A magneto-optical trap (MOT) for rubidium (Rb) atoms has been in operation at the University of San Carlos Optoelectronics Research Laboratory in Cebu City since 1998. The experimental design for this MOT is based on the system described by Wieman et al. (1995). This system formed the backbone of the research which resulted in the first observation of Bose-Einstein condensation (BEC) by the same group in 1995. An essential step for realizing this remarkable result was the accuracy in the timing mechanism of the experiment. To obtain an MOT in which we can switch the laser and magnetic fields with sub-millisecond accuracy, we have put considerable efforts to realize a computer-controlled system.
Previous measurements have been used to validate our new results. The realization of a fast switch for the trapping laser creates the opportunity to measure time-of-flight (TOF) signals. These ballistic measurements can be used to infer the temperature of the cloud of trapped atoms.
We hope to continue working on this automated system of the MOT towards BEC as a long-term goal of our research group.
Laser cooling experiments are a good example of how the interaction between light and matter can be applied to manipulate neutral atoms. At the University of San Carlos we have constructed a magneto-optical trap (MOT) for rubidium (Rb) atoms. The setup is based on the design of the MOT Wieman et al used in their efforts to reach Bose-Einstein condensation. The use of diode lasers enables the introduction of these advanced experiments at undergraduate level. Since 1998, when the MOT became operational at USC, a great number of undergraduate students have done the experiment. Not only did they learn the basics of cooling and trapping, they also gained experience in operating lasers properly, vacuum technology, and techniques for frequency stabilization. In some cases students opted to perform spectroscopy experiments on Rb atoms, which could easily be done using this setup. Of course, the presence of the MOT also gave a great boost to the research in optoelectronics, a new research direction in our department. Characterizing the MOT has resulted in several scientific papers in local physics journals as well as presentations to the annual Philippine Physics Congress. The next step is towards the realization of Bose-Einstein condensation of Rb in our Optoelectronics Laboratory.
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.
This research was focused on the construction of a magneto-optical trap (MOT) to create a Bose-Einstein Condensate (BEC) of 87Rb. The BEC is the coldest of the five states of matter functioning at a minuscule temperature of nanokelvin. A BEC is as close as we can get to absolute zero. Thus making it a valuable tool for researching the fundamental physics of quantum systems. Our setup utilizes both a high pressure and low-pressure MOT. The high-pressure MOT initiates the process with a high vapor density allowing for better Rb collection. The trapped atoms are then transported to the low-pressure MOT where there are no other atoms. Rb atoms are further cooled to a Bose-Einstein condensate temperature and are moved with more current-carrying coils to the glass BEC chamber. In the BEC chamber all Rb atoms are identical at their lowest quantum state. Although the process can be phrased in a few short sentences the setup and characterization of the entire system takes months to years of construction. # 43- 46 Environmental Fellows Program: Student Practicums
Since the first experimental demonstration of Bose-Einstein condensation (BEC) in an alkali-metal vapor, this subject has been attracting remarkable interests in the physics society. Hundreds of theoretical works concerning this subject have been reported so far. However, the number of reports about BEC experiments is much less than that of the theoretical works. This is because only a few experimental groups have succeeded in realizing BEC due to the experimental complexity and difficulties. The first step to create BEC in alkali-metal vapor is to collect a large number of atoms (/spl sim/-10/sup 9/) in an ultrahigh vacuum (/spl sim/10/sup 11/ torr). Recently, a double magneto-optical trap (MOT) system has been utilized for the first step. In this system, the atoms are first captured in a MOT from a vapor, and then transferred through a thin tube to the second MOT in an ultrahigh vacuum. To transfer the atoms, a pushing beam and a magnetic field are usually required to guide the atoms along the transfer tube. In the paper we report a simple double MOT system which uses neither a push beam nor a magnetic field to transfer the atoms. The atoms are transferred just by gravity. We can collect up to 2 x 10/sup 9/ rubidium atoms in the ultrahigh-vacuum MOT with this system and can achieve the BEC.
This thesis reports on the generation of MOT for laser cooling and trapping of Rubidium 87 atoms. Probe-pump technique have been used in Rb gas cell and doppler free absorption peaks has been observed. Peak at the crossover frequency will be locked for laser cooling and repump beams. This locked freuqency used in MOT to trap Rb atoms. The technique of optical molasses is used to cool the atoms and quadrupole magnetic field applied to confine or trap atoms at the center of MOT. Two chambers are constructed for 2D and 3D MOT with different pressure. Rb atoms loaded efficiently from the high flux cold atom beam generated in a compact 2D MOT. This is the first step of Bose Einstein Condensate (BEC). A performance of 2D MOT was tested by another main chamber of 3D MOT contains 3 pairs of counter-propagating beams. Over 5x10⁶ atoms trapped in a 3D MOT with loading rate of 1:8x10⁶ atoms/sec. This experiment provided an excellent starting point for future experiment on Rydberg atoms in dense ultracold quantum gases.
This works presents the design, experimental implementation, and characterization of a compact 2D Magneto-Optical Trap (MOT) as a source of cold rubidium-87 atoms at the Quantum Technologies Laboratory in Cinvestav Queretaro. In a small volume vacuum chamber, the setup uses rubidium dispensers near to the trapping region of the 2D MOT and operates at low pressures in the 10-8torr range. The main idea of the 2D MOT is to use it as an atomic compact source for future experiments, such as the demonstration of Bose-Einstein Condensation, quantum simulation, spinor condensates and topological materials, quantum memories, etc.