In this report I attempt to outline the process of developing and building an absorption imaging system capable of imaging ultracold atoms. In the theory section I will discuss the elements required to estimate the atom number and derive the equations required to determine the temperature of the atom cloud. I will outline the general features of a microscopic - two lens imaging setup via the principles of geometric optics. A discussion of optical design process and its features will be carried out with an example on absorption imaging. The essence of basic optical design process will be given.
In this report I attempt to outline the process of developing and building an absorption imaging system capable of imaging ultracold atoms. In the theory section I will discuss the elements required to estimate the atom number and derive the equations required to determine the temperature of the atom cloud. I will outline the general features of a microscopic - two lens imaging setup via the principles of geometric optics. A discussion of optical design process and its features will be carried out with an example on absorption imaging. The essence of basic optical design process will be given.
Optical imaging plays a central role in ultracold atom experiments by enabling quantitative measurements of atomic density, temperature, atom number, and condensate dynamics. Achieving high-fidelity absorption imaging requires a well-characterized optical system with accurately calibrated magnification and spatial resolution. In this work, I designed, implemented, and experimentally characterized a dual-view optical imaging platform for future absorption imaging of ultracold sodium atoms. The system consists of two independent three-lens relay imaging systems providing top and side views of the atomic sample. Two low-magnification configurations with nominal magnification 0.6 were developed for imaging the relatively large sodium magneto-optical trap (MOT), while higher-magnification configurations with nominal magnifications of 4 and 10 were designed for Bose–Einstein condensate (BEC) imaging. The work included the integration and optimization of the laser cooling and trapping apparatus, improvements to the magnetic-field control system, and the alignment and calibration of both imaging paths. Characterization using a laser and a USAF 1951 resolution target yielded measured magnifications of 0.653 ± 0.033 and 0.521 ± 0.016 for the side and top MOT imaging systems, with corresponding spatial resolutions of 13.92 µm and 9.84 µm. The BEC imaging systems achieved measured magnifications of 4.094 ± 0.060 (top) and 10.817 ± 0.172 (side), with spatial resolutions of 9.84 µm and 6.20 µm, respectively. These measurements agree well with the theoretical diffraction-limited resolutions of 7.19 µm for the 0.6 and 4 magnification systems and 2.87 µm for the 10 magnification system, with the remaining differences attributed primarily to practical optical aberrations and alignment tolerances. The calibrated dual-view imaging platform provides the spatial resolution and quantitative accuracy required for absorption imaging of ultracold sodium atoms and establishes the experimental foundation for future investigations of sodium magneto-optical traps, Bose–Einstein condensation, and coherent spin dynamics in spinor sodium gases.
Engineered ultracold atomic systems are a valuable platform for fundamental quantum mechanics studies and the development of quantum technologies. At near zero absolute temperature, atoms exhibit macroscopic phase coherence and collective quantum behavior, enabling their use in precision metrology, quantum simulation, and even information processing. This review provides an introductory overview of the key techniques used to trap, manipulate, and detect ultracold atoms, while highlighting the main applications of each method. We outline the principles of laser cooling, magnetic and optical trapping, and the most widely used techniques, including optical lattices and tweezers. Next, we discuss the manipulation methods of atomic internal and external degrees of freedom, and we present atom interferometry techniques and how to leverage and control interatomic interactions. Next, we review common ensemble detection strategies, including absorption and fluorescence imaging, state-selective readout, correlation and quantum non-demolition measurements and conclude with high-resolution approaches. This review aims to provide newcomers to the field with a broad understanding of the experimental toolkit that underpins research in ultracold atom physics and its applications across quantum science and technology.
We report on a far above saturation absorption imaging technique to investigate the characteristics of dense packets of ultracold atoms. The transparency of the cloud is controlled by the incident light intensity as a result of the nonlinear response of the atoms to the probe beam. We detail our experimental procedure to calibrate the imaging system for reliable quantitative measurements and demonstrate the use of this technique to extract the profile and its spatial extent of an optically thick atomic cloud.
In this project, I investigated a new imaging technique for cold and ultra-cold atoms based on the four-wave mixing (FWM) process. In theory, this technique will provide more precise measurements of the number and spatial density distribution of cold atoms than fluorescence or absorption imaging. Since FWM is usually studied in high optical depth vapor cells but cold atoms have low optical depths, I first studied the dependence of FWM on optical depth. Results showed that Stokes field emission due to FWM decreases exponentially with decreasing optical depth, and that it can still be observed at optical depths of approximately 1. After determining the optimal conditions for Stokes field emission, I tried observing FWM with cold atoms. Absorption and emission-like features were observed on the probe and Stokes fields which depended on the interaction of the control field, the probe field, and the trapped atoms. There is significant reason to believe that these features are associated with the FWM process, although further studies need to be undertaken to determine more definitively the nature of these features, how they depend on various parameters of the experimental setup, and how they may be related to the number and density of the cold atoms.
At temperatures near absolute zero, bosons form a macroscopic quantum state that can be manipulated and imaged in a very controlled and tunable way. To reach these extreme temperatures near absolute zero, advanced methods in cooling, including laser and evaporative cooling, must be used. In addition to these techniques for cooling, atoms must also be held up against the constant pull of gravity, so additional trapping techniques using lasers and magnets are used. In our lab at University of San Diego, we are implementing a tunable lens system (TLS) to optically transfer atoms to a more optically accessible location. A tunable lens (TL) is a lens where the curvature of the lens can be adjusted through an applied electrical current, thus translating where the focus of a lens is in a controlled way. This research aims to discover the optimal setup for a TLS to be used in the transportation of ultracold atoms in our system. In this research, I will report on the building of the TLS within the lab and the adjustment of various systems pertaining to the TL.
Abstract The accurate determination of atom numbers is an ubiquitous problem in the field of ultracold atoms. For modest atom numbers, absolute calibration techniques are available, however, for large numbers and high densities, the available techniques neglect many-body scattering processes. Here, a spatial calibration technique for time-of-flight absorption images of ultracold atomic clouds is presented. The calibration is obtained from radially averaged absorption images and we provide a practical guide to the calibration process. It is shown that the calibration coefficient scales linearly with optical density and depends on the absorbed photon number for the experimental conditions explored here. This allows for the direct inclusion of a spatially dependent calibration in the image analysis. For typical ultracold atom clouds the spatial calibration technique leads to corrections in the detected atom number up to ≈ 12 % and temperature up to ≈ 14 % in comparison to previous calibration techniques. The technique presented here addresses a major difficulty in absorption imaging of ultracold atomic clouds and prompts further theoretical work to understand the scattering processes in ultracold dense clouds of atoms for accurate atom number calibration.