It has been recently suggested that the nonlinear optical processes in plasmonic nanoantennas allow for a substantial boost in the sensitivity of plasmonic sensing platforms. Here, we present a sensing device based on an array of non-centrosymmetric plasmonic nanoantennas featuring enhanced second harmonic generation (SHG) integrated in a microfluidic chip. We evaluate its sensitivity both in the linear and nonlinear regime using a figure of merit that accounts for the relative change in the measured intensity, I, against the variation of the environmental refractive index n. While the signal-to-noise ratio achieved in both regimes allows attaining a resolution (i.e., minimum detectable refractive index variation) Δn_min ≈ 10^–3, the platform operation in the nonlinear regime features a sensitivity (i.e., the FOM) that is at least 3 times higher than the linear one. Thanks to the surface sensitivity of plasmon-enhanced SHG, our results show that the development of such SHG sensing platforms with sensitivity performances exceeding those of their linear counterparts is within reach.

中文翻译：

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等离子体增强的二次谐波感测

最近已经提出，等离子体纳米天线中的非线性光学过程使得等离子体传感平台的灵敏度大大提高。在这里，我们介绍了一种基于非中心对称等离子体纳米天线阵列的传感设备，其特征在于集成在微流控芯片中的增强型二次谐波（SHG）。我们使用品质因数来评估其在线性和非线性状态下的灵敏度，该品质因数说明了相对于环境折射率n的变化，测量强度I的相对变化。虽然在这两种机制实现的信噪比允许获得的分辨率（即，最小可检测的折射率变化）Δ Ñ_分钟≈10^–3，非线性条件下的平台操作具有至少比线性灵敏度高3倍的灵敏度（即FOM）。由于等离激元增强的SHG的表面灵敏度，我们的结果表明，可以实现这种灵敏度性能超过线性同类产品的SHG传感平台的开发。