suppression baffles in vehicle-integrated water tanks

The danger of liquid sloshing in pump-driven water tanks has significantly increased due to the growing need to integrate a water tank into new energy vehicles. The best approach to reduce the negative effects of liquid sloshing is to add baffles to the integrated water tank. The addition of baffles to integrated water tanks to reduce liquid sloshing is investigated in this study using the discontinuous mesh approach and the coupled level set and volume of fluid (CLSVOF) method. Comparative experiments and simulations are used to confirm the reliability of the method. In this study, the length ratio, distance to initial free surface, and angle of the added baffle are taken into consideration. The free surface height, magnitude velocity, turbulence energy, and flow field are used to assess the impact of the baffle on the suppression of liquid sloshing. The addition of baffles can improve the liquid sloshing phenomenon caused by the pump excitation conditions in the integrated water tank, increase the volume suction of liquid, inhibit the height of the wave and reduce the liquid flow rate in the tank. Also, at the depth where the baffle has the most obvious suppression effect, the deeper the baffle, the lower the height of the free surface in the tank and the lower the average magnitude velocity in the tank cross-section. The baffle reduces the height of the free surface in the tank to 6.39 mm, and the magnitude of maximum average velocity in the tank cross-section is reduced to 0.12 m/s.

A coherent phonon-induced hidden quadrupolar ordered state in Ca2RuO4

Ultrafast laser excitation provides a means to transiently realize long-range ordered electronic states of matter that are hidden in thermal equilibrium. Recently, this approach has unveiled a variety of thermally inaccessible ordered states in strongly correlated materials, including charge density wave, ferroelectric, magnetic, and intertwined charge-orbital ordered states. However, more exotic hidden states exhibiting higher multipolar ordering remain elusive owing to the challenge of directly manipulating and detecting them with light. Here we demonstrate a method to induce a dynamical transition from a thermally allowed to a thermally forbidden spin-orbit entangled quadrupolar ordered state in Ca2RuO4 by coherently exciting a phonon that is strongly coupled to the order parameter. Combining probe photon energy-resolved coherent phonon spectroscopy measurements with model Hamiltonian calculations, we show that the dynamical transition is manifested through anomalies in the temperature, pump excitation fluence, and probe photon energy dependence of the strongly coupled phonon. With this procedure, we introduce a general pathway to uncover hidden multipolar ordered states and to control their re-orientation on ultrashort timescales.

Analysis of influencing factors on vibration characteristics of electro-hydraulic vibration cutting system

The cutting process of the cantilever tunneling machine mainly generates excitation through the cutting motor or the hydraulic cylinder driven by the hydraulic system. Regardless of the driving method, the frequency width of the excitation system is limited, difficult to control, and the excitation effect is poor. Therefore, in order to improve excavation efficiency, the excitation system parallel to the original cutting and rotating system is designed. Based on the excitation characteristics caused by alternating fluid flow, the core component of the excitation system, hydraulic exciter, is designed, and the dynamics and dynamic characteristics of the excitation system are analyzed. Based on AMESim software, analyze the impact of factors such as pump displacement, excitation frequency, and pipeline parameters on the operational performance of the electro-hydraulic vibration cutting system, and conduct experimental verification by building a cutting test bench. The experimental results show that as the inner diameter of the pipeline increases, the fluctuation at the acceleration turning point decreases in each cycle and approaches the peak faster. As the excitation frequency increases, the cutting acceleration of the electro-hydraulic excitation cutting system decreases first and then increases, verifying the accuracy of the simulation results. In the experiment, it was found that the acceleration transformation range of the cutting head of the excitation system is the smallest and most stable when the excitation frequency is 30 Hz. In order to verify that the excitation frequency of 30 Hz is the optimal frequency, further contact force tests were conducted on the cutting teeth. It was found that when the hydraulic excitation system adds a 30 Hz excitation frequency, the contact force on the cutting teeth is the smallest. It is more conducive to reducing the damage and wear of the cutting head, and the cutting effect of the cutting head is more obvious. The research results are beneficial for improving the cutting performance of the electro-hydraulic excitation cutting system, providing theoretical support for the selection of cutting parameters for excavation machinery and hydraulic excitation, and improving the existing theoretical system for active excitation cutting vibration analysis of excavation machines.

Recent progress on nonlinear ultrasonic phased array for closed-crack imaging

Closed cracks are challenging defects for ultrasonic testing since they are transparent to conventional ultrasound techniques. This can cause the underestimation or overlook of closed cracks, resulting in potential catastrophic accidents. To solve this problem, several types of nonlinear ultrasonic phased array has been developed by combining nonlinear ultrasonics with phased array (PA). In this study, we introduce the recent progress on nonlinear ultrasonic PA. The first one is called fundamental wave amplitude difference (FAD), which is based on the nonlinear incident-wave-amplitude dependence of fundamental responses. The key to the success of FAD is how high incident wave amplitude can be generated in samples to cause the contact vibration of crack faces. However, increasing the incident wave amplitude at MHz frequencies is not easy. To enhance the applicability of nonlinear ultrasonic PA, we have also developed ultrafast imaging (MHz range) with pump excitation (kHz range). We have successfully captured high-speed crack dynamics using plane wave imaging (PWI) during the pump excitation that can generate a large displacement of more than 1000 nm. Furthermore, we will talk about ongoing work toward 3D crack imaging. [Work partially supported by JSPS KAKENHI (19K21910, 21H04592, 22K18745) and JST FOREST program (JPMJFR2023).]

The universal luminescence behavior of three-level system

The universal luminescence behavior of three-level system is studied. Through theoretical analysis, the population of each energy level under different pump powers could be obtained. Further, the power decay rate coefficient (kD) was proposed and analyzed. The kD represents the effect of the excitation pump power on the decay process of S2, and it is universal available either under weak or intense excitation powers. Besides, the population of S2 could be described by the ratio of kD to the total decay rate. The above analysis could be verified through the experiment.

LoRaWAN-based Petroleum Pipeline Leakage Detection System Using Pressure Profile under a Pump Proximity Effect Condition

Leakages in pipeline is an important problem that can occur at any stage of the pipeline lifespan due to ageing, improper installation, or human related factors like bunkering or vandalization. Several invasive and non-invasive techniques are being used which have proven to be successful. However, this study focuses on leakage in an area of the pipeline network that is most often overlooked. This area is within the first 100 meters of the pipeline network to the excitation pump and is often prone to leakages due to high pressure. This study shows that even at no leak conditions pressure profile of a short pipeline in a closed loop configuration can vary by as much 59.93 percent. The study also examined the impact of single leak, double leaks, and triple leaks on the pipeline network with pressure loss compared to the no leak condition ranging from about 10 percent to as high as 60 percent.

All-fiber all-optical phase controller based on F-P interferometer and Er/Yb co-doped fiber

All-optical devices have attracted much attention for its potential applications in optical communication. In this letter, we propose an all-fiber all-optical phase controller based on an active Fabry-Perot interferometer (FPI) with Er/Yb co-doped fiber (EYDF). Two sections of EYDFs generate a large amount of heat under the pumping excitation of 973 nm, and achieve refractive index change and phase shift of F-P cavity via the thermo-optic effect. Experimental results show that the maximum phase shift of fabricated device is 2.53 π with a slope of 0.0167 π/mW, as well as the phase shift can be converted into the variations of light intensity by the interference characteristic of FPI, enabling optical switching with a rise time of 221 ms. The design of all optical fiber without material coating makes the device has advantages of simple manufacturing, small footprint, especially with good long-term environmental stability. We believe this scheme may provide a new platform for the investigation of all-fiber all-optical modulation, with potential applications in the field of tunable optical filters and Q-switched lasers.

Thermal diffusivity measurement of undoped Yb2O3 oxide by self-made photoacoustic cell

Photoacoustic spectroscopy is an essential technique for material characterization by measuring acoustic noise inside a cell. In this work, we have fabricated a photoacoustic cell and a pre-amplifier circuit and optimized both for maximum sensitivity. The cavity volume is measured ∼4.90 × 10−6 m3 at optimum condition. After that, the thermal diffusivity of undoped ytterbium oxide is measured by recording photoacoustic voltages. It is found 42.22–44.90 mm2/s for the excitation pump power 150–300 mW range by 980 nm diode laser source.

Magnetic Conduction Structure Design and Charging Test of a Linear-Motor Type Flux Pump for Through-Dewar Excitation of High Temperature Superconducting Motors

High temperature superconductivity (HTS) flux pump can be used as the exciter to inject direct current into the superconducting excitation coil of a synchronous motor, without current lead and with low thermal efficiency, which will reduce the cryogenic volume and improve the efficiency of HTS synchronous motor. However, the flux pump has non-negligible thermal impact when it is running continuously for a long time within the cryogenic Dewar, which will cause a heavy heat burden to the cryogenic system. Therefore, based on the linear-motor type flux pump previously invented in our laboratory, this paper improved its magnetic circuit, so that it can introduce the travelling magnetic wave into the Dewar from outside. Firstly, we have used COMSOL Multiphysics to simulate and optimize the waveform of this flux pump. Secondly, we have manufactured the flux pump and magnetic conduction structure, and have tested its performance in liquid nitrogen at 77 K, a pumped DC current of 216 A was measured with a single 12 mm wide YBCO stator. These work have further optimized the linear-motor type flux pump, which provide a contactless static excitation device (CSED) for the 16.9 kW HTS synchronous motor built in our laboratory.