All-fiber microfluidic multimode Mach–Zehnder interferometers as high sensitivity refractive index sensors

Femtosecond laser direct writing of a 3D microcantilever on the tip of an optical fiber sensor for on-chip optofluidic sensing

“…Among the transmission style sensors, optical fiber sensors based on MZI and evanescent wave principles are the most common, which can be prepared by simple processes such as arc discharge welding and tapering fibers. 9,11,20 Since auxiliary processes such as femtosecond lasers are not necessary, their fabrication methods are relatively simple, but the refractive index sensitivity of this type of sensor is low. Although SPR sensor has a high refractive index sensitivity, it is also transmission structure, 19 which will increase the performance of microfluidic chips as described in this paper.…”

“…1,6,7 Among different sensors used in microfluidic systems, optical fiber sensors are highly anticipated for the distinct advantages of the corrosion resistance, small size and biocompatibility. [8][9][10] Common optical fiber sensing principles include Mach-Zehnder interferometer (MZI), 11 Raman scattering, 12 surface plasmon resonance (SPR), [13][14][15][16][17][18][19] optical evanescent wave, 20,21 grating 22,23 and F-P. [24][25][26][27][28][29][30][31] In microfluidic systems, optical fiber sensors can be divided into the transmission types 12,[17][18][19][20]22 and the insertion types [24][25][26][27][28][29][30][31] according to the integration mode of the sensor and chip. For instance, Raman scattering sensor 12 and SPR sensors 17,19 are implanted in microfluidic channels to measure liquid concentrations.…”