Nanophotonics based on high refractive index dielectrics relies on appreciable contrast between the indices of designed nanostructures and their immediate surrounding, which can be achieved by the growth of thin films on low-index substrates. Here we propose the use of high index amorphous gallium phosphide (a-GaP), fabricated by radio-frequency sputter deposition, on top of a low refractive index glass substrate and thoroughly examine its nanophotonic properties. Spectral ellipsometry of the amorphous material demonstrates the optical properties to be considerably close to crystalline gallium phosphide (c-GaP), with low-loss transparency for wavelengths longer than 650 nm. When nanostructured into nanopatches, the second harmonic (SH) response of an individual a-GaP patch is characterized to be more than two orders of magnitude larger than the as-deposited unstructured film, with an anapole-like resonant behavior. Numerical simulations are in good agreement with the experimental results over a large spectral and geometrical range. Furthermore, by studying individual a-GaP nanopatches through non-degenerate pump–probe spectroscopy with sub-10 fs pulses, we find a more than 5% ultrafast modulation of the reflectivity that is accompanied by a slower decaying free carrier contribution, caused by absorption. Our investigations reveal a potential for a-GaP as an adequate inexpensive and CMOS-compatible material for nonlinear nanophotonic applications as well as for photocatalysis.

中文翻译：

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二氧化硅上的纳米结构非晶态磷化镓，用于非线性和超快纳米光子学

基于高折射率电介质的纳米光子学依赖于设计纳米结构的折射率与其直接周围环境之间的明显对比，这可以通过在低折射率基板上生长薄膜来实现。在这里，我们建议在低折射率玻璃基板上使用通过射频溅射沉积制造的高折射率非晶磷化镓（a-GaP），并彻底检查其纳米光子性能。无定形材料的椭圆光谱表明光学性质非常接近晶体磷化镓（c-GaP），对于波长大于650 nm的光，其损耗低。当纳米结构化为纳米补丁时，单个a-GaP贴片的二次谐波（SH）响应的特征是比沉积的非结构化薄膜大两个数量级以上，并具有类似偶极子的共振行为。数值模拟与大光谱和几何范围内的实验结果非常吻合。此外，通过使用低于10 fs脉冲的非简并泵浦-探针光谱研究单个a-GaP纳米斑，我们发现反射率的超快调制超过5％，并伴随着吸收引起的较慢的衰变自由载流子贡献。我们的研究表明，a-GaP作为非线性纳米光子应用以及光催化领域中一种足够便宜且与CMOS兼容的材料的潜力。数值模拟与大光谱和几何范围内的实验结果非常吻合。此外，通过使用低于10 fs脉冲的非简并泵浦-探针光谱研究单个a-GaP纳米斑，我们发现反射率的超快调制超过5％，并伴随着吸收引起的较慢的衰变自由载流子贡献。我们的研究表明，a-GaP作为非线性纳米光子应用以及光催化领域中一种足够便宜且与CMOS兼容的材料的潜力。数值模拟与大光谱和几何范围内的实验结果非常吻合。此外，通过使用低于10 fs脉冲的非简并泵浦-探针光谱研究单个a-GaP纳米斑，我们发现反射率的超快调制超过5％，并伴随着吸收引起的较慢的衰变自由载流子贡献。我们的研究表明，a-GaP作为非线性纳米光子应用以及光催化领域中一种足够便宜且与CMOS兼容的材料的潜力。我们发现反射率超过5％的超快调制，并伴随着吸收引起的较慢的衰减自由载流子贡献。我们的研究表明，a-GaP作为非线性纳米光子应用以及光催化领域中一种足够便宜且与CMOS兼容的材料的潜力。我们发现反射率超过5％的超快调制，并伴随着吸收引起的较慢的衰减自由载流子贡献。我们的研究表明，a-GaP作为非线性纳米光子应用以及光催化领域中一种足够便宜且与CMOS兼容的材料的潜力。