This thesis describes the design, construction and optimisation of two compact \nsetups to produce ⁸⁷Rb Bose-Einstein condensates and dual ⁷Li-⁸⁷Rb Magneto-Optical Traps (MOTs). The motivation for compact systems is to have simplified \nsystems to cool the atoms. The first experimental setup is based on a single pyrex \nglass cell without the need for atom chips. Fast evaporation will be achieved in a hybrid trap comprising of a magnetic quadrupole trap and an optical dipole trap \ncreated by a Nd:YVO4 laser and with future plans of using a Spatial Light Modulator \n(SLM). To enhance an efficient and rapid evaporation, we have investigated Light-Induced Atomic Desorption (LIAD) to modulate the Rb partial pressure during the cooling and trapping stage. With this technique, a ⁸⁷Rb MOT of 7 x 10⁷ atoms was loaded by shining violet light from a LED source into the glass cell, whose walls are coated with rubidium atoms. The atoms were then cooled by optical molasses and then loaded into a magnetic trap where lifetime measurements demonstrated that LIAD improves on magnetically-trapped atoms loaded from constant background pressure by a factor of six. This is quite encouraging and opens the possibility to do a rapid evaporation. In a second experiment, we have designed a compact system based on a stainless steel chamber to trap either ⁷Li or ⁶Li atoms in a MOT loaded from alkali-metal dispensers without the need of conventional oven-Zeeman slower. This setup can also load ⁸⁷Rb atoms, allowing future projects to simultaneously produce degenerate quantum gases of bosonic ⁸⁷Rb and fermionic ⁶Li atoms.
This thesis describes the design, construction and optimisation of two compact \nsetups to produce ⁸⁷Rb Bose-Einstein condensates and dual ⁷Li-⁸⁷Rb Magneto-Optical Traps (MOTs). The motivation for compact systems is to have simplified \nsystems to cool the atoms. The first experimental setup is based on a single pyrex \nglass cell without the need for atom chips. Fast evaporation will be achieved in a hybrid trap comprising of a magnetic quadrupole trap and an optical dipole trap \ncreated by a Nd:YVO4 laser and with future plans of using a Spatial Light Modulator \n(SLM). To enhance an efficient and rapid evaporation, we have investigated Light-Induced Atomic Desorption (LIAD) to modulate the Rb partial pressure during the cooling and trapping stage. With this technique, a ⁸⁷Rb MOT of 7 x 10⁷ atoms was loaded by shining violet light from a LED source into the glass cell, whose walls are coated with rubidium atoms. The atoms were then cooled by optical molasses and then loaded into a magnetic trap where lifetime measurements demonstrated that LIAD improves on magnetically-trapped atoms loaded from constant background pressure by a factor of six. This is quite encouraging and opens the possibility to do a rapid evaporation. In a second experiment, we have designed a compact system based on a stainless steel chamber to trap either ⁷Li or ⁶Li atoms in a MOT loaded from alkali-metal dispensers without the need of conventional oven-Zeeman slower. This setup can also load ⁸⁷Rb atoms, allowing future projects to simultaneously produce degenerate quantum gases of bosonic ⁸⁷Rb and fermionic ⁶Li atoms.
This Thesis contains details of the construction and characterisation of a compact apparatus for the cooling of ultracold atoms to quantum degeneracy, and their manipulation in flexible holographic optical traps. We have designed and built two iterations of this apparatus. The first version consists of a stainless steel single-cell vacuum chamber, in which we confine ⁸⁷Rb and ⁶Li or ⁷Li in a Magneto-Optical Trap. We characterise the alternative methods of pulsed atomic dispenser and Light Induced Atomic Desorption (LIAD) to rapidly vary the background pressure in the vacuum chamber with the view to enabling efficient evaporative cooling in the single chamber, loading MOTs of up to 10⁸ atoms using pulsed dispensers. The LIAD is found to be ineffective in loading large MOTs in this setup, while the pulsed dispensers method gradually increases the background pressure in the chamber over time. \nBased on the results of this first iteration, we designed and built a second single-chamber apparatus for cooling of ⁸⁷Rb to quantum degeneracy. The LIAD technique was used to successfully load MOTs containing 8x10⁷ atoms in this single pyrex cell with a rapidly-varying background pressure. The lifetime of an atomic cloud loaded from the MOT into a magnetic trap increased by a factor of 6 when LIAD was used. \nThe holographic optical traps for cold atoms are generated using a Spatial Light Modulator, and we present our novel method for improving the quality of holographic light patterns to the point where they are suitable for trapping ultracold atoms using a feedback algorithm. As demonstrations of this new capability, we show power-law optical traps which provide an efficient, reversible route to Bose-Einstein Condensation and a dynamic ring trap for the investigation of superfluidity in cold atoms.
This thesis describes the progress achieved towards two goals. One is the construction of a compact magneto-optical trap (MOT) apparatus, used both as a standalone undergraduate laboratory experiment and as part of a public engagement demonstration of cold atom physics. The setup, which utilises a dichroic atomic vapour laser lock (DAVLL) system plus homemade sideband generation electronics, is capable of trapping and cooling up to 8x10⁷ ⁸⁵Rb atoms in a standard six-beam laser cooling scheme. The second goal is the loading of an ultracold ensemble of ⁸⁷Rb atoms into novel optical trap geometries using a phase-only liquid crystal spatial light modulator (LC SLM) for applications to atomtronics and quantum simulation. Details of a double vacuum chamber apparatus, designed to produce the first Bose-Einstein condensates (BECs) at St Andrews, are provided. The setup incorporates a hybrid trap evaporative cooling scheme towards quantum degeneracy and reliably produces BECs of 1.9 10⁵ ⁸⁷Rb atoms. Two computational techniques, developed during the course of this project, are presented with the aim of creating flexible, smooth holographic optical traps. The first method illuminates a single SLM with overlapped, co-propagating light beams of different wavelengths to create a composite optical pattern for atom manipulation. The second uses conjugate gradient minimisation to create exceptionally high fidelity light patterns in both amplitude and phase for light in the output plane. These techniques, combined with the implementation of a light sheet into the experimental setup, are used to trap atoms in both a ring profile and in a set of narrow waveguides connected with a tunnelling barrier.
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.
The possibility to mould and control pure quantum systems has been offered by the experimental observation of Bose-Einstein condensation, a unique phase of matter when macroscopic quantities of a gas occupy the lowest quantum state. Techniques for creating these degenerate gases vary from laboratory to laboratory; each offers an unique test bed for studying quantum physics on a macroscopic scale. This thesis reports on the experimental design, construction and performance of an apparatus to create two-component 87Rb and 41K condensates for studies of non-equilibrium dynamics. This thesis is broken down as follows. In Chapter 1, a brief overview of the history and status of Bose Einstein condensates is presented, to affirm the motivation behind our work. Chapter 2 then presents the fundamental theory and background information to understand how and why our experiment was built. Chapter 3 describes the bulk of the work undertaken at the beginning of this thesis. In particular it describes the design choices, construction and performance of the vacuum, and laser and magnetic coil systems that are the key structural elements of the apparatus. In particular the vacuum system is a two-component differentially pumped system designed to optimise the number and lifetime of trapped atoms. Another integral element of the vacuum chamber is the science cell that enables high optical access, and close physical, access to an atomic cloud. As a result, high resolution imaging, ≃ 980 nm resolution at 780 nm is expected with a commercial microscope objective lens. The laser system is carefully de- signed to best combine and deliver the seven different optical frequencies required to simultaneously trap and manipulate 87Rb and 41K atoms. The magnetic coil system also represents an integral component of the apparatus, responsible for trapping and transferring atoms in a quadrupole field. One pair of coils is able to have their current direction reversed in order to generate bias fields. This allows access to Feshbach resonances between the two species, once they have been condensed. The second part of this thesis, Chapter 4, describes the performance of the apparatus when used to simultaneously trap 41K and 87Rb in the 3D magneto- optical trap (MOT) and produce a condensate of 87Rb atoms. In particular 1 × 109 rubidium atoms are routinely trapped in the 3D-MOT and transferred to the science chamber. In the hybrid trap the atoms are evaporatively cooled via microwave radiation, later to be used to sympathetically cool 41K, and loaded into a hybrid optical dipole and magnetic trap. At this stage ≃ 5 × 106 atoms are evaporatively cooled, by lowering the trap depth of the optical dipole beam, until a condensate of 87Rb is formed, containing 1.5 × 105 atoms. Additionally we are able to produce 3D MOTs of 41K simultaneously with the 87Rb 3D MOTs.
This thesis describes the design, construction and optimisation of a new apparatus to produce Bose-Einstein condensates (BECs) of 87Rb atoms. The main aim in building this system was to include a high resolution imaging system capable of resolving single atoms. Optical access for the imaging system was created by including a stage of atom transport in which the atoms are magnetically transferred ~50 cm from a magneto-optical trap (MOT), where they are initially collected, to a glass science cell where experiments are carried out and imaging takes place. Two magnetic transport schemes have been demonstrated, based on approaches first used in other laboratories. First, a scheme in which the atoms are transferred in a moving pair of magnetic trapping coils. Second, a hybrid scheme where the atoms are translated part of the distance in the moving coils, and the rest of the way by switching the current in a chain of fixed coils. This second scheme was designed to allow optical access for a high numerical aperture microscope objective to be placed immediately next to the science cell for high resolution imaging.The atoms were first collected in a large pyramid MOT which can be loaded with 3 × 10^9 atoms in a time of 20 s. Around half of these atoms – those in the |F = 1, mF = −1> magnetic substate – were then magnetically trapped prior to transport. The typical fraction of the trapped atoms transferred to the science cell was ~30% and ~18% for the moving coils and hybrid schemes respectively.Evaporative cooling was carried out on the atom cloud following transport with the moving coils and loading into a time-orbiting potential trap. The optimised cooling sequence lasted for 28 s and consistently produced a pure condensate with 5 × 10^5 atoms. A BEC has also been produced by evaporative cooling following hybrid transport. The next experimental steps will be to optimise the hybrid transfer approach further and install the high resolution imaging system.The system is well-placed to continue an ongoing series of experiments in which ultracold atoms are trapped in RF-dressed potentials. These potentials will be used to study low-dimensional quantum gases as well as in experiments where small atom number BECs are rapidly rotated to enter the fractional quantum Hall regime.
This thesis describes a new apparatus designed to study ultracold gases of rubidium. The apparatus comprises a six-beam MOT chamber and a dierential pumping stage leading into a 'science chamber'. This science chamber is constructed from a rectangular glass cell. Atomic gases of rubidium are collected in a MOT and then transferred into a magnetic quadrupole trap. This quadrupole trap is mounted on a motorised translation stage. This setup transports the atoms into the science chamber, where they are transferred into a static quadrupole trap which is built around the glass cell. During the transport the atoms are deected over a glass prism, which shields the science chamber from stray rubidium from the MOT chamber. The magnetic transport is studied in detail and the deection over the glass prism is fully described simulating the displacement of the quadrupole trap. Using the magnetic quadrupole trap in the science chamber to store one rubidium isotope, we are able to load the other rubidium isotope in the MOT chamber and transfer it also into the science chamber. There, the two magnetic traps are merged and variable ratios of isotopic mixtures can be created. The merging of the two quadrupole traps could be employed in future experiments to cool 85Rb sympathetically with 87Rb. In the science chamber forced radio-frequency evaporation is performed and the loading of a far-detuned dipole trap is studied. Initially the dipole trap is realised as a hybrid trap, a single beam dipole trap in combination with the quadrupole trap. Further studies include the loading of a crossed beam dipole trap. We demonstrate that the apparatus is capable of producing 87Rb condensates. Preliminary studies of 85Rb in the dipole trap are included which hopefully in future will lead to a quantum degenerate gas of 85Rb.