Like a candle in the wind: flicker noise in nano-optomechanical systems

机械系统（包括纳米机电系统 (NEMS) 和纳米光机械系统 (NOMS)）的频率稳定性水平对其性能至关重要，无论是作为超灵敏传感器还是作为参考振荡器。我们领域最近的工作表明，这种性能几乎从未像人们所希望的那样受到热机械噪声的基本噪声源的限制，而是几乎总是受到频率闪烁噪声的限制。最近的一项突破 [Roy, ​​Sauer, Westwood-Bachman, Venkatasubramanian, Hiebert (2018) Science 360​​, eaar5220] 得出了令人惊讶的结果，即通过降低品质因数（增加阻尼）可以保持甚至提高精密机械谐振器的性能。阻尼频率稳定性的改善似乎与通过周围（阻尼）空气的热传导抑制这种普遍存在的闪烁噪声有关。继这项突破性工作之后，我们寻求探索闪烁噪声对 NEMS 和 NOMS 频率稳定性的影响。使用以下调节旋钮：空气阻尼、器件尺寸、器件温度系数（可通过内应力调节）、光机弹簧调谐、光机耦合和温度，我们将彻底探索和了解 NOMS 器件中闪烁噪声的来源，确定两个竞争模型中的哪一个可以解释整个参数空间中的噪声。一旦充分理解，我们将设计设备来最小化和消除这种噪声，以达到 NOMS 系统的基本噪声水平和最终频率稳定性极限。将空气阻尼及其闪烁缓解通道与高精度光机械相结合，即使在高阻尼条件下，NOMS 器件也能实现自振荡。这种在环境空气中运行的 NOMS 振荡器的极限频率稳定性最终将导致传感器技术的深刻进步，例如空气中的单 Da 质谱分析。

The frequency stability level of mechanical systems, including nanoelectromechanical systems (NEMS) and nano-optomechanical systems (NOMS), is of paramount importance to their performance, both as ultrasensitive sensors, and as reference oscillators. Recent work in our field has shown that this performance is almost never limited by the fundamental noise source of thermomechanical noise, as one would desire, but rather is almost always limited by frequency flicker noise. A recent breakthrough [Roy, Sauer, Westwood-Bachman, Venkatasubramanian, Hiebert (2018) Science 360, eaar5220] established the surprising result that precision mechanical resonator performance can be maintained and even improved by reducing quality factor (increasing damping). The improvement in frequency stability with damping seems to be related to suppression of this ubiquitous flicker noise through the thermal conduction of surrounding (damping) air. Following on from this breakthrough work, we seek to explore the realm of flicker noise contribution to NEMS and NOMS frequency stability. Using tuning knobs of: air damping, device dimension, device temperature coefficient (tunable through internal stress), optomechanical spring tuning, optomechanical coupling, and temperature, we will thoroughly explore and understand the source of flicker noise in NOMS devices, identifying which of two competing models explain the noise throughout this parameter space. Once well-understood, we will design devices to minimize and eliminate this noise in order to reach the fundamental noise level, and ultimate frequency stability limit, of NOMS systems. Combining air damping and its flicker mitigation channel with high-finesse optomechanics will allow self-oscillation of NOMS devices even in highly-damped conditions. Ultimate limit frequency stability in such NOMS oscillators that operate in ambient air will ultimately lead to profound advancements in sensor technology, such as single-Da mass spectrometry in air.