We report a weighing metrology experiment of a single silica microsphere optically trapped and immersed in air. Based on fluctuations about thermal equilibrium, three different mass measurements are investigated, each arising from one of two principle methods. The first method is based on spectral analysis and enables simultaneous extraction of various system parameters. Additionally, the spectral method yields a mass measurement with systematic relative uncertainty of 3.0% in 3 s and statistical relative uncertainty of 0.9% across several trapping laser powers. Parameter values learned from the spectral method serve as input, or a calibration step, for the second method based on the equipartition theorem. The equipartition method gives two additional mass measurements with systematic and statistical relative uncertainties slightly larger than the ones obtained in the spectral method, but over a time interval 10 times shorter. Our mass estimates, which are obtained in a scenario of strong environmental coupling, have uncertainties comparable to ones obtained in force-driven metrology experiments with nanospheres in vacuum. Moreover, knowing the microsphere’s mass accurately and precisely will enable air-based sensing applications.

中文翻译：

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称重与空气处于热平衡状态的光学陷阱微球

我们报告了一个光学捕获并浸入空气中的单个二氧化硅微球的称重计量实验。基于热平衡的波动，研究了三种不同的质量测量方法，每种测量方法均来自两种主要方法之一。第一种方法基于光谱分析，可以同时提取各种系统参数。此外，光谱法还可以进行质量测量，在3 s内系统相对不确定度为3.0％，在多个陷波激光功率下的统计相对不确定度为0.9％。从光谱方法学到的参数值用作基于等分定理的第二种方法的输入或校准步骤。等分法给出了两次额外的质量测量，其系统和统计上的相对不确定度比光谱法获得的结果稍大，但时间间隔短了十倍。我们的质量估计是在强环境耦合的情况下获得的，其不确定性可与在真空中纳米球的力驱动计量实验中获得的不确定性相媲美。此外，准确而精确地了解微球的质量将使基于空气的传感应用成为可能。