等离子体纳米结构附近四能级量子系统中非线性光学现象和空间结构光学效应的控制
Control of nonlinear optical phenomena and spatially structured optical effects in a four-level quantum system near a plasmonic nanostructure
摘要：
研究了位于金属包覆的二维介质球阵列附近的四能级双V型量子系统与一对弱探测场相互作用时的非线性光学响应.这样的量子系统包含一个与表面等离子体相互作用的V型子系统，以及另一个与自由空间真空相互作用的V型子系统。所提出的设置的一个显着特点是当放置在等离子体纳米结构附近时，其对所施加的场的相对相位的灵敏度。我们证明，由于存在的等离子体纳米结构，三阶（克尔型）的激光场之一的磁化率可以显着修改，而另一个探测场的作用。此外，通过改变量子系统与等离子体纳米结构的距离，可以控制甚至增强系统的Kerr非线性，并且通过调节外加场的相对相位可以控制系统的Kerr非线性.所得结果可能在片上纳米光子器件中找到潜在的应用。我们还研究了当一个探测场带有光涡旋，而另一个探测场没有光涡旋时的光-物质相互作用。我们证明了由于闭环双V型量子系统的相位敏感性，非涡旋探测光束的线性和非线性极化率依赖于涡旋探测光束的方位角和轨道角动量（OAM）.在与自由空间真空相互作用的开放四能级双V型量子系统中，由于没有量子干涉发生，因此不存在这种特征。我们使用量子系统的光学磁化率的方位角依赖性来确定空间结构透射率的区域。
英文摘要：
We investigate the nonlinear optical response of a four-level double-V-type quantum system interacting with a pair of weak probe fields while located near a two-dimensional array of metal-coated dielectric nanospheres. Such a quantum system contains a V-type subsystem interacting with surface plasmons, and another V-type subsystem interacting with the free-space vacuum. A distinctive feature of the proposed setup is its sensitivity to the relative phase of the applied fields when placed near the plasmonic nanostructure. We demonstrate that due to the presence of the plasmonic nanostructure, the third-order (Kerr-type) susceptibility for one of the laser fields can be significantly modified while another probe field is acting. Moreover, the Kerr nonlinearity of the system can be controlled and even enhanced by varying the distance of the quantum system from the plasmonic nanostructure.We also show that the Kerr nonlinearity of such a system can be controlled by adjusting the relative phase of the applied fields. The results obtained may find potential applications in on-chip nanoscale photonic devices. We also study the light-matter interaction in the case where one probe field carries an optical vortex, and another probe field has no vortex. We demonstrate that due to the phase sensitivity of the closed-loop double V-type quantum system, the linear and nonlinear susceptibility of the nonvortex probe beam depends on the azimuthal angle and orbital angular momentum (OAM) of the vortex probe beam. This feature is missing in open four-level double V-type quantum system interacting with free-space vacuum, as no quantum interference occurs in this case. We use the azimuthal dependence of optical susceptibility of the quantum system to determine the regions of spatially-structured transmittance.
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