Trends in the development of modern sensory devices based on surface plasmon resonance (SPR) are considered. The basic principles of construction of SPR sensor are given. For excitation of surface plasmons on the surface of sensitive elements of biosensory, a prism of total internal reflection is used or a dielectric substrate are used. A thin (dozens nm) film of high-conductive metal (mainly gold or silver) is applied to the working surface of the prisms or dielectric substrate. In a typical observation experiment, SPR is measured dependence on the angle of increasing light intensity, reflected by the resonance sensitive surface of the prism (chip).
The optical schemes and principles of work of various SPR sensors are considered:
– SPR Sensors with angular modulation, which are the most commonly used method based on the corner registration, in which the SPR occurs. The surface of the metal film is irradiated by monochromatic light and scans on a certain range of angles. There is a kind of SPR sensors with angular modulation, in which there is no mechanical scan of the angle of fall. Such sensors are entirely necessary for excitation of PPRs a set of angles is obtained due to a divergent or convergent light beam. SPR sensors with amplitude modulation in which the modulation is performed at a fixed angle of incidence and wavelength, while the measuring signal is determined based on the change in resonance intensity.
– PPR sensors with a wavelength modulation is based on fixing an angle of falling light at a certain value and modulation of the wavelength of the incident light. Excitation of surface plasmons leads to a characteristic failure in the spectrum of reflected radiation.
– Phase sensitive SPR sensors in which a change in the phase of the light wave associated with the surface plasma is measured on one corner of the fall and the wavelength of the light wave and is used as the output signal.
– SPR imaging sensors in which the Technology of SPR imaging (SPRi) combines the sensitivity of the SPR with spatial image capabilities. The SPRI circuit uses as a fixed angle (as a rule, a slightly left angle of the SPR) and a fixed wavelength to measure changes in the reflection ability (Δ% R) that occur when the curve of the SPR is shifted due to the change in the refractive index above the surface of the sensor element.
– SPR imaging sensors polarization contrast. In order to improve the quality of high-performance SPR imaging sensors in terms of sensitivity and resolution, the method of polarization contrast is used
Disadvantages and advantages of SPR sensors are constructed with different principles are considered. The design and prospect of the use of achromatic and superachromatic wave plates in the PPR imaging sensors with polarization contrast are considered.
A.V. Samoylov. Optoelectron. Semicond. Tech. 56, 5-26 (2021)