Valeriy Yatsishen, Volgograd State University, Russia
Potapova I.I., Volgograd State University, Russia
Surface plasmons (SP) are collective excitations that occur in conductors under the condition that the real part of the complex permittivity is negative. Recently, SP is widely used in the diagnosis of various materials. In this case, the studied object is placed at the interface between the metal and air, on which the conditions for the excitation of surface plasmons are created. As a result, the angle of the minimum reflection of the light wave shifts. For the transmitted wave, a similar shift in the angle of the maximum wave intensity occurs. The resulting shifts of the minimum and maximum are characteristic of this material.
Surface waves occur in both environments under certain conditions, they attenuate into the depth of each of them according to the exponential law.
Schema of the diagnosis of a biological object with the help of excitation of SP in the Otto configuration consist of a prism, an air gap and a metal layer. Gold was used as a metal at the boundary of which SP was excited, whose dielectric constant at a wavelength of λ = 633 nm is complex with a negative real part ε3= -11.86+1.2i. The biological object forms an additional layer. As such, we have chosen a tissue sample with a dielectric constant ε4=1.96. In addition to the reflection spectra, we offer the use of angular transmission spectra for these purposes. We calculate the angular reflection and transmission spectra. This dependence demonstrates the capabilities of transmission spectroscopy taking into account the excitation of surface polaritons.
The analysis performed shows that the distance between the minimum (in the case of reflection) and the maximum (for transmission) peaks is about 5⁰ and clearly demonstrates the sensory capabilities of the method of exciting surface plasmons in the diagnosis of biological objects. We carried out calculations for a large number of biological objects and obtained results for angular spectra. We emphasize that a single point of reference in all cases is the minimum in the reflection spectrum of RRp, when there is only a layer of gold.
Prof. Valeriy Vasil'evich Yatsishen
Volgograd State University, Professor
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