Isotropic laser cooling is regarded as one of the crucial laser cooling techniques because of its distinctive benefits including simplicity, compactness, and robustness. It has been extensively applied in areas including atomic microwave clocks, quantum simulation, and quantum sensing. As a distinct distribution type of cold atoms in isotropic laser cooling, cold atoms with quasi-two-dimensional distributions have significant applications and usefulness in fields of study, including atomic cooling and quantum precision measurement. Isotropic laser cooling does not restrict atoms, different from techniques like magneto-optical traps. The distributions of the optical field and the cold atoms inside the cavity are significantly influenced by the laser injection methodology and cavity design. To obtain cold atoms with a quasi-two-dimensional distribution, one must effectively establish a uniformly distributed quasi-two-dimensional optical field in a flat cavity. In order to get a uniform optical field, we explore the impact of various incident optical field parameters on the optical field distribution using optical simulations to study how to produce a quasi-two-dimensional optical field distribution.

The main method for creating a nearly two-dimensional optical field in a flat cavity is the subject of this study. We propose a flat diffusion cavity-based cavity structure for the first time. It models the effects of two alternative injection techniques, namely free-space injection and optical fiber injection, on the optical field distribution using optical simulation software. Using the optical fiber injection technique as a foundation, we explore how changing the angle of injection affects the way the light field is distributed inside the cavity. We also investigate the distribution of the optical field inside the cavity as a function of important optical fiber characteristics, particularly the numerical aperture and core diameter. Finally, we investigate the relationship between differences in the optical field distribution inside the cavity and variations in cavity diameters, and this demonstrates that by adjusting these factors, we may significantly improve the optical field's homogeneity.

The simulation results show that the optical fiber injection method is superior to the free-space optical injection strategy in producing a homogeneous optical field within the flat diffuse-reflectance cavity (Fig. 4). Furthermore, by modifying particular parameters, the optical field may be optimized. The homogeneity of the optical field is improved to some extent when the angle of incidence of the optical fiber rotates within reasonable bounds. To keep a uniform optical field distribution, it is crucial to prevent large angle variations (Fig. 5). While changes in core diameter have relatively little influence on the optical field distribution, variations in numerical aperture have a large impact on the uniformity of the optical field (Fig. 6). As a result, choosing an optical fiber with the right specifications is essential for improving the homogeneity of the optical field. Due to structural modifications, increasing the cavity height while keeping the proper height enhances the optical field dispersion. Sometimes, it even improves the optical power density at particular locations. The optical power density distribution within the cavity, however, shows a declining tendency with an overall rise in height (Fig. 7). With a rising side length scaling factor, the optical power density inside the cavity displays a negative power-law relationship decrease pattern. The power consumption for the incident cooling light therefore grows dramatically as the cavity volume expands, even with the same optical power density requirements (Fig. 8).

Establishing a uniform optical power density distribution is a difficult point in studies designed to achieve a quasi-two-dimensional distribution of cold atoms within a flat diffuse-reflectance cavity. We simulate several cooling light injection strategies. When optical fiber injection is utilized instead of free-space optical injection, the optical field distribution is more uniform. The flatness of the optical field can be optimized within particular locations by adjusting the angle of incidence of the optical cable. The optical field's homogeneity is also strongly impacted by the optical fiber's numerical aperture. The initial beam diameter and divergence angle of the incident light are both determined by the numerical aperture and core diameter of the optical fiber. The flatness of the optical field can be improved within certain geographic areas by using optical fibers with the right characteristics. The optical power density inside the cavity shows a negative exponential drop trend as the cavity volume grows. These simulation findings offer helpful pointers for attaining a very homogeneous and quasi-two-dimensional optical field distribution. They also clarify the connection between variations in cavity size and the optical field distribution in the context of isotropic laser cooling.