It is predicted that an orbital angular momentum (OAM) carried by an elliptic Gaussian beam (EGB) with a cross‐phase can induce an effective anisotropic diffraction (AD). At the so‐called critical OAM, such an OAM‐induced AD makes the spiraling elliptic Gaussian mode, which expands owing to the diffraction while keeping its elliptic degree changeless, exist in linearly isotropic media, where only the circular Gaussian mode is supposed to exist for a beam without an OAM. In this study, such a phenomenon is experimentally demonstrated via the propagations of the EGBs with the OAM in linearly and both‐linearly‐and‐nonlinearly isotropic media. In the former case, the spiraling elliptic Gaussian mode is observed at the critical OAM in the free space. In the latter case, the spiraling elliptic soliton predicted by Desyatnikov et al. is observed for the first time in cylindrical lead glass. The physics behind the spiraling elliptic soliton is the OAM‐induced AD, which preserves the elliptic degree of the EGB, whereas the nonlinearity only balances the diffraction of the EGB. The OAM‐induced AD is just a linear effect and has nothing to do with nonlinearity.

中文翻译：

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横向交叉相位对线性和非线性状态下光束传播的影响

可以预见，椭圆高斯光束（EGB）携带的具有交叉相位的轨道角动量（OAM）可以引起有效的各向异性衍射（AD）。在所谓的临界OAM中，这样的OAM诱导的AD使线性椭圆各向同性介质中存在螺旋形的椭圆高斯模，该椭圆高斯模由于衍射而扩展，同时保持其椭圆度不变，仅存在于圆形高斯模中没有OAM的光束。在这项研究中，通过EGB与OAM在线性，线性和非线性各向同性介质中的传播，通过实验证明了这种现象。在前一种情况下，在自由空间中的临界OAM处会观察到螺旋椭圆高斯模态。在后一种情况下，Desyatnikov等人预测了螺旋椭圆孤子。首次在圆柱形铅玻璃中观察到。螺旋形椭圆孤子背后的物理学是由OAM引起的AD，它保留了EGB的椭圆度，而非线性仅平衡了EGB的衍射。OAM引起的AD只是线性效应，与非线性无关。