Temperature-insensitive miniaturized fiber inline Fabry-Perot interferometer for highly sensitive refractive index measurement

Abstract

We report a miniaturized fiber inline Fabry-Perot interferometer (FPI), with an open micro-notch cavity fabricated by one-step fs laser micromachining, for highly sensitive refractive index measurement. The device was tested for measurement of the refractive indices of various liquids including isopropanol, acetone and methanol at room temperature, as well as the temperature-dependent refractive index of deionized water from 3 to 90 degrees C. The sensitivity for measurement of refractive index change of water was 1163 nm/RIU at the wavelength of 1550 nm. The temperature cross-sensitivity of the device was about 1.1x10(-6) RIU/degrees C. The small size, all-fiber structure, small temperature dependence, linear response and high sensitivity, make the device attractive for chemical and biological sensing.

Note: Optical fiber milled by focused ion beam and its application for Fabry-Pérot refractive index sensor

“…The fiber constitutes the backbone conduit for light guiding, and effective light-fluid interaction is achieved when the microfluidic channel intersects the optical pathway. In recent years, devices such as microchannels, microslots, and FP interferometers have been fabricated in single-mode fibers (SMFs) by the use of femtosecond laser micromachining, [8][9][10][11][12] which can be effectively utilized for RI sensing with low temperature sensitivity and large dynamic range. However, a relative low fringe visibility of the interference pattern is achieved when using this technique for making FP fiber sensors.…”

“…[1][2][3][4][5][6][7][10][11][12] This improved fringe visibility is mainly due to the finely polished end facets and precisely milled parallel two end walls of the microcavity. A sensitivity of ∼1731 nm/RIU and a detection limit of ∼5.78 × 10 −6 RIU can be achieved, which is comparable to the FP sensitivity reported by other groups [1][2][3][4][5][6][7][10][11][12] and exceeds the 1500 nm/RIU demonstrated for long period grating based RI sensors in PCFs. 18 It is still a long way from the 70 000 nm/RIU predicted for two-core PCF coupler based RI sensors, 19,20 but the FP technology in standard SMF is more simple and robust.…”

Ball Lens Based Common Path Fiber Optic Interferometer Sensor

“…Traditional bulk refractometers are then not appropriate because of their size and weight. Fiber optic sensor is widely used for compactness, cost-effectiveness, flexibility, and multiplexing capability [4,5]. Espcially, at measurement of RI, the interferometric techniques use the interference between a sample beam and reference beam.…”

“…Their packaging for practical usages is not simple also. Furthermore, these reflective methods using fiber optic cannot be used for the liguid whose RI exceeds the fiber core index [5]. In this paper, we report the implementation of the sensing probe that can satisfy long working distance, massroduction, and reproducibility to be a sensing probe for measurement of refractive index.…”

Low-Cost Fiber-Tip Fabry-Perot Interferometer and Its Application for Transverse Load Sensing

“…As one kind of optical fiber sensors [1][2][3][4][5], fiber optic Fabry-Perot interferometers (FPIs), which offer the advantages of high resolution, compact structure and immunity to electromagnetic interference, play important roles in a large number of sensing applications such as refractive index [6][7][8][9], strain [10][11][12], temperature [13][14][15], pressure [16][17][18] and so on. Among them, the Fabry-Perot cavity which is fabricated at the fiber tip can be effectively used in space limited environment.…”