Mondal Abhishek, Das Ritwick
Opt Lett. 2022 Aug 1;47(15):3668-3671. doi: 10.1364/OL.460995.
Quantum mechanical Stern-Gerlach (SG)-like effects are unusual to explore in the domain of optics due to the absence of any interaction of photons or optical waves with the conventional magnetic field. A few recent investigations point toward the possibility of observing an SG-like effect in nonlinear optics via wedge-shaped poling in a long lithium niobate (LN) crystal to generate a spatially varying analogous magnetic field (→). This leads to two different propagation directions for the mutually orthogonal states formed by superposition of signal and idler modes (states) with opposite phases. In this work, we present theoretical formalism to show an equivalent SG-like splitting in a frequency downconversion process and experimentally validate the assertion by producing a suitable transverse gradient in → through an in-homogeneous pump wavefront. The experimental results show SG-like splitting in an optical parametric generation (OPG) process using a widely used periodically poled LN (PPLN) crystal and a pump laser exhibiting a suitable spatial beam profile. The experimentally measured deviation angle for the mutual beam closely matches with the prediction from theoretical formalism using a Gaussian pump wavefront.
由于光子或光波与传统磁场不存在任何相互作用，在光学领域探索类似量子力学斯特恩-盖拉赫（SG）效应的现象并不常见。最近的一些研究表明，通过在长铌酸锂（LN）晶体中进行楔形极化以产生空间变化的类似磁场（→），有可能在非线性光学中观察到类似SG效应。这导致由具有相反相位的信号和闲频模式（状态）叠加形成的相互正交状态有两个不同的传播方向。在这项工作中，我们提出理论形式来展示频率下转换过程中的等效类似SG分裂，并通过非均匀泵浦波前在→中产生合适的横向梯度来实验验证这一论断。实验结果表明，在使用广泛应用的周期性极化铌酸锂（PPLN）晶体和具有合适空间光束轮廓的泵浦激光的光学参量产生（OPG）过程中存在类似SG分裂。使用高斯泵浦波前时，实验测量的相互光束的偏转角与理论形式的预测结果非常吻合。
