Hollow-glass-microsphere-assisted half-circle interference for hydrostatic pressure measurement with high sensitivity

We propose and demonstrate a half-circle interferometer using a hollow glass microsphere (HGM) resonator. The half-circle interference is induced by a mismatch between the fundamental mode in the HGM and the modes in the capillary wall. The theoretical model is verified by comparing the simulated and experimental results. The variation in capillary length induced by the axial pressure contributes the most to the half-circle interference, which features a device with a high hydrostatic pressure sensitivity of -1.099 nm/kPa. This device shows potential as a hydrostatic pressure sensor owing to its stability, high sensitivity, and robustness.