An adaptable two-lens high-resolution objective for single-site resolved imaging of atoms in optical lattices

In this paper, we present a high-resolution, simple, and versatile imaging system for single-site resolved imaging of atoms in optical lattices. The system, which relies on an adaptable infinite conjugate two-lens design, has a numerical aperture of 0.52, which can in the ideal case be further extended to 0.57. It is optimized for imaging on the sodium D₂-line but allows us to tune the objective's diffraction limited performance between 400 nm and 1000 nm by changing the distance between the two lenses. Furthermore, the objective is designed to be integrated into a typical atomic physics vacuum apparatus where the operating distance can be large (>20 mm) and diffraction limited performance still needs to be achieved when imaging through thick vacuum windows (6 mm to 10 mm). Imaging gold nanoparticles, using a wavelength of 589 nm which corresponds to the D₂-line of sodium atoms, we measure diffraction limited performance and a resolution corresponding to an Airy radius of less than 0.7 µm, enabling potential single-site resolution in the commonly used 532 nm optical lattice spacing.