Electrostatic curved mirror of cold molecules
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摘要: 分子(原子)平面反射镜作为重要的光学元件之一, 被广泛应用于分子(原子)囚禁、储存、导引等实验中; 但由于其仅能实现粒子纵向速度改变而在横向上没有聚焦作用, 从而导致了粒子容易发散. 以重氨(ND3)分子为例, 提出了一种结构简洁、紧凑的微型静电曲面反射镜, 通过理论计算并与Monte-Carlo模拟, 验证了其在改变分子运动方向的同时能够实现横向聚束, 进而大大增加反射分子数目. 因此, 该类反射镜可广泛用于分子操控与装载以及构成各类分子腔体等领域.Abstract: As one of the most important optical instruments, molecular (atomic) reflecting mirrors have been broadly applied in experiments for trapping, loading, and guiding of molecules (atoms); however, given that the mirrors can only change the velocity of particles in the longitudinal direction, there is no focusing capability in the lateral direction and particles can subsequently diverge. Using ND3 as an example, we propose a compact micro electrostatic curved mirror to address this issue; we show via theoretical calculations and Monte-Carlo simulations that the proposed mirror can both direct a beam of molecules and achieve transverse bunching of molecules. This kind of reflecting mirror can be used in an extensive range of optical applications for manipulating or loading molecules, composing molecular cavities, and so forth.
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Key words:
- micro electrostatic curved mirror /
- cold molecules /
- molecular cavity
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图 1 (a)环形平面电极结构图, 电极宽度是200 μm, 间隔是300 μm, 中心电极半径是100 μm, 分子前进方向为 z 轴方向; (b)曲面电极结构图, 电极宽度与间隔和平面相同, 曲面的曲率半径R = 70 mm, 曲面高度340 μm
Fig. 1 (a) Illustrative structure of circular planar electrodes, with an electrode width of 200 μm, electrode spacing of 300 μm, and electrode radius of 100 μm. The forward direction of molecules is along the z-axis; (b) Illustrative structure of curved electrodes, whose electrode width and spacing are the same as the planar ones. The radius of curvature for this mirror is 70 mm, while its height is 340 μm
图 2 曲线表示反弹回来的ND3分子随时间变化的趋势图: 黑色曲线是分子在环形静电平面反射镜中的时间飞行(TOF)信号, 红色曲线则是分子在环形静电曲面反射镜中的TOF信号； 右上角曲线表示曲平面重力腔自由落体反射峰相对强度之比
Fig. 2 Dependence of density of ND3 molecules on time: The black curve denotes the time-of-flight (TOF) signal of the molecules on the circular electrostatic planar mirror, while the red curve represents the TOF signal on the circular electrostatic curved mirror；the upper right corner curve shows the contrast ratio of the free-fall reflection peak intensities between the curved and planar gravitational cavities
图 3 实线表示ND3分子在平面镜和曲面镜中的运动轨迹, 且分子的释放高度为17.5 mm: (a)分子在平面镜中的运动轨迹; (b)分子在曲面镜中的运动轨迹
Fig. 3 Trajectories of the ND3 molecules in the planar and curved mirrors, respectively, with the release height of the molecules set at 17.5 mm: (a) Trajectory of the molecules in the planar mirror; (b) Trajectory of the molecules in the curved mirror
图 4 ND3分子在两个凹面或两个平面反射镜构成的反射腔中时间飞行信号: 黑色曲线表示重氨分子在由两个平面反射镜构成的腔中反射的结果, 而红色曲线表示重氨分子在由两个曲面反射镜构成的腔中反射的结果; 反射腔的高度为15 mm, 分子束中心速度在纵向上为5 m/s, 横向上为0 m/s; 右上角曲线表示曲面腔与平面腔反射峰相对强度之比
Fig. 4 TOF signal of the ND3 molecules within the reflection cavity consisted of two concave mirrors or two planar mirrors: The black line represents the result of the ND3 molecules in the cavity composed of two planar mirrors, while the red one denotes the result in the cavity composed of two concave mirrors. The reflection cavity is 15 mm in height, and the molecules have a central velocity of 5 m/s in the longitudinal direction and 0 m/s in the transverse direction.The upper right corner curve shows the contrast ratio of reflection peak intensities between the curved and planarcavities is illustrated
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