ICFO, Institut de Ciences Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain.
CNR-INO and LENS, European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, Sesto Fiorentino, 50019 Firenze, Italy.
Nano Lett. 2020 Sep 9;20(9):6756-6762. doi: 10.1021/acs.nanolett.0c02607. Epub 2020 Aug 25.
Optical nanoantennas are well-known for the confinement of light into nanoscale hot spots, suitable for emission enhancement and sensing applications. Here, we show how control of the antenna dimensions allows tuning the local optical phase, hence turning a hot spot into a cold spot. We manipulate the local intensity exploiting the interference between driving and scattered field. Using single molecules as local detectors, we experimentally show the creation of subwavelength pockets with full suppression of the driving field. Remarkably, together with the cold excitation spots, we observe inhibition of emission by the phase-tuned nanoantenna. The fluorescence lifetime of a molecule scanned in such volumes becomes longer, showing slow down of spontaneous decay. In conclusion, the spatial phase of a nanoantenna is a powerful knob to tune between enhancement and inhibition in a 3-dimensional subwavelength volume.
光学纳米天线以将光限制在纳米级热点中而闻名，非常适合发射增强和传感应用。在这里，我们展示了如何通过控制天线尺寸来调整局部光学相位，从而将热点变成冷点。我们利用驱动场和散射场之间的干涉来控制局部强度。使用单分子作为局部探测器，我们通过实验证明了可以创建具有完全抑制驱动场的亚波长口袋。值得注意的是，除了冷激发点外，我们还观察到相位调谐纳米天线抑制了发射。在这样的体积中扫描的分子的荧光寿命变长，表明自发衰减减慢。总之，纳米天线的空间相位是在三维亚波长体积中在增强和抑制之间进行调谐的强大旋钮。
