摘要
对真空腔内的冷原子进行高分辨成像通常需要原子与像平面之间保持较大的距离,这不利于成像系统在光学元件密集的冷原子实验中实现.设计了一套显著降低原子与像平面距离的高分辨成像系统,实现了1μm的分辨率与 50倍的放大率.仿真结果表明,通过改变透镜间距,可以适应 0-15 mm厚度范围的真空窗口.该成像系统由数值孔径为 0.47的显微物镜和有效焦距为 1826 mm的远摄物镜组合而成.结合成像波长为 470-1064 nm的仿真结果,该系统可以对钠、锂、铯等不同种类的原子进行高分辨成像.
Abstract
In cold atom experiments,high resolution imaging systems have been used to extract in-situ density information when studying quantum gases,which is one of the hot topics in this field.Such a system is usually called"quantum-gas microscope".In order to achieve a long working distance and large magnification,high resolution imaging of cold atoms through a vacuum window usually requires a long distance between the atoms and the camera.However,due to space limitation caused by a large number of nearby optical elements,it may be difficult to realize a long imaging system,which is a common case in cold atom experiments.Herein we present an imaging system that can achieve a short distance between the atoms and the image plane with diffraction-limited 1 μm resolution and 50 magnification.The telephoto lens design is adopted to reduce the back focal length and enhance the pointing stability of the imaging lens.The system is optimized at an operating wavelength of 767 nm and corrects aberrations induced by a 5-mm-thick silica vacuum window.At a working distance of 32 mm,a diffraction-limited field of view of 408 μm is obtained.The simulation result shows that by changing the air space between lenses,our design operates across a wide range of window thicknesses(0-15 mm),which makes it robust enough to be used in typical laboratories.This compact imaging system is made from commercial on-shelf Φ2 in(1 in = 2.54 cm)singlets and consists of two components:a microscope objective with a numerical aperture of 0.47 and a telephoto objective with a long effective focal length of 1826 mm.Both are infinitely corrected,allowing the distance between them to be adjusted to insert optical elements for irradiating atoms with laser beams of different wavelengths without affecting the imaging resolution.Taking the manufacturing and assembling tolerances into consideration,the Monte Carlo analyses show that more than 95%of the random samples are diffraction-limited within the field of view.This high success rate ensures that these two objectives can be achieved easily in the experiment.Combined with its performance with other wavelengths(470-1064 nm),this imaging system can be used for imaging different atom species,such as sodium,lithium,and cesium.
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