Graphene coated tilted fiber grating-based liquid refractive index sensor

Abstract

The present invention relates to a graphene coated tilted fiber grating-based liquid refractive index sensor, the surface of a tilted fiber grating gate region is coated with graphene, by change of the evanescent field distribution and transmission spectral characteristics, a surrounding liquid environment refractive index sensing sensitive area can be enlarged, and the sensitive area moves toward a low refractive index region. When the external environmental parameters (such as molecular concentration, solution refractive index and the like) change to cause graphene complex dielectric constant change so as to cause consequent changes of the effective refractive index of the fiber cladding to cause cladding mode resonance wavelength shifts and coupling strength changes of a tilted fiber grating. By extracting and analyzing of cladding mode resonance wavelength and coupling strength and cladding mode upper and lower enveloping normalized area and other spectral feature amounts, and the external environment liquid refractive index change values can be obtained. Ultimately, the liquid refractive index sensor which has high sensitivity in a low refractive index region and is free of ambient temperature influence can be achieved.

Description

technical field [0001] The invention relates to a liquid refractive index sensor based on a graphene-coated inclined optical fiber grating, which belongs to the field of optical fiber sensors, in particular to an optical fiber grating sensor for low refractive index measurement. Background technique [0002] Tilted fiber grating is a special short-period fiber grating with a certain angle between the grating surface and the fiber axis. Due to the fact that the grating surface has a certain inclination relative to the fiber axis, in addition to a part of the incident light propagating forward in the fiber is coupled into a reverse propagating core mode satisfying the Bragg condition, another part is coupled into a series of reverse propagating cladding mold. Since different mode characteristics have different sensitivities to the external environment, and the effective refractive index of the cladding mode is easily affected by the environmental refractive index, the resonan...

AI Technical Summary

Problems solved by technology

At present, the main methods to improve the perception sensitivity of the tilted fiber grating to the low refractive index region are: (1) increasing the tilt angle of the tilted fiber grating, so that the cladding mode moves to the short wavelength region. However, due to the weak coupling strength of the short wavelength, The fiber grating with a larger tilt angle of the grating surface is still difficult to achieve the sensitivity close to the cladding refractive index in the low refractive index region; (2) reduce the cladding or core diameter of the tilted fiber grating, by enhancing its ephemeral The evanescent field strength can expand the measurement range of the refractive index to a certain extent, but this method still cannot fundamentally change the low sensitivity of the tilted fiber grating to the low refractive index region, and is also easily affected by the external environment temperature

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