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Large optical nonlinearity enabled by coupled metallic quantum wells

2019; Springer Nature; Volume: 8; Issue: 1 Linguagem: Inglês

10.1038/s41377-019-0123-4

2095-5545

Haoliang Qian, Shilong Li, Ching‐Fu Chen, Su‐Wen Hsu, Steven Edward Bopp, Qian Ma, Andrea R. Tao, Zhaowei Liu,

Advanced Fiber Laser Technologies

Abstract New materials that exhibit strong second-order optical nonlinearities at a desired operational frequency are of paramount importance for nonlinear optics. Giant second-order susceptibility χ (2) has been obtained in semiconductor quantum wells (QWs). Unfortunately, the limited confining potential in semiconductor QWs causes formidable challenges in scaling such a scheme to the visible/near-infrared (NIR) frequencies for more vital nonlinear-optic applications. Here, we introduce a metal/dielectric heterostructured platform, i.e., TiN/Al 2 O 3 epitaxial multilayers, to overcome that limitation. This platform has an extremely high χ (2) of approximately 1500 pm/V at NIR frequencies. By combining the aforementioned heterostructure with the large electric field enhancement afforded by a nanostructured metasurface, the power efficiency of second harmonic generation (SHG) achieved 10 −4 at an incident pulse intensity of 10 GW/cm 2 , which is an improvement of several orders of magnitude compared to that of previous demonstrations from nonlinear surfaces at similar frequencies. The proposed quantum-engineered heterostructures enable efficient wave mixing at visible/NIR frequencies into ultracompact nonlinear optical devices.