Department of Physics, Department of Chemistry, and JILA, University of Colorado at Boulder , Boulder, Colorado 80309, United States.
Nano Lett. 2011 Oct 12;11(10):4309-13. doi: 10.1021/nl2023299. Epub 2011 Sep 16.
The simultaneous nanometer spatial confinement and femtosecond temporal control of an optical excitation has been a long-standing challenge in optics. Previous approaches using surface plasmon polariton (SPP) resonant nanostructures or SPP waveguides have suffered from, for example, mode mismatch, or possible dependence on the phase of the driving laser field to achieve spatial localization. Here we take advantage of the intrinsic phase- and amplitude-independent nanofocusing ability of a conical noble metal tip with weak wavelength dependence over a broad bandwidth to achieve a 10 nm spatially and few-femtosecond temporally confined excitation. In combination with spectral pulse shaping and feedback on the second-harmonic response of the tip apex, we demonstrate deterministic arbitrary optical waveform control. In addition, the high efficiency of the nanofocusing tip provided by the continuous micro- to nanoscale mode transformation opens the door for spectroscopy of elementary optical excitations in matter on their natural length and time scales and enables applications from ultrafast nano-opto-electronics to single molecule quantum coherent control.
在光学领域，实现光激发的纳米级空间限制和飞秒级时间控制一直是一个长期存在的挑战。以前使用表面等离激元（SPP）共振纳米结构或 SPP 波导的方法存在模式失配等问题，或者可能依赖于驱动激光场的相位来实现空间定位。在这里，我们利用具有弱波长依赖性的锥形贵金属尖端的固有相位和幅度无关的纳米聚焦能力，在较宽的带宽内实现了 10nm 的空间和几个飞秒的时间限制激发。结合光谱脉冲整形和对尖端顶点二次谐波响应的反馈，我们演示了确定性任意光波形控制。此外，由连续的微到纳米尺度模式转换提供的纳米聚焦尖端的高效率为物质中基本光激发的光谱学开辟了道路，使其能够在自然长度和时间尺度上进行，并能够从超快纳米光电学到单分子量子相干控制等应用。
