Undamaged measurement of the sub-micron diaphragm and gap by tri-beam interference

Yanping Chen, Shen Liu, Zhongyuan Sun, Lin Zhang, Namita Sahoo, Junxian Luo, Yuanyuan Zhao, Changrui Liao, Bin Du, Chi Li, Yiping Wang

Research output: Contribution to journalArticlepeer-review


A simple, high-accuracy and non-destructive method for the measurement of diaphragm thickness and microgap width based on modulated tri-beam interference is demonstrated. With this method, a theoretical estimation error less than 0.5% for a diaphragm thickness of ~1 μm is achievable. Several fiber-tip air bubbles with different diaphragm thicknesses (6.25, 5.0, 2.5 and 1.25 μm) were fabricated to verify our proposed measurement method. Furthermore, an improved technique was introduced by immersing the measured object into a liquid environment to simplify a four-beam interference into tri-beam one. By applying this improved technique, the diaphragm thickness of a fabricated in-fiber rectangular air bubble is measured to be about 1.47 μm, and the averaged microgap width of a standard silica capillary is measured to be about 10.07 μm, giving a corresponding measurement error only 1.27% compared with actual scanning electron microscope (SEM) results.
Original languageEnglish
Pages (from-to)5840 - 5847
JournalJournal of Lightwave Technology
Issue number23
Early online date10 Sept 2019
Publication statusPublished - 1 Dec 2019

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