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Selectively infiltrated photonic crystal fibers for strain measurement with ultra-high sensitivity

An ultrasensitive strain sensor is demonstrated by selectively filling one of the air holes in the photonic crystal fiber. Light propagated in the photonic crystal fiber core can be coupled to the liquid-filled rod-waveguide efficiently under phase-matching conditions. The resonant wavelength, which corresponds to the coupling between the fundamental core mode and the fundamental mode of the adjacent liquid rod waveguide, experiences large shift by applying axial strain. The experimental results obtained show that the strain sensitivity achieved is ~394.6 pm/με, which is one or two orders higher than that of conventional fiber gratings.