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

作为超灵敏传感器和参考振荡器，包括纳米机电系统（NEMS）和纳米光机械系统（NOMS）在内的机械系统的频率稳定水平对其性能至关重要。在我们的领域，最近的工作表明，这种性能几乎从来没有受到热力学噪声的基本噪声源的限制，正如人们所希望的那样，而是几乎总是受到频闪噪声的限制。最近的一项突破[Roy， Sauer, Westwood-Bachman, Venkatasubramanian, Hiebert (2018) Science 360， eaar5220]建立了一个令人惊讶的结果，即通过降低质量因子（增加阻尼）可以保持甚至提高精密机械谐振器的性能。有阻尼的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无处不在的闪烁噪声有关。在这项突破性工作的基础上，我们寻求探索闪烁噪声对NEMS和NOMS频率稳定性的贡献。利用空气阻尼、器件尺寸、器件温度系数（可通过内应力调节）、光机械弹簧调谐、光机械耦合和温度的调谐旋钮，我们将深入探索和了解NOMS器件中闪烁噪声的来源，确定两种相互竞争的模型中哪一种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，以尽量减少和消除这种噪声，以达到基本噪声水平，最终频率稳定极限，NOMS系统。将空气阻尼及其闪烁缓解通道与高精细光力学相结合，即使在高阻尼条件下，NOMS设备也可以实现自振荡。这种在环境空气中工作的NOMS振荡器的最终极限频率稳定性将最终导致传感器技术的深刻进步，例如空气中的单da质谱。

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.