Abstract
The resonant excitation of surface plasmon–polariton waves in metal gratings with rectangular and sinusoidal relief was studied. The main characteristics of the resonant excitation of a surface plasmon–polariton wave were obtained using analytical methods due to the fact that the resonance is excited at a grating thickness much smaller than a wavelength (1.064 µm). It is shown that the obtained results are very close to those calculated using numerical methods, e.g., Rigorous Coupled Wave Approach (RCWA). There is a small difference in the numerical data defined by both methods. The difference between the parameters for the two types of gratings is small. New analytical relationships of angular and spectral sensitivities with the change of the refractive index of the medium were obtained, depending on the grating period and the angle of incidence of the light beam. An analytical relationship between the spectral and angular widths of the resonant curves, at full width at half maximum, was determined.
Highlights
Biochemical reactions occurring in liquid solutions lead to a change in the refractive index, which needs to be measured
The resonant excitation of the surface plasmon–polariton wave produces significant electric and magnetic fields, which can be of practical use in Raman spectroscopy and in the study of luminescence of a small amount of substance
It can be seen that the following where N is the ratio between the sensitivity and the spectral or angular width. The latter ratio is crucial for the sensors, because it determines the sensor’s suitability for measuring the change in the refractive index of the test medium
Summary
Biochemical reactions occurring in liquid solutions lead to a change in the refractive index, which needs to be measured. Many sensor parameters can be determined from a waveguide equation that relates the grating period, the incidence angle of the laser beam on a grating, and the propagation constant of the surface plasmon–polariton wave on the flat metal-dielectric boundary. In such structures, the resonant excitation of the surface plasmon–polariton wave produces significant electric and magnetic fields, which can be of practical use in Raman spectroscopy and in the study of luminescence of a small amount of substance. Where N is the ratio between the sensitivity and the spectral or angular width The latter ratio is crucial for the sensors, because it determines the sensor’s suitability for measuring the change in the refractive index of the test medium.
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