Micro-structured optical fiber surface plasmon resonance sensor

Abstract

The invention discloses a micro-structured optical fiber surface plasmon resonance sensor, wherein a cladding layer is an annular cladding layer consisting of three concentric layers; the inner annular cladding layer consists of fan-shaped annular supporting arms (3) and inner layer air holes (2); the outer annular cladding layer consists of rectangular supporting arms (6) and outer layer liquid holes (5); the middle annular cladding layer is connected with the fan-shaped annular supporting arms (3) and the rectangular supporting arms (6); the number of both the fan-shaped annular supporting arms (3) and the rectangular supporting arms (6) is N; and the sensor has 360/No rotational symmetry. The fan-shaped annular supporting arms are used for adjusting coupling depth; and the spatial distribution of a fiber core fundamental mode is enabled to be gaussian. The operation wavelength of the sensor is at C+L wavelength; the spectral sensitivity within an analytic liquid refractive index range of 1.320-1.335 can reach over 10,000 nm RIU<1>, and the corresponding sensing resolution reaches the magnitude of 10<5> RIU; and the micro-structured optical fiber surface plasmon resonance sensor is suitable for high-accuracy real-time detection of liquid refractive index.

Description

technical field [0001] The invention relates to the design technical field of a surface plasmon resonance sensor, in particular to measuring the refractive index of a liquid by using the core fundamental mode of an optical fiber with an annular hole microstructure and the resonance principle of a surface plasmon mode to improve the measurement accuracy of the sensor. Background technique [0002] Surface plasmon resonance (SPR) sensors have important applications in the fields of chemistry, biology, environment, and medicine. In recent years, in order to realize long-distance real-time detection and system miniaturization, fiber optic SPR sensors have received extensive attention and research. At present, based on The SPR sensor of ordinary single-mode fiber still faces two major difficulties. The first is the phase matching problem between the core fundamental mode and the surface plasmon mode, that is, the real part of the effective refractive index of the two modes must be...

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Problems solved by technology

However, the core fundamental mode of this structure is a Gaussian-like mode, and there is a depression in the center of the field intensity distribution, which increases the difficulty of coupling with a common Gaussian light source; someone also proposed a SPR sensor based on a three-hole photonic crystal fiber [M. Hautakorpi , et al., “Surface-plasmon-resonance sensor based on three-hole microstructured optical fiber,” Opt. Express 16, 8427–8432(2008).], the effective core diameter of this structure is less than 1.1μm, and in visible light The region supports the single-mode operation of the Gaussian mode, which realizes the mode phase matching, and the size of the liquid filling hole is large, which is convenient for liquid filling, and the spectral sensitivity can reach 1.0·10 3 nm·RIU ?1 , because the operating wavelength is in the visible light region, the spectral sensitivity is not too high; people also proposed an H-type optical fiber SPR sensor, this structure coats a medium layer with a high refractive index on the metal layer, and realizes the core-based sensor. Phase matching between the surface plasmon mode and the surface plasmon mode [M. Erdmanis, et al., "Comprehensive numerical analysis of a surface-plasmon-resonance sensor based on an H-shaped optical fiber", Opt. Express 19, 13980–13988(2011) ], the core fundamental mode remains Gaussian mode, the operating wavelength is in the C-band, and the spectral sensitivity can reach 5.0·10 3 nm·RIU ?1 , its structure is an open structure, which optimizes the real-time sensing response time, but it is difficult to package

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