Theoretical Study Of Atomic And Molecular Surface Photo-confinement Based On Subwavelength Grating Structures

High contrast subwavelength grating (HCGs) have many unique properties, such as low loss, high reflectivity, bandwidth adjustable, simple structure as well as phase matching and strong focusing ability. They can be fabricated with the micro/nano manufacturing technology and they have broad application prospects in the field of quantum optics.In this paper, we first propose a novel scheme of a concave grating reflector as an optical dipole trap for trapping atoms. A reflector of one-dimension flat grating structure designed shows high reflectivity and wide wavelength-tuning bandwidth. Then it is extended to two-dimension grating structure, in addition to having the above optical features, the structure exhibits great focusing ability. Especially, the light intensity at the focal point is about 100 times higher than that of the incident light. As a result, such strong focusing optical field reflected from the curved grating structure can be enough to provide the deep potential to trap cold atoms. We discuss the feasibility on the 2D concave grating structure as an optical dipole trap from the following aspects:(1) Van der Waals potential to the surface has alow effect on trapped neutral atoms. (2) The maximum trapping potential 1.14 mK for cold 87Rb atoms, which is high enough to trap cold atoms from a standard Rb magneto-optical trap with a temperature of 120μK, and the maximum photon scattering rate of Rb atoms in the optical trap is lower than 1/s. (3) Microtrap array on a dielectric chip that can manipulate and control cold molecules and microscopy particles.Next, we propose an optical cavity composed of two identical high-contrast subwavelength flat grating structures. And we simulate the distribution of the optical field with finite element software and the result shows that when abeam of light of the incident wavelength of 1064nm enters the bottom of the cavity, a coherent standing wave field will be formed in the cavity, if a molecule enters the standing wave field, it will suffer from an optical dipole force and its trajectory will be changed, therefore the optical field can be used for molecular deposition Then we use the monte carlo method to simulate molecular deposition and the result shows that most of the molecules are deposited in the region of the largest light intensity, and the pattern of molecular deposition is nearly the same as the distribution of optical field.