Effect of finite absorption index on surface plasmon resonance in the sensor layer of optical sensors

The analysis of the thermal effect of laser radiation on the sensory effect of the three-layer structure “prism—absorbing nanolayer—water” was resumed. The influence of the laser radiation flux on the metal nanolayer can lead to its significant heating and to the same heating of the adjacent water layers. In our previous studies, the approximation of the infinite absorption coefficient of the sensor nanolayer was considered by the example of gold. We investigated the effect of the finite absorption coefficient both on the heating of the sensory system in the sensor “prism—absorbing nanolayer—water” and on the change of the plasmon resonance wavelength in it. It was defined that with a decrease in the absorption coefficient k, the radiation flux required to achieve the same temperature as at k = ∞ increases. That is, to achieve the maximum sensory effect with a decrease in the absorption coefficient of the material, an increase in the flux is required. This makes the use of highly absorbing materials preferable. The range of radiation flux, at which the influence of temperature on the sensory effect can still be neglected, as before, does not exceed 1 W/cm2 in all studied cases. The magnitude of the sensory effect on the plasmon resonance wavelength also does not change in all studied cases and is 0.75% of the initial value of the plasmon resonance wavelength. © 2023, King Abdulaziz City for Science and Technology.