Near-Field Picometer Vibration Detection Based on Dielectric Microsphere Probe

We propose a near-field picometer vibration detection method based on a dielectric microsphere probe. Using an optical fiber combined with a dielectric microsphere to form a near-field probe. When parallel light is injected into the dielectric microsphere, interaction occurs between the surface of the microsphere and the focused beam in the near field, and at the front end of the dielectric microsphere will generate a highly localized electromagnetic beam, i.e., a photonic nanojet (PNJ). The nanojet of the probe in the near-field can enhance the scattered light of the object under the test surface. We used a differential structure that was formed by two optical fiber probes to detect the picometer vibration in the near field. From the experimental results, we know that the method can detect the picometer vibration signal, while the minimum vibration signal of 20 pm can be detected. The method has the potential to apply in cellular diagnostics, single-molecule detection, and in situ measurements.