In comparison to classical input or output grating couplers, GMR

In comparison to classical input or output grating couplers, GMR optical biosensors differ distinctly from traditional sensors in their operational principle and functionality [4,5]. Gemcitabine FDA Wawro et al. presented a method using fiber optic sensor integrating dielectric diffraction gratings and thin films on optical fiber endfaces for biomedical sensing applications [6]. In2002, Cunningham et al. discussed the use of these resonant elements as biosensors, capable of resolving changes of 0.1 nm in a sample. They also make it possible to quickly measure a large number of molecular interactions taking place simultaneously upon a grating surface. Moreover, they can monitor reactions in real time [7�C10]. Furthermore, Cunningham et al. improved the sensitivity by changing the GMR structure [8].
The polarization of the incident light is a key factor in the sensitivity of this kind of optical biosensor. Magnusson et al. emphasized polarization-based parametric discrimination and presented that resonant sensors can be designed to support two or more leaky modes in the spectral band of interest [11]. Electric field distribution analysis (EFDA) can reveal the difference the Transverse Electric (TE) and Transverse Magnetic (TM) modes have on sensitivity. This article presents a comparison of sensitivity in the TE and TM modes using EFDA. It is found that sensitivity in the TM mode is three times that achieved in the TE mode.Magnusson and Lee introduced a phase modulation method [12,13], which is more complex than the amplitude modulation method, so the amplitude method is used in this article.
When molecules are attached to the surface, the reflected wavelength (color) is shifted due to a change in the optical path of light that is coupled into the grating. In this article, the appropriate parameters of a GMR biosensor structure are determined and the sensitivity of the different modes of incident light is shown. Then the sensitivity of the TE and TM modes of incident light is compared by the EFDA.2.?ModelThe structure of the GMR optical biosensor is shown in Figure 1. From top to bottom, the GMR optical biosensor includes a cover layer (air), a sample layer (biological samples, such as protein molecules), a grating layer, a waveguide layer, and a substrate layer (quartz glass).
Based on the theory of the optical waveguide, the effective Carfilzomib index of the i-th order diffracted wave should be in the range followed with Equation (1) in [14]:maxnc,ns��|��i/k0|=|ncsin��-i��/��|Ganetespib cancer �� = 500 nm, dw = 101 nm, dg = 120 nm.Here, nc and ns are the refractive index of the sample layer and the substrate, �� is the propagation constant, k0 is the wave number, �� is the incident angle, �� is the resonant wavelength, and �� is the period of the grating layer.

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