Nonlinear negative refraction by difference frequency generation

Negative refraction has attracted much interest for its promising capability in imaging applications. Such an effect can be implemented by negative index meta-materials, however, which are usually accompanied by high loss and demanding fabrication processes. Recently, alternative nonlinear approaches like phase conjugation and four wave mixing have shown advantages of low-loss and easy-to-implement, but associated problems like narrow accepting angles can still halt their practical applications. Here, we demonstrate theoretically and experimentally a scheme to realize negative refraction by nonlinear difference frequency generation with wide tunability, where a thin Beta barium borate slice serves as a negative refraction layer bending the input signal beam to the idler beam at a negative angle. Furthermore, we realize optical focusing effect using such nonlinear negative refraction, which may enable many potential applications in imaging science. Published by AIP Publishing.

负折射因其在成像应用中具有良好的应用前景而备受关注。这种效应可以通过负折射率超材料来实现，然而，这些材料通常伴随着高损耗以及苛刻的制造工艺。最近，诸如相位共轭和四波混频等替代的非线性方法已显示出低损耗和易于实现的优势，但诸如接收角较窄等相关问题仍然会阻碍它们的实际应用。在此，我们从理论和实验上展示了一种通过具有宽调谐性的非线性差频产生来实现负折射的方案，其中一片薄的硼酸钡晶体用作负折射层，将输入信号光束以负角度偏折到闲频光束。此外，我们利用这种非线性负折射实现了光学聚焦效应，这可能会在成像科学中带来许多潜在的应用。由美国物理联合会出版社出版。