Optical hysteresis is a fundamental phenomenon that can lead to optical bistability and highspeed signal processing. Here, we present a theoretical and experimental study of the optical hysteresis phenomenon in amorphous As 2 S 3 chalcogenide based waveguide structures under surface plasmon resonance (SPR) conditions. The SPR structure is irradiated with low power CW Ar laser radiation at 514 nm wavelength, with photon energy near the optical band-gap of As 2 S 3 , in a Kretschmann-Raether configuration. First, we determined the incidence angle on the SPR structure for resonant coupling of the laser radiation within the waveguide structure. Subsequently, by setting the near resonance incidence angle, we analyzed the variation of the laser power reflected on the SPR structure with incident power. We demonstrated that, by setting the incidence angle at a value slightly smaller than the resonance angle, the increase followed by the decrease of the incident power lead to a wide (up to 60%) hysteresis loop of the reflected power. This behavior is related to the slow and persistent photo-induced modification of the complex refractive index of As 2 S 3 under 514 nm laser irradiation. The experimental and theoretical results are in good agreement, demonstrating the validity of the theoretical model presented here.

Following the interaction of a neutrino with saline environment, the Cherenkov cone will be generated. The electromagnetic effect of the Cherenkov cone is perpendicular to the cone generator and it has the energy directly proportional to the neutrino energy. In the saline environment, neutrinos with very high energies (noise-115 dBm) can be determined. Investigation of these neutrinos will lead to the construction of a Cherenkov detector. The construction of a Cherenkov detector involves the design and the construction of a very large number of detection elements and of cascade amplifiers. Another necessary condition is to know exactly the distribution of the dielectric parameters of the saline environment. In order to know the distribution of the dielectric parameters of the saline environment, it is necessary to make a map of their distribution. Under these conditions, the number of detection elements will be optimized and also the optimal position of the future Cherenkov detector will be determined. In this chapter, we will present the methodology of calculating the detection elements and a method to determine the dielectric parameters. Measurements of attenuation of the propagation of electromagnetic waves in this environment will be presented. We will detail how to optimize a Cherenkov detector.

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Studies were carried out in order to investigate the sensitivity of some thin films, to ultraviolet light, based on barium stearate and carbon nanotubes structures. A three – five monolayers structures were developed using the Langmuir – Blodgett technique onto ceramic substrate. Obtained Langmuir – Blodgett complex thin films shows sensitivity to ultra violet light radiation, taking into consideration the presence of carbon nanotubes that facilitates the charge carriers transport. Also the investigations performed, revealed the properties of carbon nanotubes and point out the fine chemistry of these materials. Based on this premise we proceed to investigate and characterize the photo – electrical behavior of the obtained structures.