School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Nano Lett. 2012 Feb 8;12(2):932-7. doi: 10.1021/nl204002u. Epub 2012 Jan 27.
The optomechanical coupling that emerges in an optical cavity in which one of the mirrors is a mechanical resonator has allowed sub-Kelvin cooling with the prospect of observing quantum phenomena and self-sustained oscillators with very high spectral purity. Both applications clearly benefit from the use of the smallest possible mechanical resonator. Unfortunately, the optomechanical coupling largely decays when the size of the mechanical system is below the light wavelength. Here, we propose to exploit the optical resonances associated to the light confinement in subwavelength structures to circumvent this limitation, efficiently extending optomechanics to nanoscale objects. We demonstrate this mechanism with suspended silicon nanowires. We are able to optically cool the mechanical vibration of the nanowires from room temperature to 30-40 K or to obtain regenerative mechanical oscillation with a frequency stability of about one part per million. The reported optomechanical phenomena can be exploited for developing cost-optimized mass sensors with sensitivities in the zeptogram range.
在一个光学腔中，其中一个反射镜是机械谐振器，这种光学机械耦合使得亚开尔文冷却成为可能，有望观察到量子现象和具有极高光谱纯度的自维持振荡器。这两种应用都明显受益于使用尽可能小的机械谐振器。不幸的是，当机械系统的尺寸小于光波长时，光机械耦合会大大衰减。在这里，我们建议利用与亚波长结构中的光限制相关的光学共振来规避这一限制，从而有效地将光机械学扩展到纳米尺度的物体。我们用悬浮硅纳米线来演示这种机制。我们能够将纳米线的机械振动从室温冷却到 30-40 K，或者获得具有约百万分之一频率稳定性的再生机械振荡。所报道的光机械现象可用于开发成本优化的纳克级灵敏度质量传感器。
