This paper proposes a dual-color grating chip design method for simultaneously capturing dual atomic clouds (87Rb and 133Cs). By simulating key parameters such as the grating period, etching depth, duty cycle, coating material, and thickness, the optimal design parameters were determined to ensure efficient dual-wavelength diffraction and maximize the number of captured atoms. Experimental results demonstrate the simultaneous trapping of 1.6E8 87Rb atoms and 7.8E6 133Cs atoms, thereby offering an approach for multi-species cold atom systems. This dual-species grating magneto-optical trap (GMOT) system has potential applications in precision measurements such as cold atom clocks, quantum interferometers, and quantum electrometry.
This thesis presents the optimization and characterization of a magneto-optical trap (MOT) setup for rubidium-87 atoms. The apparatus is designed to provide a source of cold atoms, with temperatures around 100
μK, near the tip of a hollow-core photonic crystal fiber. The ultimate goal is to load the cold atomic cloud into the fiber to explore the unique properties of this hybrid system. Since the number of captured atoms depends on the interplay between the magnetic field and detuning, a detailed study was conducted to investigate the number of trapped atoms as a function of different detuning values and magnetic field gradients. By comparing two measurement methods, it was determined that the MOT is capable of trapping approximately
107 rubidium atoms. The optimal magnetic field gradient and laser detuning frequency were found to be
B′=9.32G/cm and
δ≈−13 MHz, respectively. Additionally, the number of captured atoms was found to be strongly dependent on the background pressure inside the MOT chamber. In this regard, it was observed that by closing the rubidium source valve, the pressure can be reduced by up to 80\% over a 24-hour period, and one possible way to measure it could be through the background signal with the magnetic field gradient turned off. Then we analyzed the trap lifetime
τ, which is also inversely proportional to the partial pressure of rubidium. Under optimal conditions, we obtained a trap lifetime of
0.31s. Furthermore, a temperature estimation of the atomic cloud was performed using the time-of-flight (TOF) method. The velocity distribution along the
x-axis, which lie in the imaging plane, was captured with a CMOS camera and yielded temperature of
Tx=(252±20)μK. These results provide essential insights into the optimization of the MOT parameters and lay the foundation for future studies involving the loading of cold atoms into hollow-core photonic crystal fibers.
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.
Our study indicates that the number of trapped Rb atoms in a magneto-optical trap (MOT) strongly depends on the trapping laser intensity and detuning, the repumping laser intensity and the magnetic gradient. We estimate the trapped-atom numbers changing with the trapping laser intensity and detuning, using a two-level system model. The theoretical results are in qualitative agreement with the experimental results. The experimental results also show an obvious dependence of the trapped-atom numbers on repumping laser intensity and the magnetic gradient, which the simple theory cannot account for. These studies are helpful for selecting suitable experimental parameters to achieve larger numbers of cold atoms.
We present the simultaneous trapping and cooling of
85Rb,
87Rb and
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
μm and 2
μm 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
85Rb/
133Cs and the
87Rb/
133Cs pairs, representing a variation of less than 7 \% in atom number. No losses are observed between
85Rb and
87Rb in our experimental conditions. We find that interspecies interactions inside the triple-species MOT do not prevent trapping and cooling 10
8 atoms for each species, making our system suitable for future multi-species cold-atom interferometry applications.
We present a magnetic trap for cold atoms near a surface of a millimeter-sized atom chip. The trap allows us to capture a large number of atoms with modest electrical currents (40 A) and to generate large magnetic gradients (>300 G cm−1). Here we report a mixture containing 6 × 109 atoms for the two rubidium isotopes 87Rb and 85Rb. This device does not require cleanroom facilities nor micro-machining technologies which makes its construction easier. In addition our design allows the implementation of an optical dipole trap with a laser beam passing through the chip.