Bài báo khoa học

A microscope objective used for optical tweezers must have a numerical aperture larger unity (NA>1). Because the numerical aperture can never be greater than unity for an objective lens in air, then the resolving power is limited. Since the microscope objective must be glued to an immersion oil having refractive index higher than that of air. The NA of the microscope objective depends on the thickness and refractive index of the immersion oil. In this paper, a MO using a thin layer of negative or positive nonlinear organic dye replacing the conventional immersion oil to enhance NA is proposed. The explicit expressions of the NA, focal shift, and optical trap efficiency depending on the nonlinear refractive index and thickness of the thin layer are theoretically derived using the raytransfer matrix. The optical properties of “called” nonlinear microscope objective are numerically observed based on the experimental parameters. The obtained results show that the nonlinear microscope objective is considerably improved for nonlinear optical tweezers