The strong nonlinear optical response of two-dimensional materials has applications in bioimaging and integrated optical information processing; however, past experiments were on diffraction limited samples or required intense pulsed lasers, which is a detriment to potential applications due to cost, power and complexity. Here we show that second harmonic generation can be achieved from single subwavelength two-dimensional material nanoflakes smaller than the diffraction limit using a plasmonic optical tweezer with a low-power (down to 3 mW) laser diode operating in continuous-wave mode. A double nanohole plasmonic tweezer enhances the local field and the local density of optical states to allow for trapping and significant nonlinear generation at the nanoscale. Also, the fact that it is a two-dimensional material means that it can be positioned closer to the highest field regions, realizing 2 orders of magnitude higher power second harmonic generation than other nonlinear materials like lithium niobate. The ability to have simple high efficiency nonlinear generation at the nanoscale will benefit future nonlinear optics applications of these emerging materials.

中文翻译：

---

具有超低泵浦功率的单纳米片六方氮化硼谐波生成

二维材料的强非线性光学响应在生物成像和集成光信息处理方面有应用；然而，过去的实验是在衍射受限的样品上进行的，或者需要强脉冲激光，由于成本、功率和复杂性，这对潜在应用是不利的。在这里，我们展示了使用等离子体光镊和低功率（低至 3 mW）激光二极管在连续波模式下工作，可以从小于衍射极限的单个亚波长二维材料纳米薄片中产生二次谐波。双纳米孔等离子体镊子增强了局部场和光学状态的局部密度，以允许在纳米尺度上捕获和显着非线性生成。还，它是一种二维材料，这意味着它可以放置在更靠近最高场区域的位置，与铌酸锂等其他非线性材料相比，它可以实现高 2 个数量级的二次谐波产生。在纳米级进行简单高效非线性生成的能力将有利于这些新兴材料的未来非线性光学应用。