Enhanced Third-Order Optical Nonlinearity Driven by Surface-Plasmon Field Gradients
Enhanced Third-Order Optical Nonlinearity Driven by Surface-Plasmon Field Gradients
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DOI：
10.1103/physrevlett.120.203903
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发表时间：
2018-05-18
影响因子：
8.6
通讯作者：
Raschke, Markus B.
中科院分区：
文献类型：
--
作者：
Kravtsov, Vasily;AlMutairi, Sultan;Raschke, Markus B.
在小体积内有效的非线性光学混频是未来片上光子器件的关键。然而，通常低的转换效率严重限制了小型化到纳米尺度。在这里，我们证明了梯度场效应可以提供一个有效的，传统的dipoleforbidden非线性响应。我们表明，纵向非线性源电流可以主导的三阶光学非线性的自由电子响应在金在技术上重要的ncar-IR频率范围内的非线性，由于其他机制是特别小的。使用绝热纳米聚焦在空间上限制激发场，来自作为失谐ω（1）-ω（2）的函数的2 ω（1）-ω（2）四波混频响应的测量。我们发现高达10（-5）的转换效率，梯度场对psi（3）（Au）的贡献高达10（-9）m（2）/V-2。计算结果与等离子体流体力学和电子动力学理论相吻合。随着样品尺寸的减小，非线性转换效率的增加，甚至可以过度补偿体积的减小，这为增强非线性纳米光学提供了一种新的方法。这将使更有效的非线性光学设备和扩展的相干多维光谱的纳米尺度。
Efficient nonlinear optical frequency mixing in small volumes is key for future on-chip photonic devices. However, the generally low conversion efficiency severely limits miniaturization to nanoscale dimensions. Here we demonstrate that gradient-field effects can provide for an efficient, conventionally dipoleforbidden nonlinear response. We show that a longitudinal nonlinear source current can dominate the third-order optical nonlinearity of the free electron response in gold in the technologically important ncar-IR frequency range where the nonlinearities due to other mechanisms are particularly small. Using adiabatic nanofocusing to spatially confine the excitation fields, from measurements of the 2 omega(1) - omega(2) four-wave mixing response as a function of detuning omega(1) - omega(2). we find up to 10(-5) conversion efficiency with a gradient-field contribution to psi((3))(Au) of up to 10(-9) m(2)/V-2. The results are in good agreement with the theory based on plasma hydrodynamics and underlying electron dynamics. The associated increase in the nonlinear conversion efficiency with a decreasing sample size, which can even overcompensate the volume decrease, offers a new approach for enhanced nonlinear nano-optics. This will enable more efficient nonlinear optical devices and the extension of coherent multidimensional spectroscopies to the nanoscale.