Coherent upconversion of terahertz and mid-infrared signals into visible light opens new horizons for spectroscopy, imaging, and sensing but represents a challenge for conventional nonlinear optics. Here, we used a plasmonic nanocavity hosting a few hundred molecules to demonstrate optomechanical transduction of submicrowatt continuous-wave signals from the mid-infrared (32 terahertz) onto the visible domain at ambient conditions. The incoming field resonantly drives a collective molecular vibration, which imprints a coherent modulation on a visible pump laser and results in upconverted Raman sidebands with subnatural linewidth. Our dual-band nanocavity offers an estimated 13 orders of magnitude enhancement in upconversion efficiency per molecule. Our results demonstrate that molecular cavity optomechanics is a flexible paradigm for frequency conversion leveraging tailorable molecular and plasmonic properties.

中文翻译：

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具有分子光机械纳米腔的连续波频率上转换

太赫兹和中红外信号到可见光的相干上转换为光谱学、成像和传感开辟了新的视野，但对传统的非线性光学来说是一个挑战。在这里，我们使用包含数百个分子的等离子体纳米腔来展示在环境条件下将亚微瓦连续波信号从中红外（32 太赫兹）到可见域的光机械转换。入射场共振驱动集体分子振动，这在可见泵浦激光器上留下相干调制，并导致上转换的拉曼边带具有低于自然的线宽。我们的双波段纳米腔使每个分子的上转换效率提高了 13 个数量级。