Large-capacity high-resolution optomechanical mass sensing based on free-space optical cavity.

Mass sensing offering both a broad detection range and a high resolving power is essential for quantitative precision content analysis and high-yield mass production of various kinds of materials. Here, we propose and successfully demonstrate a novel type of simple low-cost optomechanical mass sensing employing an optical displacement detector that consists of a free-space Fabry-Pérot optical cavity and an intra-cavity wedge prism pair, which provides an enhanced resolution and an extended capacity simultaneously. By implementing the null-method-based scheme of mass measurement, we achieve a resolution higher than 5000:1 (mass range from <200 mg to >1 kg) and an excellent linearity of R2>0.99998 in the prototype demonstration.