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arXiv:2412.11411

A Rb-Cs dual-species magneto-optical trap

Shi-Yao Shao, Qing Li, Lihua Zhang, Bang Liu, Zheng-Yuan Zhang, Qifeng Wang, Zhang, Jun, Yu Ma, Han, Tian-Yu, Han-Chao Chen, Jia-Dou Nan, Yi-Ming Yin, Dongyang Zhu, Yajun Wang, Dong-Sheng Ding, Bao‐Sen Shi

Published Dec 16, 2024• 0 citations
arXivHTMLPDF

Abstract

We describe a three-dimensional (3D) magneto-optical trap (MOT) capable of simultaneously capturing 85Rb and 133Cs atoms. Unlike conventional setups, our system utilizes two separate laser systems that are combined before entering the vacuum chamber, enabling the simultaneous trapping of two different atomic species. Additionally, in our 3D MOT configuration, two (of three) pairs of laser beams are not orthogonal to the chamber surfaces but are aligned at a 45° angle. With a total trapping laser power of 8 mW and repump laser power of 4 mW for Rb atoms, and a total trapping laser power of 7.5 mW and repump laser power of 1.5 mW for Cs atoms, we achieve optical depths (OD) of 3.71 for Rb and 3.45 for Cs, demonstrating efficient trapping for both species. Our 3D MOT setup allows full horizontal optical access to the trapped atomic ensembles without spatial interference from the trapping or repump laser beams. Moreover, the red detuning for trapping both atomic species is smaller than in traditional configurations. This system offers a versatile platform for exploring complex phenomena in ultracold atom physics, such as Rydberg molecule formation and interspecies interactions.

DOI
10.48550/arxiv.2412.11411

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We describe a three-dimensional (3D) magneto-optical trap (MOT) capable of simultaneously capturing 85Rb and 133Cs atoms. Unlike conventional setups, our system utilizes two separate laser systems that are combined before entering the vacuum chamber, enabling the simultaneous trapping of two different atomic species. Additionally, in our 3D MOT configuration, two (of three) pairs of laser beams are not orthogonal to the chamber surfaces but are aligned at a 45° angle. With a total trapping laser power of 8 mW and repump laser power of 4 mW for Rb atoms, and a total trapping laser power of 7.5 mW and repump laser power of 1.5 mW for Cs atoms, we achieve optical depths (OD) of 3.71 for Rb and 3.45 for Cs, demonstrating efficient trapping for both species. Our 3D MOT setup allows full horizontal optical access to the trapped atomic ensembles without spatial interference from the trapping or repump laser beams. Moreover, the red detuning for trapping both atomic species is smaller than in traditional configurations. This system offers a versatile platform for exploring complex phenomena in ultracold atom physics, such as Rydberg molecule formation and interspecies interactions.
Abstract We describe a three-dimensional (3D) magneto-optical trap (MOT) capable of simultaneously capturing 85Rb and 133Cs atoms. Unlike conventional setups, our system utilizes two separate laser systems that are combined before entering the vacuum chamber, enabling the simultaneous trapping of two different atomic species. We trapped 85Rb and 133Cs atoms using relatively low total power: 8 mW cooling and 4 mW repump for 85Rb, and 7.5 mW cooling and 1.5 mW repump for 133Cs. The number of trapped atoms was 1.6 × 108 for 85Rb and 1.4 × 108 for 133Cs. The optical depths were 3.71 for 85Rb and 3.45 for 133Cs. The temperature of trapped atoms was ∼200 μK for 85Rb and ∼200 μK for 133Cs. Our 3D MOT setup allows full horizontal optical access to the trapped atomic ensembles without spatial interference from the trapping or repump laser beams. Our vacuum system is also quite simple, avoiding much of the complexity typically encountered in similar dual-species systems. However, the red detuning of the cooling laser used for atomic trapping in our system is relatively small, leaving room for further optimization. This system offers a versatile platform for exploring complex phenomena in ultracold atom physics, such as Rydberg molecule formation and interspecies interactions.
We describe the apparatus of a dark-line two-dimensional (2D) magneto-optical trap (MOT) of (85)Rb cold atoms with high optical depth (OD). Different from the conventional configuration, two (of three) pairs of trapping laser beams in our 2D MOT setup do not follow the symmetry axes of the quadrupole magnetic field: they are aligned with 45° angles to the longitudinal axis. Two orthogonal repumping laser beams have a dark-line volume in the longitudinal axis at their cross over. With a total trapping laser power of 40 mW and repumping laser power of 18 mW, we obtain an atomic OD up to 160 in an electromagnetically induced transparency (EIT) scheme, which corresponds to an atomic-density-length product NL = 2.05 × 10(15) m(-2). In a closed two-state system, the OD can become as large as more than 600. Our 2D MOT configuration allows full optical access of the atoms in its longitudinal direction without interfering with the trapping and repumping laser beams spatially. Moreover, the zero magnetic field along the longitudinal axis allows the cold atoms maintain a long ground-state coherence time without switching off the MOT magnetic field, which makes it possible to operate the MOT at a high repetition rate and a high duty cycle. Our 2D MOT is ideal for atomic-ensemble-based quantum optics applications, such as EIT, entangled photon pair generation, optical quantum memory, and quantum information processing.
We describe an apparatus where many species of ultracold atoms can be simultaneously trapped and overlapped with many species of ions in a Paul trap. Several design innovations are made to increase the versatility of the apparatus while keeping the size and cost reasonable. We demonstrate the operation of a three-dimensional (3D) magneto-optical trap (MOT) of 7Li using a single external cavity diode laser. The 7Li MOT is loaded from an atomic beam, with atoms slowed using a Zeeman slower designed to work simultaneously for Li and Sr. The operation of a 3D MOT of 133Cs, loaded from a 2D MOT, is demonstrated, and provisions for MOTs of Rb and K in the same vacuum manifold exist. We demonstrate the trapping of 7Li+ and 133Cs+ at different settings of the Paul trap and their detection using an integrated time-of-flight mass spectrometer. We present results on low energy neutral-neutral collisions (133Cs-133Cs, 7Li-7Li, and 133Cs-7Li collisions) and charge-neutral collisions (133Cs+-133Cs and 7Li+-7Li collisions). We show evidence of sympathetic cooling of 7Li+ (133Cs+) due to collisions with the ultracold 7Li (133Cs).
We present the simultaneous trapping and cooling of 85{}^{85}85Rb, 87{}^{87}87Rb and 133{}^{133}133Cs in a triple-species magneto-optical trap (MOT). This demonstration is obtained using an all-fibre compact and robust laser system based on telecom 1.5 μμμm and 2 μμμm technologies. We characterise the two-body interspecies losses in the double and triple-species MOT. We calculate the two-body interspecies trap-loss coefficient for the 85{}^{85}85Rb/133{}^{133}133Cs and the 87{}^{87}87Rb/133{}^{133}133Cs pairs, representing a variation of less than 7 \% in atom number. No losses are observed between 85{}^{85}85Rb and 87{}^{87}87Rb in our experimental conditions. We find that interspecies interactions inside the triple-species MOT do not prevent trapping and cooling 108^{8}8 atoms for each species, making our system suitable for future multi-species cold-atom interferometry applications.
This thesis presents progress toward the production of ultracold CsYb molecules. To this end, an apparatus capable of producing magneto optical traps of Yb and Cs was designed, built and tested. Both atoms are produced in a dual species oven and both slowed to low speeds by a single Zeeman slower. From the Zeeman slower atoms are captured in a dual-species magneto-optical trap. To cool caesium the 852 nm D2 transition is addressed by two lasers for cooling and repump. For ytterbium the 399 nm 1S0 ⇒ 1P1 transition is addressed for the Zeeman slower and the 556 nm 1S0 ⇒ 3P1 transition is addressed for the magneto-optical trap. The 399 nm light is produced by two homebuilt diode lasers in an injection-seeding setup, which can produce up to 100 mW. The 556 nm light is produced from a commercial frequency doubled fiber laser, which can produce up to 260 mW. The Zeeman slower is characterised experimentally for both Cs and Yb, and the results compared to those of a numerical simulation of the slower for Yb. The velocity distribution exiting the slower is very sensitive to the exact magnetic field profile, the laser power and detuning of the laser light. The number of atoms loaded into the magneto-optical trap was investigated as a function of the magnetic field gradient, the laser power and the laser detuning. The capture velocity of the Yb MOT is small because the linewidth of the MOT transition is narrow, and so we investigated the influence of broadening the laser linewidth by adding multiple finely-spaced sidebands to the laser light. After optimisation the caesium MOT trapped 5.5 ×10^8 atoms at 125 ± 4 μK. The ytterbium MOT trapped 4.7 ×10^9 atoms at 81 ± 2 μK. Lastly we demonstrate that both MOTs can be produced in the same vacuum chamber simultaneously.
This thesis reports on the realisation and characterisation of a magnetically trapped ultracold atomic mixture of 87Rb and 133Cs in the F = 1, mF = −1 and F = 3, mF = −3 hyperfine states respectively. A compact two-species double magneto-optical trapping (MOT) apparatus is constructed in which a pyramid MOT acts to provide an independent flux of both atomic species for capture in the ultra-high vacuum science region of the apparatus. For the two-species science MOT in which this atom flux is captured, interspecies light assisted inelastic collisions are found to be a highly significant loss mechanism. A novel optical pressure spatial displacement technique is developed to minimise such losses, allowing near independent simultaneous loading of up to ' 8 × 108 87Rb and ' 3 × 108 133Cs atoms into an Ioffe-Pritchard ‘baseball ’ magnetic trap at magnetic bias fields of 166.70(6) and 165.50(6) G respectively. At the loaded 87Rb and 133Cs atom number densities of 1.78(6) × 109 and