Chen Zhiming, Zeng Jianhua
State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of Chinese Academy of Sciences, Xi'an 710119, China.
School of Science, East China University of Technology, Nanchang 330013, China.
Nanophotonics. 2022 Jun 22;11(15):3465-3474. doi: 10.1515/nanoph-2022-0213. eCollection 2022 Aug.
Optical lattices (OLs) with conventional spatial periodic /2, formed by interfering the counterpropagating laser beams with wavelength , are versatile tools to study the dynamical and static properties of ultracold atoms. OLs with subwavelength spatial structure have been realized in recent quantum-gas experiment, offering new possibility for nonlinear and quantum control of ultracold atoms at the nano scale. Herein, we study theoretically and numerically the formation, property, and dynamics of matter-wave localized gap modes of Bose-Einstein condensates loaded in a one-dimensional nanoscale dark-state OL consisted of an array of optical subwavelength barriers. The nonlinear localized modes, in the forms of on- and off-site fundamental gap solitons, and dipole ones, are demonstrated; and we uncover that, counterintuitively, these modes exhibit always a cusplike (side peaks) mode even for a deeply subwavelength adiabatic lattice, contrary to the previously reported results in conventional deep OLs where the localized gap modes are highly confined in a single lattice cell. The (in)stability features of all the predicted localized modes are verified through the linear-stability analysis and direct perturbed simulations. Our predicted results are attainable in current ultracold atoms experiments with the cutting-edge technique, pushing the nonlinear control of ultracold atoms with short-period OLs as an enabling technology into subwavelength structures.
通过使波长为λ的反向传播激光束相互干涉形成的具有传统空间周期λ/2的光学晶格（OLs），是研究超冷原子动力学和静态特性的通用工具。具有亚波长空间结构的OLs已在最近的量子气体实验中实现，为纳米尺度下超冷原子的非线性和量子控制提供了新的可能性。在此，我们从理论和数值上研究了加载在由一系列光学亚波长势垒组成的一维纳米尺度暗态OL中的玻色-爱因斯坦凝聚体的物质波局域能隙模式的形成、特性和动力学。展示了以在位和离位基本能隙孤子以及偶极孤子形式存在的非线性局域模式；并且我们发现，与直觉相反，即使对于深度亚波长绝热晶格，这些模式也总是呈现出尖峰状（边峰）模式，这与之前在传统深光学晶格中报道的结果相反，在传统深光学晶格中，局域能隙模式高度局限在单个晶格单元中。通过线性稳定性分析和直接微扰模拟验证了所有预测的局域模式的（不）稳定性特征。我们的预测结果在当前采用前沿技术的超冷原子实验中是可以实现的，将利用短周期OLs对超冷原子进行非线性控制作为一项使能技术推进到亚波长结构中。
