Strain-based tunable hollow-peanut-shaped optical microresonator

Abstract

A mechanical strain tuning of whispering gallery mode (WGM) in a hollow-peanut-shaped optical microresonator (HPSOM) is demonstrated. The HPSOM is fabricated by fusion splicing two hollow bubbles. The central resonator is formed by the solid structure in the middle, and the near end (far end) resonator is formed by the hollow structure on both sides. The hollow microresonator can improve the strain response-ability compared with the solid micro resonant. The resonator structure and strain response characteristics of the HPSOM are researched theoretically and experimentally researched. It is worth noting that due to the elliptical effect of the central resonator during the manufacturing process, the central resonator cannot confine the light field to the equator and form the WGM. In the coupled spectrum, the WGMs of bilateral HPSOM with low Q-mode are easier to distinguish and monitor. Therefore, a low Q-mode is selected for strain measurement. The testing highest sensitivity is 6.96 pm/μɛ in the strain range 0–25 μɛ. Relative to the large-strain dynamic testing, low-strain testing has broad application prospects in geotechnical engineering testing, structural testing, and engineering geophysical prospecting. Being of general interest, our findings pave the way for improved perception of strain.