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Research of laser cooling by the optical force between light field and the atoms
摘要： The interaction force in the four-waving mixing of a two-level atoms system is analyzed. A new rate equation and the formula of the optical force are obtained. By simulation and analysis with MATLAB software, the impulse curve is obtained. The impulse increases with probe-wave detuning increasing and then tends to saturation. When the Ra-bi frequency takes a certain value, the impulse can obtain relative maximum and the relative maximum increases with the Ra-bi frequency increasing. The relation between the most value and the parameters of Ra-bi frequency and probe-wave detuning is also researched. The impulse occurs minimum when probe-wave detuning is zero and Ra-bi frequency is zero, there is no maximum for the impulse, which is close to 0.02 in?nitely, the lowest temperature that can be reached is 248 μk. In addition, T2/T1 also has a signi?cant in?uence on the impulse.
关键词： Four-wave mixing,Laser cooling,Optical force,Two-level system
更新于2025-09-11 14:15:04
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Analysis and optimization of passive cooling approach for free-standing photovoltaic panel: Introduction of slits
摘要： One of the major issues related to market available silicon based photovoltaic (PV) technologies is the performance drop caused by relatively high PV panel operating temperatures. The proper cooling of PV panels can reduce performance degradation and increase the lifetime of convectional PV panels. This paper investigates architecture modifications to market available silicon PV panels with the introduction of slits on the PV panel surface, which enables the passive cooling of PV panels. Two different arrangements of slits were numerically investigated and followed with the optimization approach. A developed numerical model was derived from the referent numerical model that was experimentally validated. For each considered scenario, a detailed flow and thermal analysis was performed which included optimization regarding minimum average PV cell temperatures. The considered slit types differ with slit orientation, i.e. parallel to PV panel tilt-axis (type-A) and perpendicular to PV panel tilt-axis (type-B). In both cases, a detailed analysis and optimization required ~100 CFD simulations to investigate the effects of different slit sizes and all wind directions. Overall, using the considered slit modifications, the average PV cell temperature could be decreased up to 3 °C, where effective cooling with the proposed modification is only reasonable for wind speeds up to 5 m/s.
关键词： Energy conversion efficiency,Renewable energy,Photovoltaics,Numerical analysis,Passive cooling
更新于2025-09-11 14:15:04
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A single-laser alternating-frequency magneto-optical trap
摘要： In this paper, we present a technique for magneto-optical cooling and trapping of neutral atoms using a single laser. The alternating-frequency magneto-optical trap (AF-MOT) uses an agile light source that sequentially switches between cooling and repumping transition frequencies by tuning the injection current of the laser diode. We report on the experimental demonstration of such a system for 87Rb and 85Rb based on a microintegrated extended cavity diode laser performing laser frequency jumps of up to 6.6 GHz with a tuning time in the microsecond regime and a repetition rate of up to 7.6 kHz. For that, a combination of a feed-forward for coarse frequency control and a feedback for precise locking was used. We discuss the results of the AF-MOT characterization in terms of atom numbers and cloud temperature for different operation parameters.
关键词： alternating-frequency,single-laser,neutral atoms,cooling and trapping,magneto-optical trap
更新于2025-09-11 14:15:04
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Towards a rational design of laser-coolable molecules: insights from equation-of-motion coupled-cluster calculations
摘要： Access to cold molecules is critical for quantum information science, design of new sensors, ultracold chemistry, and search of new phenomena. These applications depend on the ability to laser-cool molecules. Rigorous theory and qualitative models can play a central role in narrowing down the vast pool of potential candidates amenable to laser cooling. We report a systematic study of structural and optical properties of alkaline earth metal derivatives in the context of their applicability in laser cooling using equation-of-motion coupled-cluster methods. To rationalize and generalize the results from high-level electronic structure calculations, we develop an effective Hamiltonian model. The model explains the observed trends and suggests new principles for the design of laser-coolable molecules.
关键词： laser cooling,alkaline earth metal derivatives,effective Hamiltonian model,quantum information science,equation-of-motion coupled-cluster methods,ultracold chemistry
更新于2025-09-11 14:15:04
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Potential of water natural circulation coupled with nano-enhanced PCM for PV module cooling
摘要： This paper introduces a new photovoltaic module passive cooling system that works with natural cooling water circulation. The heat was removed from cooling water by a PCM-based cooling system. A special zig zag geometry of PCM container was considered to increase the heat transfer surface. At the ?rst stage of experiments, a composed oil consisting of 82 wt% coconut oil and 18 wt% sun?ower oil was used as PCM. Then, in order to increase the performance of heat transfer between PCM and cooling water, the composed oil was mixed with Boehmite nanopowder (0.009 (w/w)). The cooling performance of the composed oil and nano - composed oil was assessed by monitoring the temperature and the generated electrical power of the panel at various radiation intensities. The results reveal the reliability of the proposed system for cooling of the PV module without need to any pumping system. Moreover, the results show that using nano - composed PCM is more ef?cient than the plain one. The highest increase in the maximum produced power relative to the reference case were obtained in the presence of nano - composed oil, which were 44.74, 46.63, 48.23% at the radiation intensities of 410,530,690 W/m2, respectively.
关键词： Photovoltaic,PCM,Natural circulation,Passive cooling,Boehmite nanoparticles,Heat transfer
更新于2025-09-11 14:15:04
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Coaxial waterjet-assisted laser drilling of film cooling holes in turbine blades
摘要： Film cooling holes (FCHs) of nickel-based single crystal turbine blades were drilled by 532 nm Nd:YVO4 nanosecond laser in coaxial waterjet-assisted environment. Microstructure of the side wall of the FCHs was mainly investigated by means of transmission electron microscopy. The average thickness of heat affected zone (HAZ) around FCHs decreases with increasing of water flow rate. The main phase within HAZ evolves from β-NiAl to β-NiAl + γ-Ni with the increase in the water flow rate. Some γ-Ni particles in the HAZ twined along (111) plane. A small portion of the FCHs are free of HAZ when drilled by coaxial waterjet-assisted laser drilling at a laminar water flow rate ≥ 3.1 m/s. There are no processing-induced defects including HAZ, microcrack, and phase transformation around the FCHs when drilled at the water flow rate ≥ 5.1 m/s. The FCHs with high surface quality can be drilled by the coaxial waterjet-assisted laser drilling. Finally, effects of fluid water on drilling quality of the FCHs were discussed.
关键词： turbine blades,film cooling holes,Coaxial waterjet-assisted laser drilling,heat affected zone (HAZ),transmission electron microscopy (TEM)
更新于2025-09-11 14:15:04
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Underwater laser hardening of bearing steels
摘要： Water can act as an effective cooling agent during processing of materials. This can be beneficial especially for surface hardening of steels whereby a rapid quenching rate is desired to generate a hard martensitic surface layer. In this study, the underwater laser hardening of bearing steels is experimentally investigated using a fiber laser. The study found that underwater laser hardening increases surface hardness by about 3.5 times than that of the base material which is higher than in conventional laser hardening. Surface hardness as high as 900 HV is achieved when processed with a thin layer of water above the steel surface. However, the depth and width of the laser hardened zone are found to be significantly smaller than in conventional laser hardening. Further analysis revealed that irregular hardened track formed at slower scanning speed due to the convective motion of water and shock wave generation.
关键词： Steel,Water cooling,Hardness,Laser hardening
更新于2025-09-11 14:15:04
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Theoretical study on the low-lying electronic excited states and laser cooling feasibility of AuH molecule
摘要： To evaluate characteristics of the low-lying electronic states and the feasibility of the laser cooling of the AuH molecule, we investigate the potential energy curves (PECs), the vibrational and rotational characteristics of the ground and low-lying excited electronic states based on ab initio calculations. The PECs of the X1Σ+, A1Σ+, B1Σ+, a3Σ+, b3Σ+, e3Σ+, C1П, D1П, c3П and d3П states and the transition dipole moments among these states are calculated with the multi-reference configuration interaction method with Davidson correction and all-electron basis sets. Based on the obtained PECs, the Schr?dinger equations of nuclear movement are solved to obtain the rotational and vibrational energy levels of the electronic states. The spectroscopic parameters are obtained by fitting the obtained rotational and vibrational levels with Dunham series expansion. The matrices of the Franck-Condon factors (FCFs) dependent on the vibrational quantum numbers are obtained. The feasibility of laser cooling is explored. The FCF of the D1П (v′ = 0) ? X1Σ+ (v″ = 0) transition is 0.9862, which implies that the AuH molecule is feasible but not the much better ones for laser cooling and more pumping lasers are needed. The optical laser cooling scheme is suggested and the Einstein coefficient and the recoil temperature are calculated to evaluate the effect of the cooling scheme.
关键词： Franck-Condon factor,recoil temperature,laser cooling scheme,transition dipole moment,low-lying excited states
更新于2025-09-11 14:15:04
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Polarisation of Light || PHENOMENA PRODUCED BY MECHANICAL MEANS—UNANNEALED GLASS
摘要： The chapter discusses the phenomena produced by mechanical means on unannealed glass, focusing on how mechanical strain can impart a structural character to glass analogous to that of a crystal, affecting the motion of the ether within it and exhibiting chromatic effects with polarised light. It describes experiments involving straining a rectangular bar of ordinary glass and observing the light passing through it, as well as the effects of squeezing a thick square plate of glass in a vice. The chapter also explores the impact of molecular forces due to heat and cooling on glass, and the permanent, splendid effects produced by unannealed glass that has been rapidly and unequally cooled.
关键词： crystal,polarisation,light,molecular forces,unannealed glass,mechanical means,pressure,heat,strain,chromatic effects,cooling
更新于2025-09-11 14:15:04
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Entanglement versus cooling in the system of a driven pair of two-level qubits longitudinally coupled with a boson mode field
摘要： The relationship among the entanglement creation within coherently pumped and closely spaced two-level emitters longitudinally coupled with a single-mode boson field, and the subsequent quantum cooling of the boson mode is investigated. Even though the two-level qubits are resonantly driven, we have demonstrated an efficient cooling mechanism well below limits imposed by the thermal background. Furthermore, the cooling effect is accompanied by entanglement of the qubit pair components when the dipole-dipole frequency shift is close to the frequency of the boson mode. The maximum boson mode cooling efficiency realizes on the expense of the entanglement creation. Importantly, this occurs for rather weak external pumping fields protecting the sample from the deteriorations. Finally, the conditions to effectively optimize these effects are described as well.
关键词： entanglement,boson mode,dipole-dipole interaction,two-level qubits,cooling
更新于2025-09-11 14:15:04