High Pump Research Articles

Extremely lower lasing threshold in Er3+/Yb3+ co-doped phosphate dual glass microspheres

Erbium-doped glass microsphere laser systems hold significant promise in the applications of bio-medicine and optical fiber sensing. However, their development has been hindered by the relatively high laser pump threshold. In this study, we proposed a unique dual microsphere system where two microspheres are affixed to a single-mode fiber taper and achieved a remarkably low lasing threshold of 19 μW for single-mode laser emission at 1544 nm. This is in sharp contrast with the lasing threshold of 56 μW observed in single microspheres. Our findings represent a significant achievement in the development of low-threshold, compact infrared laser sources for emerging applications in photonics.

Active and hybrid battery thermal management system using microchannels, and phase change materials for efficient energy storage

Efficient battery thermal management (BTM) is key to the safety and performance of Lithium-ion batteries. This study focuses on cooling a module of 15 prismatic Lithium-titanate cells at an 8C discharge rate using finite volume numerical modeling. Initially, the impact of Reynolds numbers and microchannel count on temperature is examined. Then, Phase change materials (PCM) are introduced to increase thermal management efficiency. Three cases for optimizing the hybrid-BTM system are compared: nanoparticles (1%–5% volume fraction), copper foam (93 % porosity), and micro-encapsulated PCM slurry (5%–15 % volume fraction). The results indicate that an increase in microchannels improves the performance evaluation criterion (PEC) by 93.1 %. Additionally, using copper foam increases the PEC by 18.43 %, 17.44 %, 16.53 %, and 16.31 % at Reynolds numbers 800, 1200, 1600, and 2000, respectively. Furthermore, the BTM system using 5 % nanoparticles demonstrates the best performance, reducing the module temperature by 2.41 % in the presence of copper foam and by 1.78 % in the pure state. Moreover, while the MPCM slurry effectively reduces the module temperature to a desirable level, the high pumping costs significantly decrease the PEC. Additionally, the total entropy of the BTM system follows frictional entropy, although thermal entropy effects dominate the PCM.

Evaluation of Mechanical and Thermomechanical Water Vapor Compression Techniques for Enabling High Temperature Lift Hydration-Based Chemical Heat Pumps

Evaluation of Mechanical and Thermomechanical Water Vapor Compression Techniques for Enabling High Temperature Lift Hydration-Based Chemical Heat Pumps

Spectroscopy of resonantly saturated selective reflection from high-density rubidium vapor using the pump-probe technique

We study the resonant saturation of selective reflection at the interface between a transparent dielectric and high-density rubidium vapor on the D2-line. Our estimates suggest that, within the selected atomic density range, the dipole–dipole self-broadening of the line can vary from 13.2 to 39.6 GHz. Two tunable lasers are used as sources of pump and probe beams with orthogonal linear polarizations. The selective reflection spectra of the probe laser beam are studied at different atomic densities and pump beam intensities ranging from 0 to 8.8 kW cm−2. At high pump intensities, narrow structures are observed around the pump beam frequency, which are associated with power broadening effects. Increasing the pump intensity reduces the spectral width and the magnitude of the selective reflection resonances. The intensity dependence of the width and the magnitude is measured. By adjusting the pump intensity, it is possible to control the spectral width and reflectivity.

Exploratory study on low-GWP working fluid mixtures for industrial high temperature heat pump with 200 °C supply temperature

The development of an industrial high temperature heat pump (HTHP) using a subcritical vapor-compression cycle (VCC) for process heat delivery at 200 °C faces significant challenges due to the scarcity of suitable single-component working fluids. These challenges are further compounded by safety, environmental concerns, material and lubrication oil compatibility and cost considerations. In response, this study investigates the potential of various fluid mixtures to meet these stringent criteria. Using the REFPROP and Cantera software libraries, a Python code was developed to simulate a simplified HTHP VCC with an advanced cycle architecture and assess the flammability risks of the proposed mixtures. Ten single-component fluids of two different families of compounds, hydrocarbons (HCs) and hydro(chloro)fluoroolefins (H(C)FOs), were pre-selected as promising candidates as mixture components. From these, over 460,000 binary, ternary, and quaternary mixtures were generated and evaluated for cycle performance. Although no mixture perfectly met all the predefined criteria, a binary blend of cyclopentane and R1336mzz(Z) in a mole fraction of 0.68 and 0.32, respectively, emerged as the most promising candidate. This mixture demonstrated the best balance of performance and safety under the imposed constraints and is selected for further experimental investigation and validation in a specially designed test rig.

MicroRNA-522-3p promotes brain metastasis in non-small cell lung cancer by targeting Tensin 1 and modulating blood-brain barrier permeability

Brain metastases account for more than 50 % of intracranial central nervous system tumors. The blood-brain barrier (BBB) is mainly composed of endothelial cells, which exhibit low endocytosis and high efflux pumps. Although they are connected by continuous tight junctions and serve as a protective insulation, the BBB does not prevent the development of brain metastases from non-small cell lung cancer (NSCLC). Improving understanding on the mechanisms underlying the development of brain metastasis and the differential molecular characteristics relative to the primary tumor are therefore key in the treatment of brain metastases. This study evaluated the differential expression of miR-522-3p in NSCLC and brain metastases using the Gene Expression Omnibus database. NSCLC brain metastasis model was constructed to screen for cell lines that demonstrated high potential for brain metastasis; We also observed differential expression of miRNA-522-3p in the paraffin-embedded specimens of non-small cell lung cancer and brain metastases from our hospital. The molecular biological functions of miRNA-522-3p were verified using 5-ethynyl-2′-deoxyuridine (EdU) proliferation assay and Transwell invasion assays. RNA-seq was employed to identify downstream target proteins, and the dual-luciferase reporter assay confirmed Tensin 1 (TNS1), a protein that links the actin cytoskeleton to the extracellular matrix, as the downstream regulatory target protein. In vitro blood-brain barrier models and co-culture models were constructed to further identify the role of miRNA-522-3p and TNS1; the expression of BBB-related proteins (ZO-1 and OLCN) was also identified. In vivo experiments were performed to verify the effects of miRNA-522-3p on the time and incidence of NSCLC brain metastasis. The results showed significantly high expression in GSE51666; consistent results were obtained in brain metastasis cells and paraffin samples. RNA-seq combined with miRNA target protein prediction demonstrated TNS1 to be directly downstream of miR-522-3p and to be associated with cell proliferation and invasion. By regulating ZO-1 and OCLN expression, mi-522-3p/TNS1 may increase tumor cell penetration through the BBB while decreasing its permeability. In vivo, miR-522-3p was further demonstrated to significantly promote the formation of brain metastases. miR-522-3p/TNS1 can affect BBB permeability and encourage the growth of brain metastases by modifying the BBB TJ proteins. This axis offers new therapeutic targets for the prevention of brain metastasis.

Design and testing of a high power piezo pump for hydraulic actuation

Traditional valve-controlled hydraulic cylinders are usually very inefficient due to power loss through the control valve. An efficient alternative architecture is to distribute power electrically rather than hydraulically to a group of cylinders and drive each cylinder via individual servomotor-driven pumps. This arrangement is called electrohydrostatic actuation. Such actuators are currently available for power ratings of several hundred watts or greater, but not in the sub-100 W range. This paper details the design, simulation and testing of a piezopump which is intended to address this gap. The motivation is for aerospace applications, and in particular accessory actuators used in the landing gear system. The 10–100 W range is a high-power output for a piezopump, and to achieve this a novel design using disc-style reed valves was developed to allow pumping frequencies above 1 kHz. These high frequencies necessitated the development of custom power electronics capable of delivering 950 V peak-peak sine wave excitation to a largely capacitive load. Experimental results show that the piezopump is capable of delivering over 30 W of hydraulic power, and at no-load can deliver up to 2 L/min of flow at 1250 Hz. Future development includes a transition to multi-cylinder pumps, and improved reed-valve modelling to improve the accuracy of simulated performance.

Phase-matched five-wave mixing in zinc oxide microwire

Abstract High-order wave mixing in solid-state platforms gather increasing importance due to the development of advanced lasers and integrated photonic circuit for both classical and quantum information. However, the high-order wave mixing is generally inefficient in solids under weak pump. Here, we observed the presence of phase matching of five-wave mixing (5WM) propagating in a zinc oxide (ZnO) microwire. The 5WM signal is enhanced by 2–3 orders of magnitude under the phase matching conditions, reaching an absolute conversion efficiency of 1.7 × 10−13 when the peak pumping power density is about 106 W/cm2. The propagation of multiple nonlinear signals, including sum frequency generation, third harmonic generation, four-wave mixing etc., benefited from both the large nonlinear coefficients and the wide transparent window of ZnO, implies the possibility of developing cascaded nonlinear process under higher pumping. This study enriches the ZnO platform for integrated nonlinear nanophotonics.

Performance Evaluation of an EI&CI Dual Ionization TOFMS Hyphenated with a Flow Modulated GC×GC System.

The use and compatibility of a dual-ionization TOFMS operating an EI source and a CI source in parallel using a single TOF mass analyzer with flow modulated two-dimensional GC (GC×GC) is described. Important figures of merit of the mass spectrometer that are required for two-dimensional GC hyphenation such as acquisition speed, ion source response, EI/CI switching, the GC transfer, and data alignment are carefully investigated and addressed. Improved fast switching ion optics allow switching in a 100 Hz frequency between EI and CI spectra sampled from the same GC×GC effluent. The spectra quality also influenced by the preseparation, especially of the EI source, is compared to a standard setup operating a single quadrupole MS coupled to the same GC system. Further, two setups including and excluding an additional flame ionization detector are presented. High increments in CI sensitivities are achieved by utilizing the high pumping efficiencies of the CI stage of the used mass spectrometer. By leading high flow ratios of the GC×GC modulation flows toward the CI source, the intensity can be increased by factors of up to 37 while maintaining the pressure balance of the less robust EI source. Finally, thermal desorption GC×GC-EI&CI-TOFMS analyses of traffic emission samples from a federal highway in Germany are executed with the presented setup.

Weak to strong coupling conditions for a microcavity–quantum dot system under incoherent pumping

We theoretically study the power spectra of a microcavity–quantum dot system under incoherent pumping of photons and excitons, considering two models: one with linked cavity loss rate and pumping, and one with independent cavity loss rate and pumping. We investigate the transition from strong to weak coupling under low and high incoherent pumping in each model and determine sets of parameters necessary to achieve these regimes of light–matter interaction. Despite their differences, both models exhibit a sequence of transitions between weak, strong, and weak coupling as the pumping is increased. This prediction has not yet been observed.

Selective laser melting manufacturing and heat transfer performance study of porous wick in loop heat pipe

Porous wicks, characterized by high capillary pumping force, lightweight, and excellent permeability, have been widely used in heat transfer. Currently, porous wicks are fabricated using powder sintering, porous foaming, and solvent volatilization techniques. However, there is the problem that the shape, size, and pore distribution of the porous structure are difficult to control. This paper proposes a novel 3D printing method to fabricate porous wicks using selective laser melting. The unit diameter and length are optimized to obtain a porous wick with high porosity and capillary pumping force. The effect of laser power on the surface morphology and porosity of the porous wick is investigated by modulating the 3D printing process parameters. The results show that the porosity of the porous wick can be regulated by changing the diameter and length of the pore unit. Decreasing the laser processing power and attaching unmelted solid-phase particles to the pore surface can further increase the porosity. When the laser power is 125 W, the unit diameter is 0.4 mm, and the unit length is 0.6 mm, the porous wick has strong capillary pumping force. The 316L porous material is modified by heat treatment to obtain super-hydrophilic properties. The porous wick is applied to the evaporator of the loop heat pipe, which significantly improves the heat transfer performance. When the heat load is 200 W, the evaporator temperature is 57.09 °C, and the thermal resistance is 0.025 °C/W.

Heat pumps to upgrade existing CHP-DHN systems towards new generation thermal networks

District heating networks with combined heat and power systems and renewable energies are one of the most promising solutions for efficient and sustainable energy supply. In many cases, however, especially for district heating networks prior to the 4th generation, significant renovations are required to meet decarbonization targets. In this paper a study is proposed to evaluate the integration of high temperature heat pumps in an existing combined heat and power - district heating plant to reduce fossil fuel consumption and increase the exploitation of renewable energy sources. The plant is currently operating in central Italy and connects more than 1250 users. The identified solution implies lowering the district heating networks operating temperature and supplying power peaks with a high temperature heat pump acting as a booster. Results showed significant improvements in system performance especially in the winter months, due to the greater impact of lowering the temperature level of the district heating network during these months. Overall, the updated scenario allows the overall demand and ground heat losses to be reduced annually by 5.3 % and 13.5 % respectively. This reduces natural gas consumption by 13.3 % and avoids the emission of about 836 tCO2. The analysis provides guidelines for the upgrade of 3rd generation district heating network that can be useful for planning improvements towards newest generation thermal networks.

Experimental investigation and industrial application of a cascade air-source high temperature heat pump

For industrial thermal scenarios where there is no waste heat to recycle, the Air-source High Temperature Heat Pump (ASHTHP) is the only choice to replace the traditional industrial boiler and decrease energy consumption. A cascade ASHTHP has been designed and developed to support 125 °C hot water, which utilizes R410A and R245fa as working mediums. It is not only theoretically simulated and experimentally investigated, but also applied in an electroplating factory in Ningbo, China to provide 120 °C hot water. When the ambient temperature is 20 °C and the output temperature is 125 °C, the experimental heating capacity of the unit is 121.5 kW with a COP of 1.71. During the experimental investigation, the heating capacity attenuation remains within 19.25 %. Through the comparison and verification of the experimental data, the system simulation results have high accuracy with the error controlled within 5 %. When used in the electroplating factory to provide hot water at 120 °C, the cascade ASHTHP units can provide a heating capacity of 480 kW with a COP of 1.8 at the ambient temperature of around 25 °C, which results in annual savings of approximately $123,200 and a payback period of 1.65 years.

Sensitivity analysis on heat pump - mechanical vapor recompression desalination system by recovering waste heat of offshore power converter station

Abstract Offshore wind power converter stations produce massive low-temperature waste heat, which can hardly be used constrained by their offshore location. Therefore, the recovery of the waste heat has been raising widespread concern. Meanwhile, a large amount of fresh water is needed for its cooling system. So, a novel system combining high temperature heat pump and a mechanical vapor recompression system (HP-MVR) was proposed, and sensitivity analysis was performed to optimize it. The heat pump was used to absorb the waste heat and to produce high temperature water. The mechanical vapor recompression system was adopted to produce fresh water and to recover the condensation heat from the steam. In order to determine the impact parameters on the two crucial performance indicators of freshwater production and unit energy consumption, this article introduces a sensitivity analysis method, focusing on analyzing the sensitivity of the three operating parameters of heat pump condensation temperature, saturated water vapor inlet temperature entering the compressor, and freshwater condensation temperature to these two performance indicators. The results show that the sensitivity coefficients of heat pump condensation temperature, saturated water vapor inlet temperature entering the compressor, and freshwater condensation temperature are 1.13, -0.26, and 1.56. So, the freshwater condensation temperature has the most significant effect on freshwater output. Their sensitivity coefficients to unit energy consumption are 1.02, 1.41, and -0.64. The saturated water vapor inlet temperature entering the compressor has the most significant impact on the required power consumption per unit of freshwater. It will give some guidance for the application of low-temperature waste heat in seawater desalination and the reduction of operating costs.

Influence of un-pumped EYDF on statistical properties of random fiber lasers based on Rayleigh scattering

In this paper the influence of un-pumped Erbium-Ytterbium doped fibers (EYDF) on the statistical properties of random fiber lasers (RFLs) with linear cavity based on Rayleigh scattering is investigated. The experimental results show that the probability density function (PDF) of temporal characteristics of both lasers with and without un-pumped EYDF are asymmetrically distributed near threshold and Gaussian distributed far away over threshold. The width of the PDFs first increases and then decreases with pump power when the un-pumped EYDF is not inserted, while the width of the PDFs continuously increases with pump power when the un-pumped EYDF is inserted, which indicates that EYDF insertion makes the laser more stable at lower pump power and more unstable at higher pump power. The radiation with un-pumped EYDF is fully uncorrelated at high pump power. And the radiation without un-pumped EYDF is also fully uncorrelated at high pump power.

Coherent phonons in incommensurate LaVS3 crystal

In this Letter, we investigate coherent phonon dynamics in the incommensurate LaVS3 crystal by femtosecond pump-probe spectroscopy. Two coherent phonon modes are systematically observed in the transient reflectivity, centered at 1.8 and 2.85 THz, respectively, while a third mode centered at 4.5 THz is observed only at high pump fluence. The experimental results obtained at two different polarization configurations as well as a comparison with recent theoretical results allow to assign the two main modes to the interlayer shearing mode and to an intralayer mode, respectively. Two possible assignments are discussed for the third mode, by invoking a possible emergence of nonlinear phonon processes.

Investigation of the role of Cremophor RH 40 and Cremophor EL in the inhibition of efflux pump of Pseudomonas aeruginosa

BackgroundThere is increasing emphasis on restoring the efficacy of existing antibiotics instead of developing new ones. ObjectivesThis study aimed to determine the role of Cremophor EL and Cremophor RH40 in the inhibition of efflux pumps in MDR Pseudomonas aeruginosa strains. MethodsEfflux pump-active MDR strains of P. aeruginosa were identified and confirmed by flow cytometry. The identified efflux-active strains were further subjected to determination of the MIC of ciprofloxacin and the synergistic role of non-ionic surfactants (Cremophor EL and Cremophor RH40) along with ciprofloxacin. ResultsOut of 30 samples, 6 strains displayed high efflux pump activity. Both Cremophor EL and Cremophor RH40 showed efflux pump inhibitory roles. A 4-fold reduction in the MIC values of ciprofloxacin was observed when Cremophor EL was used along with ciprofloxacin, while a 6-fold reduction was observed when Cremophor RH40 was used along with ciprofloxacin. Both compounds showed synergistic effects with ciprofloxacin, ticarcillin and meropenem when used in a 24-well plate efflux pump inhibitory assay. ConclusionThe inhibition of the efflux pump of MDR Pseudomonas aeruginosa by non-ionic surfactants, namely, Cremophor RH40 and Cremophor EL, provided the best strategy to restore the efficacy of ciprofloxacin.

Titanium:sapphire-on-insulator integrated lasers and amplifiers.

Titanium:sapphire (Ti:sapphire) lasers have been essential for advancing fundamental research and technological applications, including the development of the optical frequency comb1, two-photon microscopy2 and experimental quantum optics3,4. Ti:sapphire lasers are unmatched in bandwidth and tuning range, yet their use is restricted because of their large size, cost and need for high optical pump powers5. Here we demonstrate a monocrystalline titanium:sapphire-on-insulator (Ti:SaOI) photonics platform that enables dramatic miniaturization, cost reduction and scalability of Ti:sapphire technology. First, through the fabrication of low-loss whispering-gallery-mode resonators, we realize a Ti:sapphire laser operating with an ultralow, sub-milliwatt lasing threshold. Then, through orders-of-magnitude improvement in mode confinement in Ti:SaOI waveguides, we realize an integrated solid-state (that is, non-semiconductor) optical amplifier operating below 1 μm. We demonstrate unprecedented distortion-free amplification of picosecond pulses to peak powers reaching 1.0 kW. Finally, we demonstrate a tunable integrated Ti:sapphire laser, which can be pumped with low-cost, miniature, off-the-shelf green laser diodes. This opens the doors to new modalities of Ti:sapphire lasers, such as massively scalable Ti:sapphire laser-array systems for several applications. As a proof-of-concept demonstration, we use a Ti:SaOI laser array as the sole optical control for a cavity quantum electrodynamics experiment with artificial atoms in silicon carbide6. This work is a key step towards the democratization of Ti:sapphire technology through a three-orders-of-magnitude reduction in cost and footprint and introduces solid-state broadband amplification of sub-micron wavelength light.

Multivariate optimization effectiveness model of single-longitudinal-mode laser under pre-laser Q-switching regime.

The optimal effectiveness model for optimizing the system parameters was established in this study by combining the optimization function based on the pre-laser Q-switching technique. By introducing boundary conditions to solve the rate equations, the specific process of composite mode selection is analyzed, and the specific pre-laser modulation time interval that enables single-longitudinal-mode laser output is obtained. Furthermore, through the established efficiency evaluation function for single-longitudinal-mode laser output characteristics, with the maximization of single-pulse energy as the objective, an energy efficiency analysis of relevant parameters in the mode selection components is conducted. The model we have established is universal, which can accurately control the pre-laser Q-switching process and reveals the inherent logical relationship of the relevant parameters in composite mode selection. The output characteristics of a single-longitudinal-mode Q-switching laser can be predicted and adjusted under the condition of high pump injection. Both simulation and experimental results confirm the effectiveness of the model.

21.8 W acetylene-filled hollow-core anti-resonant fiberamplified spontaneous emission source at 3.1 µm.

We report a 20-W-level acetylene-filled nested hollow-core anti-resonant fiber (nested HC-ARF) amplified spontaneous emission (ASE) source at 3.1 µm. A 1535 nm hundred-watt wavelength tunable single-frequency fiber laser with a high signal-to-noise ratio and narrow linewidth is built for pumping acetylene molecules. Simultaneously, a homemade 120 µm core diameter eight-tube nested HC-ARF is used as a gas chamber to obtain high pump laser coupling efficiency. The mid-infrared (mid-IR) ASE source output power of 21.8 W is achieved at 3.1 µm through the low-pressure acetylene gas-filled nested HC-ARF, and the slope efficiency is 25.1%. In addition, the ASE source features an excellent beam quality of Mx 2 = 1.16 and My 2 = 1.13. To the best of our knowledge, for the first time, it is a record output power for such mid-infrared ASE sources while maintaining excellent beam quality. This work provides a new way to achieve high-power mid-infrared emission.