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Comparison between 403 nm and 497 nm repumping schemes for strontium magneto-optical traps
摘要： The theoretical description of the external degrees of freedom of atoms trapped inside a magneto-optical trap (MOT) often relies on the decoupling of the evolution of the internal and external degrees of freedom. That is possible thanks to much shorter timescales typically associated with the first ones. The electronic structure of alkaline-earth atoms, on the other hand, presents ultra-narrow transitions and metastable states that makes such an approximation invalid in the general case. In this article, we report on a model based on open Bloch equations for the evolution of the number of atoms in a magneto-optical trap. With this model we investigate the loading of the strontium blue magneto-optical trap under different repumping schemes, either directly from a Zeeman slower, or from an atomic reservoir made of atoms in a metastable state trapped in the magnetic quadrupolar field. The fluorescence observed on the strong 461 nm transition is recorded and quantitatively compared with the results from our simulations. The comparison between experimental results and calculations within our model allowed to identify the existence of the decay paths between the upper level of the repumping transition and the dark strontium metastable states, which could not be explained by electric dipole transition rates calculated in the literature. Moreover, our analysis pinpoints the role of the atomic movement in limiting the efficiency of the atomic repumping of the Sr metastable states.
关键词： cold atoms,magneto-optical trap,repumping schemes,inhomogeneous Bloch equations,alkaline-earth atoms
更新于2025-09-23 15:22:29
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3D Magneto-Optical Trap of Yttrium Monoxide
摘要： We report three-dimensional trapping of an oxide molecule (YO), using a radio-frequency magneto-optical trap (MOT). The total number of molecules trapped is ～1.5 × 104, with a temperature of 4.1(5) mK. This diversifies the frontier of molecules that are laser coolable and paves the way for the second-stage narrow-line cooling in this molecule to the microkelvin regime. Futhermore, the new challenges of creating a 3D MOT of YO resolved here indicate that MOTs of more complex nonlinear molecules should be feasible as well.
关键词： laser cooling,molecular trapping,yttrium monoxide,3D magneto-optical trap
更新于2025-09-23 15:21:21
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Characteristics of a magneto-optical trap of molecules
摘要： We present the properties of a magneto-optical trap (MOT) of CaF molecules. We study the process of loading the MOT from a decelerated buffer-gas-cooled beam, and how best to slow this molecular beam in order to capture the most molecules. We determine how the number of molecules, the photon scattering rate, the oscillation frequency, damping constant, temperature, cloud size and lifetime depend on the key parameters of the MOT, especially the intensity and detuning of the main cooling laser. We compare our results to analytical and numerical models, to the properties of standard atomic MOTs, and to MOTs of SrF molecules. We load up to 2 × 10^4 molecules, and measure a maximum scattering rate of 2.5 × 10^6 s^?1 per molecule, a maximum oscillation frequency of 100 Hz, a maximum damping constant of 500 s^?1, and a minimum MOT rms radius of 1.5 mm. A minimum temperature of 730 μK is obtained by ramping down the laser intensity to low values. The lifetime, typically about 100 ms, is consistent with a leak out of the cooling cycle with a branching ratio of about 6 × 10^?6. The MOT has a capture velocity of about 11 m s^?1.
关键词： magneto-optical trap,ultracold molecules,laser-cooled molecules
更新于2025-09-23 15:21:01
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states of Rb in simultaneous magneto-optical trapping of Rb and Hg
摘要： We report the measurement of the photoionization cross sections of the 5S1/2 and 5P3/2 states of 87Rb in a two-species Hg and Rb magneto-optical trap (MOT) by the cooling laser for Hg. The photoionization cross sections of Rb in the 5S1/2 and 5P3/2 states at 253.7 nm are determined to be 1+4.3 × 10?20 cm2 and 4.63(30) × 10?18 cm2, respectively. To measure the 5S1/2 and 5P3/2 state fractions in the MOT we detected the photoionization rate of the 5P3/2 state by an additional 401.5 nm laser. The photoionization cross section of Rb in the 5P3/2 state at 401.5 nm is determined to be 1.18(10) × 10?17 cm2.
关键词： Hg,laser cooling,Rb,magneto-optical trap,photoionization cross sections
更新于2025-09-23 15:21:01
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Simultaneous photoreduction and Raman spectroscopy of red blood cells to investigate the effects of organophosphate exposure
摘要： Simultaneous photoreduction and Raman spectroscopy with 532 nm laser has been used to study the effects of organophosphate (chlorpyrifos) exposure on human red blood cells. Since in red blood cells, auto-oxidation causes oxidative stress, which, in turn, is balanced by the cellular detoxicants, any possible negative effect of chlorpyrifos on this balance should results in an increased level of damaged (permanently oxygenated) hemoglobin. Therefore, when 532 nm laser, at a suitable power, was applied to photoreduce the cells, only common oxygenated form of hemoglobin got photoreduced leaving the permanently oxygenated hemoglobin detectable in the Raman spectra simultaneously excited by the same laser. Using the technique effects of chlorpyrifos to build up oxidative stress on red blood cells could be detected at concentrations as low as 10 ppb from a comparison of relative strengths of different Raman bands. Experiments performed using simultaneously exposing the cells, along with chlorpyrifos, to H2O2 (oxidative agent) and/or 3-Aminotriazole (inhibitor of anti-oxidant catalase), suggested role of chlorpyrifos to suppress the cellular anti-oxidant mechanism. Since the high level of damaged hemoglobin produced by the action of chlorpyrifos (at concentrations > 100 ppm) is expected to cause membrane damage, atomic force microscopy was used to identify such damages.
关键词： atomic force microscopy,Photoreduction,optical trap,Raman spectroscopy,red blood cells,chlorpyrifos
更新于2025-09-19 17:15:36
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[IEEE 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama) - Toyama (2018.8.1-2018.8.4)] 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama) - A Chip of Pulse-Laser-Assisted Dual-Beam Fiber-Optic Trap
摘要： Compared with the single-beam gradient optical trap, the dual-beam optical trap based on micro-structure eliminates the need for complex optical alignment and offers intrinsic benefits of miniaturization and stabilization, which are crucial for developing a practical sensor. We design a monolithic chip of dual-beam fiber-optic trap which allows extremely accurate alignment of submicron scale between two counter-propagating fiber beams. Based on micromachining technology, the chip featured a V-shaped groove to align the fibers and a rectangular channel to load the particles is experimentally realized. Recent studies have demonstrated that micro-scale particles can be removed effectively from substrate by focused pulse laser beam. To acquire high trapping efficiency and better trapping stability, we propose a new loading method that combinates pulse laser with dual-beam fiber-optic trap. We have fabricated a silica miniature operating rod for initial storage of the microspheres and moved a targeted particle into the effective trapping area of the fiber-optic trap. Optical loading and trapping of a 10 μm polystyrene particle in air are demonstrated and the controllable capturing process avoids any contamination on fiber ends, which ensures the reliability of optical path. We use a microscopic imaging system and image processing method to test the static stability of the captured particle. The static stability of the microspheres is submicron, which is clearly superior to the test results in liquid environment. The rapid loading and manipulation of microspheres in optical trap is significant for its applications in optomechanics and precision force sensing. Our results pave the way for a new class of monolithic and portable optical sensor for inertial measurement.
关键词： micromachining,fiber-optic trap,optical sensor,dual-beam optical trap,pulse laser
更新于2025-09-12 10:27:22
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Laser drilling of micro-holes in single crystal silicon, indium phosphide and indium antimonide using a continuous wave (CW) 1070 nm fibre laser with millisecond pulse widths
摘要： The laser micro-drilling of “thru” holes, also known as via holes, in Si, InP and InSb semiconductor wafers was studied using millisecond pulse lengths from an IPG Laser Model YLR-2000 CW multimode 2 kW Ytterbium Fibre Laser and a JK400 (400 W) fibre laser, both with 1070 nm wavelength. The flexibility of this laser wavelength and simple pulsing scheme were demonstrated for semiconductor substrates of narrow (InSb Eg 0.17 eV) and wide (InP Eg 1.35 eV)) room-temperature bandgap, Eg, with respect to the photon energy of 1.1 eV. Optical microscopy and cross-sectional analysis were used to quantify hole dimensions and the distribution of recast material for all wafers and, for silicon, any microcracking for both (100) and (111) single crystal surface Si wafer orientations. It was found that the thermal diffusivity was not a sufficient parameter for predicting the relative hole sizes for the Si, InP and InSb single crystal semiconductors studied. Detailed observations for Si showed that, between the threshold energies for surface melting and the irradiance for drilling a “thru” hole from the front surface to rear surface, there was a range of irradiances for which micro-cracking occurred near the hole circumference. The directionality and lengths of these microcracks were studied for the (100) and (111) orientations and possible mechanisms for formation were discussed, including the Griffith criterion for microcracks and the failure mechanism of fatigue usually applied to welding of metals. For Si, above the irradiance for formation of a thru-hole, few cracks were observed. Future work will compare similar observations and measurements in other narrow- and wide-bandgap semiconductor wafer substrates. We demonstrated one application of this laser micro-drilling process for the micro-fabrication of a thru hole precisely-located in the centre of a silicon-based atom chip which had been patterned using semiconductor lithographic techniques. The end-user application was a source of magneto-optically trapped (MOT) cold atoms of Rubidium (87Rb) for portable quantum sensing.
关键词： microcrack,InP,Si,Griffith criterion,pulse,atom chip,Ytterbium fibre laser,semiconductor material,Fibre laser,semiconductor wafer,laser drilling,silicon,magneto-optical trap,MOT,via hole,laser micro-drilling,cold atoms,InSb,thru hole
更新于2025-09-12 10:27:22
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An ultrastable laser system at 689 nm for cooling and trapping of strontium
摘要： We present a 689-nm cavity-based laser system for cooling and trapping strontium atoms. The laser is stabilized to a high-finesse cavity by the Pound–Drever–Hall technique, exhibiting a frequency stability in the 10?14 range for averaging times up to 100 s. A cavity drift of 8 kHz per day is mapped out and compensated. At short times, the laser exhibits a linewidth of a few kilohertz. With this laser system, we realize a magneto-optical trap of strontium operated on the narrow inter-combination transition yielding sub-microkelvin temperatures, and demonstrate absorption spectroscopy on the strontium inter-combination line.
关键词： cooling and trapping,magneto-optical trap,strontium,Pound–Drever–Hall technique,ultrastable laser
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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A versatile dual-species Zeeman slower for caesium and ytterbium
摘要： We describe the design, construction, and operation of a versatile dual-species Zeeman slower for both Cs and Yb, which is easily adaptable for use with other alkali metals and alkaline earths. With the aid of analytic models and numerical simulation of decelerator action, we highlight several real-world problems affecting the performance of a slower and discuss effective solutions. To capture Yb into a magneto-optical trap (MOT), we use the broad 1S0 to 1P1 transition at 399 nm for the slower and the narrow 1S0 to 3P1 intercombination line at 556 nm for the MOT. The Cs MOT and slower both use the D2 line (62S1/2 to 62P3/2) at 852 nm. The slower can be switched between loading Yb or Cs in under 0.1 s. We demonstrate that within a few seconds the Zeeman slower loads more than 109 Yb atoms and 108 Cs atoms into their respective MOTs. These are ideal starting numbers for further experiments on ultracold mixtures and molecules.
关键词： caesium,Zeeman slower,dual-species,ytterbium,ultracold atoms,magneto-optical trap
更新于2025-09-04 15:30:14