Quantum optics has advanced our understanding of the nature of light and enabled applications far beyond what is possible with classical light. The unique capabilities of quantum light have inspired the migration of some conceptual ideas to the realm of classical optics, focusing on replicating and exploiting non-trivial quantum states of discrete-variable systems. Here, we further develop this paradigm by building the analogy of quantum squeezed states using classical structured light. We have found that the mechanism of squeezing, responsible for beating the standard quantum limit in quantum optics, allows for overcoming the “standard spatial limit” in classical optics: the light beam can be “squeezed” along one of the transverse directions in real space (at the expense of its enlargement along the orthogonal direction), where its width becomes smaller than that of the corresponding fundamental Gaussian mode. We show that classical squeezing enables nearly sub-diffraction and superoscillatory light focusing, which is also accompanied by the nanoscale phase gradient of the size in the order of λ/100 (λ/1000), demonstrated in the experiment (simulations). Crucially, the squeezing mechanism allows for continuous tuning of both features by varying the squeezing parameter, thus providing distinctive flexibility for optical microscopy and metrology beyond the diffraction limit and suggesting further exploration of classical analogies of quantum effects.

量子光学加深了我们对光本质的理解，并使应用远远超出了经典光所能实现的。量子光的独特能力激发了一些概念思想向经典光学领域的迁移，专注于复制和利用离散变量系统的非平凡量子态。在这里，我们通过使用经典结构光构建量子压缩态的类比来进一步发展这一范式。我们发现，负责突破量子光学中标准量子极限的挤压机制可以克服经典光学中的“标准空间极限”：光束可以沿实际空间中的横向之一“挤压”（以沿正交方向扩大为代价），其中其宽度变得小于相应的基本高斯模式的宽度。我们表明，经典压缩可实现近亚衍射和超振荡光聚焦，这也伴随着大小为 λ/100 （λ/1000） 的纳米级相位梯度，在实验（模拟）中得到了证明。至关重要的是，压缩机制允许通过改变压缩参数来连续调整这两个特征，从而为超越衍射极限的光学显微镜和计量学提供独特的灵活性，并建议进一步探索量子效应的经典类比。