We study the propagation of probe pulses carrying orbital angular momentum (OAM) in a crystal of molecular magnets characterized by a double-$\mathrm{\Lambda }$ light-matter coupling scheme. The model is based on the four-wave mixing (FWM) of applied fields interacting with the magnetic dipole moment of the molecular magnets. We consider the light-matter interaction under the situation where a weak probe field carries an optical vortex and investigate the exchange of optical vortices between different frequencies via the FWM in the microwave region. The propagation of OAM beams with nonzero radial indices is then explored. It is found that the conservation of both azimuthal and radial indices is satisfied over the swapping of OAM states of light. Superimposing two initially weak OAM modes with different topological charges creates specific vortex beams with a very characteristic form. The resulting beam contains a central vortex as well as several singly charged peripheral vortices distributed at the same radial distance from the center of the light beam. This complex pattern of vortices arises because the intensity radius of two interfering OAM modes is different. It is shown that the boundary region of intensity dominance of two OAM modes can be controlled by the molecular magnets parameters and strong cw electromagnetic fields. Our proposed scheme may provide a route to study the solid systems suitable for quantum technologies as well as for OAM exchange devices for quantum information processing.

中文翻译：

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分子磁体中的轨道角动量传递

我们研究了携带轨道角动量 (OAM) 的探测脉冲在分子磁体晶体中的传播$\mathrm{\Lambda }$光物质耦合方案。该模型基于与分子磁体的磁偶极矩相互作用的外加场的四波混合 (FWM)。我们考虑了弱探测场携带光涡流的情况下的光-物质相互作用，并通过微波区域的 FWM 研究了不同频率之间的光涡流交换。然后探索具有非零径向指数的 OAM 光束的传播。发现在交换光的 OAM 状态时，满足方位角和径向指数的守恒。叠加具有不同拓扑电荷的两种最初较弱的 OAM 模式会产生具有非常特征形式的特定涡旋光束。产生的光束包含一个中心涡旋以及几个单电荷外围涡旋，这些涡旋分布在距光束中心相同的径向距离处。出现这种复杂的涡旋模式是因为两种干扰 OAM 模式的强度半径不同。结果表明，两种OAM模式的强度优势边界区域可以通过分子磁体参数和强连续电磁场来控制。我们提出的方案可以为研究适用于量子技术以及用于量子信息处理的 OAM 交换设备的固体系统提供一条途径。结果表明，两种OAM模式的强度优势边界区域可以通过分子磁体参数和强连续电磁场来控制。我们提出的方案可以为研究适用于量子技术以及用于量子信息处理的 OAM 交换设备的固体系统提供一条途径。结果表明，两种OAM模式的强度优势边界区域可以通过分子磁体参数和强连续电磁场来控制。我们提出的方案可以为研究适用于量子技术以及用于量子信息处理的 OAM 交换设备的固体系统提供一条途径。