Cavity Pump Research Articles

A novel design on smooth rotor profile with meshing clearance for screw vacuum pump

Cross-section profile of rotor takes a great effect on the performance of dry-screw vacuum pump. A novel smooth rotor profile consisting of eight segments of curves, including arcs and conjugate correction curves is proposed. Advantages are that it can be used to solve the unsmooth connection and no meshing clearance in traditional profile. The meshing model for new profile can directly generate stable addendum clearance, tooth clearance, tooth side clearance, and radial clearance. The influences of the epicycloid rotation angle, arc radius and involute offset distance of the conjugate correction curve on the clearances are studied according to established theoretical model. And transient flow field of vacuum pump is analyzed by using the commercial software Ansys-Fluent®. Compared to traditional screw vacuum pump, the results shows that pressure in inlet and pump cavity is lower, and maximum pumping speed is higher, indicating that the proposed design is superior.

Numerical Simulation of Internal Flow Field of Self-Designed Centrifugal Pump

The two self-designed of centrifugal pump with small vane and centrifugal pump without small vane were simulated numerically to select a centrifugal pump with higher efficiency. The internal flow characteristics of the centrifugal pump was simulated by using Reynolds time-averaged N-S equation and RNG turbulence model to obtain pressure and velocity distribution and the cavitation characteristics were simulated by using SST turbulence model and Schnerr-Sauer cavitation model to obtain the gas volume fraction distribution. The results show that at the same flow rate, the change of velocity in the pump cavity of centrifugal pump with vane is smoother and the gas volume is less, but the back-flow is aggravated near the small vane, especially when interacting with the tongue, and a large amount of gas is generated at the suction surface of the small vane. In addition, the efficiency of centrifugal pump without vane is higher than that of centrifugal pump with vane, which provides a basis for the structural optimization of centrifugal pump.

Finite-temperature Dicke phase transition and the collapse of superradiant phase in an optomechanical-atomic cavity

We mainly investigate Dicke phase transition at finite temperature in an optomechanical-atomic cavity by means of the functional path-integral approach. By the thermodynamic equilibrium equation, the mean photon number, the scaled atomic population, the mean phonon number, the average energy and the rich phase diagram are depicted in the existence of the nonlinear atom–photon interaction, the nonlinear photon–photon coupling strength, the pump–cavity detuning and the finite temperature. Beside Dicke phase transition from the normal phase (NP) to the superraidant phase (SP) at finite temperature, the collapse of the SP and the dynamically unstable state (DUS) are revealed showing the effects of the photon–phonon coupling strength ξ and nonlinear atom–photon interaction U. Meanwhile, a new phase transition occurs from the SP to the dynamically unstable state (DUS) at the turning point gt with the existence of ξ or U. The region of the SP can be completely eliminated by the mechanically and thermally stimulated photon-emission. The entropy and corresponding specific heats are presented to demonstrate the corresponding critical behavior at the phase transition point.

Dynamic behaviors of blade cavitation in a water jet pump with inlet guide vanes: Effects of inflow non-uniformity and unsteadiness

The waterjet pump cavities would unavoidably interact with inlet guide vanes (IGVs) wakes and thus to bring about dynamic loading impingements. This work jointly conducts experiments, numerical simulations, and time-frequency analysis to shed light on the dynamic behaviors of blade cavitation under the IGVs perturbations. As observed, the blade cavitation subjected to a lower incidence angle presents a highly dynamic pattern, which non-uniformly develops and globally performs a typical periodic cycle of generation, developing, and collapsing as each blade passes through the IGVs wake in sequence. At the same instant, the cavitation patterns on the adjacent blade would perform a distinctive tendency due to the initial phase difference. It is illuminated that the spatial-temporal incidence angle determined by inflow non-uniformity and unsteadiness majorly contribute to the uneven and intermittent development of blade cavitation. The cavitation evolutions and excited pressure and thrust deterministically oscillate with the IGVs passing frequency. The resultant cavity variations would additionally introduce broadband low-frequency thrust fluctuations that are interpreted as the non-uniform loading impacts on the blade surface. This work comparatively studies the dynamic behaviors of blade cavitation that are commonly encountered for a pump with inflow distortions, which aims to provide a fundamental understanding for cavitation dynamics in pumps.

Intracavity optical parametric oscillator: Model of dynamic system with different values of time delay for pump and signal radiation

Most of intracavity pumped optical parametric oscillators (OPO) are made nowaday according to a scheme with a single-resonance OPO located in the cavity of a pump laser. Usually the cavities of the pump and OPO (signal) emission have different values of round-trip time (delay). Aim of the study is therefore to build up the mathematical model of intracavity optical parametric oscillator (ICOPO) considered as a time-delay dynamic system with two values of delay in both cavities (the pump and signal). Methods. The model allows to analyze the steady state (equilibrium point) of the dynamic system and its stability with the help of characteristic equation’s solution. Results. Countless set of the characteristic equation roots is shown to consist of complex-conjugate pairs with imaginary parts which are nearly multiples of intermode beat frequencies in the pump and signal cavities. The diagram of stability depending on the position of nonlinear crystal in the resonator was built on the parameter plane. Features of the plane partition into the areas of stability/instabilty vs behavior of the characteristic equation roots are examined. Discussion. The results of the study allow to consider an ICOPO as the time-delay dynamic system thus adding to the physical picture of intracavity parametric oscillators.

Charge sensitivity of a cavity-embedded Cooper pair transistor limited by single-photon shot noise

Using an operator scattering approach, we analyze the quantum dynamics of an ultrasensitive electrometer—a Cooper pair transistor embedded in a quarter-wave microwave cavity (cCPT). While the cCPT is inherently a tunable, strongly nonlinear system affording a diverse range of functionalities, we restrict our present analysis to a necessary first investigation of its linear charge sensing capabilities, limiting to low pump powers corresponding to an average cavity photon number of ≲1. Assuming realizable cCPT parameters [B. L. Brock et al., Phys. Rev. Applied 15, 044009 (2021)], and not including noise from the subsequent amplifier chain, we predict the fundamental, photon shot noise-limited charge sensitivity to be 0.12μe/Hz when the pumped cavity has an average of one photon and the cCPT is operated close to charge degeneracy. This is to be compared with a first reported charge sensitivity value of 14μe/Hz in the single-photon regime [B. L. Brock et al., arXiv:2102.05362 (2021)].

Zigzag Multirod Laser Beam Merging Approach for Brighter TEM00-Mode Solar Laser Emission from a Megawatt Solar Furnace

An alternative multirod solar laser end-side-pumping concept, based on the megawatt solar furnace in France, is proposed to significantly improve the TEM00-mode solar laser output power level and its beam brightness through a novel zigzag beam merging technique. A solar flux homogenizer was used to deliver nearly the same pump power to multiple core-doped Nd:YAG laser rods within a water-cooled pump cavity through a fused silica window. Compared to the previous multibeam solar laser station concepts for the same solar furnace, the present approach can allow the production of high-power TEM00-mode solar laser beams with high beam brightness. An average of 1.06 W TEM00-mode laser power was numerically extracted from each of 1657 rods, resulting in a total of 1.8 kW. More importantly, by mounting 399 rods at a 30° angle of inclination and employing the beam merging technique, a maximum of 5.2 kW total TEM00-mode laser power was numerically extracted from 37 laser beams, averaging 141 W from each merged beam. The highest solar laser beam brightness figure of merit achieved was 148 W, corresponding to an improvement of 23 times in relation to the previous experimental record.

Compact, 2.95-GHz repetition-rate femtosecond optical parametric oscillator with tunable pulse repetition frequency

We report a compact femtosecond optical parametric oscillator (OPO) with a tunable repetition rate that is harmonically pumped using a 52.5 MHz Yb-doped fiber laser system. By reducing the OPO cavity length, the repetition rate can be adjusted successively from 1.935 to 2.95 GHz at 52.5 MHz intervals. The multiplication of the repetition rate is achieved by placing a nonlinear crystal in a compact linear cavity, and the minimum cavity length is 47.8 mm. The maximum signal power (205.2 mW) at 2.04 GHz is obtained at an input pump power of 2.35 W and a central wavelength of 1472 nm. The central wavelength of the signal pulses can be tuned from 1383 to 1596 nm. To the best of our knowledge, 2.95 GHz is the highest repetition rate achieved using a femtosecond OPO based on an ultrashort cavity with a length that is N times (N is an integer) shorter than that of the pump cavity.

Mutual cooperative effects between the mode components of two-photon and Raman induced cavity lasing processes

The paper proposes to unify the two-photon laser and induced cooperative scattering Raman lasing in which the flying ensemble of two-level excited radiators are coupled with the bimodal cavity field in nonlinear two-photon and scattering interactions. It discusses the situation in which the induced two-quantum lasing takes place together with the cooperative scattering conversion of photons between the pump, Stokes, and anti-Stokes cavity modes. The proposed master equation describes cooperative energy exchanges between Raman and two-photon lasing processes by portions of energies multiple to the energy of the entangled photon pair.The generators of such emission and absorption processes belonging to the symmetries of Raman conversion and two-photon cooperative generation are unified. The first symmetry belongs to su(2) algebra connected to the scattering conversion in the Stokes, pump, and anti-Stokes modes of cavity (Opt. Commun.,285(5) (2012) 686–692). The second one belongs to multi-mode su(1,1) symmetry which quantifies the cooperative process belonging to two-photon emission in cavity/fiber mode components of field (see Opt. Commun. 247(4–6) (2005) 381–392). The bimodal collective photon operators are introduced describing the emission or absorption acts of the fixed portion of energy from the cavity equal to the transition energy between the states of each excited atom. A key impact of the study focuses on the statistical properties of the bimodal field and their detection possibilities are proposed for the description of the time evolution of quantum correlations between the field components of Raman conversion and two-photon emission.

Seven-Rod Pumping Approach for the Most Efficient Production of TEM00 Mode Solar Laser Power by a Fresnel Lens

Abstract A seven-rod/seven-TEM00 mode beam Fresnel lens solar laser pumping approach is here proposed. The Fresnel lens with 4.0 m2 collection area was used as the primary solar concentrator to pump seven 2.5 mm diameter, 15 mm length Nd:YAG rods within a conical pump cavity through a secondary fused silica aspheric concentrator. Within the pump cavity, solar pump rays not completely absorbed by one of the seven rods were furtherly absorbed by other rods, ensuring hence a high absorption efficiency and avoiding the serious thermal lensing and thermal stress issues associated with classical large rod solar lasers. Seven individual plane-concave large-mode resonators were adopted to enable a good overlap between solar pump mode and TEM00 laser oscillating mode. By using both zemax® and lascad® software, the maximum total TEM00 mode solar laser power of 54.65 W was numerically calculated by optimizing the radius parameter of the Fresnel lens, the diameter of the laser rod, and the radius of curvature of the laser resonator output mirror. TEM00 mode solar laser collection efficiency of 13.66 W/m2 and solar power-to-TEM00 mode laser power conversion efficiency of 1.44% were calculated, representing substantial enhancements of 4.66 times and 4.38 times, respectively, as compared with previous experimental records of the TEM00 mode solar laser pumped through a Fresnel lens with 0.785 m2 collection area. The feasibility of TEM00 mode solar laser power delivery by hollow-core photonic crystal fibers was finally studied.

Renovating electrical power-to-TEM00 mode laser power conversion efficiency with four-lamp/four-rod pumping scheme

One of the major drawbacks in lamp-pumped laser development resides in its low electrical input-to-TEM00 mode laser conversion efficiency. Here is proposed a four-lamp/four-rod solid-state laser pumping concept. Four Nd:YAG rods were pumped by four 1.0 kW input power Krypton CW arc lamps within a quadruple ellipse pump cavity, ensuring a good absorbed pump power distribution within each rod. The laser design parameters were optimized in Zemax® and LASCAD® software to maximize the TEM00 mode laser power. 35.80 W TEM00 mode total laser power was numerically calculated, corresponding to 0.90% electrical input-to-TEM00 mode laser conversion efficiency and 2.25 times improvement over that of the state-of-the-art lamp-pumped laser. For the extraction of a single TEM00 mode laser beam, a novel laser cavity was presented. 25.94 W laser beam brightness figure of merit was numerically calculated, corresponding to a 4-fold increase over that from each of the four TEM00 mode laser beams.

Quasi-Gaussian Multibeam Solar Laser Station for a Megawatt Solar Furnace

An alternative multirod solar side-pumping concept for the production of multiple quasi-Gaussian beams is proposed. This scheme was based on the One-Megawatt solar furnace in Odeillo, France, which collected and concentrated the solar light into a multilayered pyramidal pumping cavity placed at the focal zone. Each layer was comprised of a square array of four laser heads, each composed of a biconic surface that reflected the solar rays towards a Nd:YAG rod fixed inside a fused silica flow tube. A pyramidal reflector was placed inside the pumping cavity to close it and maximize the harness of solar energy. Compared to the previous multibeam solar laser station design for the same solar furnace, considerable alleviation of thermal lensing effects was achieved with the present approach, allowing the improvement of the laser beam quality factors and, consequently, the possibility of a 32-laser-beam generation, each with a quasi-Gaussian profile. For this case, 9.44 kW total laser power was calculated. Additionally, 20.01 kW total multimode laser power was numerically determined, which corresponds to a 10.93 W/m2 collection efficiency and a 2.0% solar-to-laser power conversion efficiency.

Quasi-Gaussian Multibeam Solar Laser Station for a Megawatt Solar Furnace

An alternative multirod solar side-pumping concept for the production of multiple quasi-Gaussian beams is proposed. This scheme was based on the One-Megawatt solar furnace in Odeillo, France, which collected and concentrated the solar light into a multilayered pyramidal pumping cavity placed at the focal zone. Each layer was comprised of a square array of four laser heads, each composed of a biconic surface that reflected the solar rays towards a Nd:YAG rod fixed inside a fused silica flow tube. A pyramidal reflector was placed inside the pumping cavity to close it and maximize the harness of solar energy. Compared to the previous multibeam solar laser station design for the same solar furnace, considerable alleviation of thermal lensing effects was achieved with the present approach, allowing the improvement of the laser beam quality factors and, consequently, the possibility of a 32-laser-beam generation, each with a quasi-Gaussian profile. For this case, 9.44 kW total laser power was calculated. Additionally, 20.01 kW total multimode laser power was numerically determined, which corresponds to a 10.93 W/m2 collection efficiency and a 2.0% solar-to-laser power conversion efficiency.

Analysis of Vase Shaped Pumping Cavity for Solar-Pumped Laser

Although sunlight is a promising renewable energy source, the light is incoherent and difficult to use directly. Therefore, a solar-pumped laser, which directly converts sunlight into coherent laser light of, is a promising technology. A solar-pumped laser collects sunlight into the laser medium to realize laser oscillation. In order to realize an efficient solar-pumped laser system, it is necessary to design a pumping cavity that absorbs maximal sunlight into the laser medium with minimal thermal shock. In this research, the pumping cavity shape was studied using a numerical ray tracing simulation. As a result, it was found that a cone shaped pumping cavity can be expected to improve the absorption rate by approximately 30% over a cylindrically shaped pumping cavity. Furthermore, the absorption power density distribution can be flattened by a vase shaped pumping cavity, while maintaining the same absorption efficiency. The vase shaped pumping cavity has almost half the dispersion of the absorbed power density in the laser medium when compared with the cone shaped pumping cavity.

Examining axion-like particles with superconducting radio-frequency cavity

We address production of massive axion-like particles by two electromagnetic modes inside a superconducting radio-frequency (SRF) cylindrical cavity. We discuss in detail the choice of pump modes and cavity design. We numerically compute time-averaged energy density of produced axion field for various cavity modes and wide range of axion masses. This allows us to estimate optimal conditions for axion production within a cavity. In addition, we consider photon regeneration process initiated by produced axion field in a screened radio-frequency cavity and derive constraints in parameter space (gaγγ, ma) for different choice of pump modes.

Numerical study of a ring-array-concentrator for Nd:YAG solar laser pumping

In this paper, we report a numerical study of a Nd:YAG solar laser side-pumped by a ring-array concentrator (RAC) system. We used the ZEMAX© and LASCAD© software to optimize a 1.5-m diameter RAC system, a 3V-shaped pump cavity within which a Nd:YAG single-crystal laser rod (4-mm diameter, 30-mm length) is mounted, and the laser resonator parameters. The multimode solar laser output power was numerically calculated to be 34.8 W in a continuous-wave mode, corresponding to a solar laser collection efficiency of 19.69 W/m2, a slope efficiency of 3.07%, and 2.3% solar-to-laser conversion efficiency, indicating an improvement of 2.05, 1.31, and 1.5 times, respectively, relative to that of the previous results for a side-pumped Nd:YAG solar laser. Moreover, this study is the first numerical analysis of a Nd:YAG solar laser side-pumped by a RAC concentrator.

Metamorphosis of Goldstone and soft fluctuation modes in polariton lasers

For a driven-dissipative quantum many-body system prepared in a spontaneous broken-symmetry steady state, in addition to the Goldstone mode, the soft fluctuation modes provide important insight into the system's dynamics. Using a microscopic polariton laser theory, we find a rich transformation behavior of discrete and continuum soft modes in a two parameter (pump density and cavity dissipation rate) space. Our theory yields a unified picture of a variety of seemingly disconnected physical concepts including Mott transition, Mollow spectra or relaxation oscillations, polaritonic Bardeen-Cooper-Schrieffer gaps, and Goldstone companion modes. In particular, transformation paths connect the Goldstone companion modes with the Mollow analog modes across a line of exceptional points.

Ce:Nd:YAG side-pumped solar laser

A significant advancement in the Ce:Nd:YAG solar laser performance using a side-pumping configuration is reported. A solar laser head was composed of a double-stage semispherical lens and a trapezoidal-shaped pumping cavity, which coupled and redistributed the concentrated solar radiation from the focal zone of a parabolic mirror into a laser rod. The laser output performance of a 4.0-mm diameter, 35-mm length Ce:Nd:YAG laser rod was tested and compared with that from a Nd:YAG rod with the same dimensions. At an incoming solar power of 600 W, the Ce:Nd:YAG solar laser achieved 23.6-W / m2 collection efficiency, 4.4% slope efficiency, and 2.8% solar-to-laser power conversion efficiency, which are 1.57, 1.47, and 1.56 times, respectively, higher than the ones obtained with the Nd:YAG rod. The Ce:Nd:YAG side-pumped solar laser has also 1.39 and 1.15 times more collection efficiency and solar-to-laser power conversion efficiency, respectively, than the previous record by Nd:YAG side-pumped solar laser. We demonstrate the great potential of the Ce:Nd:YAG ceramic rod as a gain medium for side-pumped solar lasers.

Study on Improving Cavitation Performance of Centrifugal Pump by Perforation at the Front Cover Plate

To improve the cavitation performance of a centrifugal pump, the high-pressure liquid in the front pump cavity is introduced into the cavitation area on the back of the blade by perforated holes at the front cover of the impeller. Based on the RNG k-ε turbulence model and Zwart-Gerber-be1amri cavitation model, the numerical calculation and analysis of the cavitation flow field in the model before and after perforation under different cavitation numbers is carried out by FLUENT. The results show that: The perforation at the front cover plate can effectively improve the pressure value of the cavitation area on the back of the blade. To some extent, the change of pressure gradient restrains the development of cavitation. The perforation at the front cover plate can effectively reduce the integral value of the cavitation bubble in the passage, improve the flow passage conditions in the impeller passage, and reduce the blockage degree of the cavitation to the passage. At the same time, the fluctuation range of the cavitation volume in the impeller is small in a rotation cycle after the perforation. It can be seen that the way of perforation at the front cover plate can effectively improve the cavitation performance of the centrifugal pump.

Six-rod/six-beam concept for revitalizing TEM00 mode lamp-pumped lasers

Low lamp input-to-TEM00 mode laser output conversion efficiency and strong thermal lensing effects are bottleneck issues in commercially available single-rod/single-beam lamp-pumped lasers. A six-rod/six-beam concept is proposed to substantially enhance lamp input-to-TEM00 mode laser output conversion efficiency. A 4-kW-single-thick arc lamp was used to efficiently pump six thin Nd:YAG rods simultaneously within a modified two-ellipse pump cavity. All of the design parameters were numerically optimized by Zemax® and LASCAD® software. Since each rod absorbed only a small part of the lamp power, significantly reduced thermal lensing and thermal stress problems were predicted. Asymmetrical laser resonators were adopted to enable a large mode-matching between the lamp pump mode and the fundamental laser mode within each rod. 34.82-W total TEM00 mode laser power was numerically calculated, corresponding to 0.87% lamp input power-to-TEM00 mode laser power conversion efficiency and a 2.18 times improvement over that of the state-of-the-art lamp-pumped laser. A TEM00 mode power-to-multimode power ratio of 59.0% was also obtained, being 2.40 times more than that of the most efficient single-rod TEM00 mode lamp-pumped laser. Six TEM00 mode laser beams emitting from the single laser head may provide a cost-effective laser solution to several processes in industry and scientific research. For the extraction of a single TEM00 mode laser beam, a laser resonant cavity with folding mirrors was also presented. A 15.34-W laser beam brightness figure of merit was numerically calculated, corresponding to a 13-fold increase over that from each of the six TEM00 mode laser beams.