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利用近共振激光驻波场操纵中性原子实现纳米级条纹沉积是一种新型的研制纳米结构长度标准传递方法。在会聚原子过程中,由于沉积基片的存在,激光驻波场内会产生直边衍射现象,从而影响原子的运动轨迹及沉积光栅。建立了直边衍射扰动下激光驻波场模型,通过四阶龙格-库塔法,对铬原子的三维运动轨迹及沉积效果进行仿真。考虑到激光功率与失谐量的影响,从半峰全宽(FWHM)和对比度入手,对铬原子运动轨迹及沉积条纹特性进行分析。结果表明,当激光功率为3.93mW,失谐量为200 MHz时,原子沉积光栅的FWHM为6.043nm,对比度为0.863,原子沉积光栅的质量最佳。与经典模型相比,该模型考虑了驻波场中直边衍射的影响,所得模拟结果更接近实际,对实验有理论指导意义。
Nano-stripe deposition is a new method of developing nanostructured length standards using near-resonance laser standing wave fields to manipulate neutral atoms. In the process of converging atoms, the diffraction of the straight-edge laser in the standing wave field of the laser will occur due to the deposition of the substrate, which will affect the trajectories of the atoms and the deposition of the grating. The laser standing wave field model with direct-edge diffraction perturbation is established. By means of fourth-order Runge-Kutta method, the 3D trajectories and deposition effects of chromium atom are simulated. Considering the influence of laser power and detuning, the motion trajectories of chromium atoms and the characteristics of deposition stripes were analyzed based on FWHM and contrast. The results show that when the laser power is 3.93mW and the detuning amount is 200 MHz, the FWHM of the atomic deposition grating is 6.043nm and the contrast ratio is 0.863. The atomic deposition grating has the best quality. Compared with the classical model, the model considers the influence of the straight edge diffraction in the standing wave field. The simulation results obtained are more realistic and have theoretical guidance for the experiment.