No abstract

With diameter close to the wavelength of the guided light and high index contrast between the fiber and the surrounding, an optical micro-fiber shows a variety of interesting waveguiding properties, including widely tailorable optical confinement, strong evanescent fields and waveguide dispersion. Among various micro-fiber applications, optical sensing has been attracting increasing research interest due to its possibilities of realizing miniaturized fiber optic sensors with small footprint, high sensitivity, and low optical power consumption. Typical micro-fiber based sensing structures, including Michelson interferometer, Mach-Zenhder interferometer, Fabry-Perot interferometer, micro-fiber ring resonator, have been proposed. The sensitivity of these structures heavily related to the fraction of evanescent field outside micro-fiber. In this paper, we report the first theoretical and experimental study of a new type of refractometric sensor based on micro-fiber three-beam interferometer. Theoretical and experimental analysis reveals that the sensitivity is not only determined by the fraction of evanescent field outside the micro-fiber but also related to the values of interferometric arms. The sensitivity can be enhanced significantly when the effective lengths of the interferometric arms tends to be equal. We argue that this has great potential for increasing the sensitivity of refractive index detection.

Silica microwire, as an optical waveguide whose diameter is close to or smaller than the wavelength of the guided light, is of great interest because it exhibits a number of excellent properties such as tight confinement, large evanescent fields, and great configurability. Here, we report a silica microwire-based compact photonic sensor for real-time detection of high electric field. This device contains an interferometer with propylene carbonate cladding. Based on the Kerr electro-optic effect of propylene carbonate, the applied intensive transient electric field can change the refractive index of propylene carbonate, which shifts the interferometric fringe. Therefore, the electric field could be demodulated by monitoring the fringe shift. The sensor was successfully used to detect alternating electric field with frequency of 50 Hz and impulse electric field with duration time of 200 μs. This work lays a foundation for future applications in electric field sensing.

A novel optical current sensor based on microfiber knot resonator (MKR) with magnetic fluid (MF) as cladding is proposed and demonstrated in this paper. The operating principles, package technique and mounting method of the proposed sensor are introduced in detail. Moreover, the performances of the proposed sensor are demonstrated experimentally by detecting sinusoidal current with 50Hz and pulse current signals with rising time of 2.5μs respectively. The results have shown that the relationship between the sensor responding and the applied current intensity is approximately linear and the minimal detectable current is 10 Amps with SNR (Signal-to-noise ratio) as 3.