Ecole Polytechnique Fédérale de Lausanne, EPFL, 1015 Lausanne, Switzerland.
Nat Nanotechnol. 2012 Aug;7(8):509-14. doi: 10.1038/nnano.2012.97. Epub 2012 Jun 24.
Nanoscale mechanical oscillators are used as ultrasensitive detectors of force, mass and charge. Nanomechanical oscillators have also been coupled with optical and electronic resonators to explore the quantum properties of mechanical systems. Here, we report an optomechanical transducer in which a Si(3)N(4) nanomechanical beam is coupled to a disk-shaped optical resonator made of silica on a single chip. We demonstrate a force sensitivity of 74 aN Hz(-1/2) at room temperature with a readout stability better than 1% at the minute scale. Our system is particularly suited for the detection of very weak incoherent forces, which is difficult with existing approaches because the force resolution scales with the fourth root of the averaging time. By applying dissipative feedback based on radiation pressure, we significantly relax this constraint and are able to detect an incoherent force with a force spectral density of just 15 aN Hz(-1/2) (which is 25 times less than the thermal noise) within 35 s of averaging time (which is 30 times less than the averaging time that would be needed in the absence of feedback). It is envisaged that our hybrid on-chip transducer could improve the performance of various forms of force microscopy.
纳米机械振荡器可用作力、质量和电荷的超灵敏探测器。纳米机械振荡器还与光学和电子谐振器耦合，以探索机械系统的量子特性。在这里，我们报告了一种光机械换能器，其中 Si(3)N(4)纳米机械梁与单个芯片上的二氧化硅制成的盘状光学谐振器耦合。我们在室温下实现了 74 aN Hz(-1/2)的力灵敏度，在分钟级的时间内，读出稳定性优于 1%。我们的系统特别适合于检测非常弱的非相干力，这对于现有方法来说是困难的，因为力分辨率与平均时间的四次方根成比例。通过应用基于辐射压力的耗散反馈，我们显著放宽了这一限制，并能够在 35 s 的平均时间内（比没有反馈时所需的平均时间少 30 倍）检测到仅为 15 aN Hz(-1/2)的非相干力（比热噪声低 25 倍）。预计我们的混合片上换能器可以提高各种形式的力显微镜的性能。
