Mechanism Of Enhanced Grating-Coupled Surface Plasmon Resonance Sensor

The signal enhancement and filtering function of surface plasmon resonance (SPR)sensor was achieved by use of the locality of surface plasmon polaritons (SPP) and theselectivity of grating on the basis of metal grating coupled. In this paper, based on thephysical characteristics of surface plasmon, analysis the physical mechanism of surfaceplasmon enhancement of grating on the metal film using finite difference time domainnumerical simulation method combined with the experiment. And analysis informationof the detected objects from transmittance spectroscopy of grating coupled SPR sensor.We research from theory, the analog design of the grating, the device processingtechnology and testingAccording to the basic theory of electromagnetic interaction with matter-Maxwellequations, discussed the condition of the surface plasmon excitation, propagationcharacteristics, and local enhancement characteristics. Grating transmission phenomenaof the physical mechanism is attributed to the role of surface plasmon results by use ofthe numerical results of FDTD solution. Changes of the dielectric permittivity of themetal surface causes the change of the resonance peak position of the transmissionspectrum, use this mechanism to be applied in the detection of biological, chemical.For grating-coupled SPR sensor, combined with the simulated results, consider thecycle of the grating, metal materials, and other parameters on the grating transmissioncharacteristics, design and optimize the structure of the grating. Set the grating period of1.6μm and2μm, enhancement and resonance in the transmission spectra of thecorresponding wavelength range, in the role of the near-infrared wavelength of incidentlight. Based on simulation results, the use of magnetron sputtering, the stepper UVlithography, ion beam dry etching and plasma enhanced chemical vapor deposition andother experimental methods prepare grating and SPR sensor. On the basis of the largenumber of experiments to optimize the technical parameters, such as metrology ofstepper lithography machine and the power of the ion beam etching etc. The lithographyoptimal measurement is expose168and focus1.0. form better lines, which have steep sidewall. It as the foundation of ion beam etching, the current of ion beam is80mA,neutralized current is100ma, argon flow rate is5.2sccm and the gold etching rate is37nm/min.Testing and observation of the transmission characteristics of the grating, foundthat the grating period of1.6μm and2.0μm, respectively, center wavelength ofexcitation resonance peaks in the transmission spectrum is1.8μm and2.3μm,respectively. Transmission spectrum for SPR sensor test of the different substances anddifferent concentrations of the same material, show that period of one-dimensionalmetal grating are2.0μm, but different media on metal surface, the permittivity is1and1.8496, respectively, center wavelength of excitation resonance peaks in thetransmission spectrum is2.3μm and2.2μm. When the metal surface covered with thesame medium, but the concentration of volatile from1s to5s, so that permittivitychange, center wavelength of excitation resonance peaks change, in the transmissionspectrum.The results suggested that the characteristic information of physics, biological andchemical of the object can be tested by means of peak position change of the SPRtransmission spectra when the medium in the metal film grating SPR sensor waschanged.