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.

In this paper we present several numerical simulations of the surface plasmon resonance for Kretschmann type configuration in a metal-chalcogenide waveguide. We assume that the chalcogenide (GaLaS) waveguide layer have finite thickness, whereas the gold film layer and the air cover layer are semi-infinite layers (from an optical point of view). We determined the thickness of the chalcogenide film for which plasmonic resonant coupling of the incident radiation to the waveguide occurs. We calculated the propagation constant for the TE-and TM-modes (both for visible and IR domain), the attenuation coefficient and the electromagnetic field distribution within the waveguide. The obtained results provide the conditions for design an optical memory device 2D based on light-light interaction in plasmonic configuration. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 05/16/2015 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 9258 92582H-5 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 05/16/2015 Terms of Use: http://spiedl.org/terms

Harmonics generation in plasma by high-power pulsed lasers is an important task for plasma diagnosis. This is because of the strong relationship between the plasma characteristics and the properties of the harmonics radiation. Here we analyze the spatial and temporal properties of third harmonic (TH) radiation generated by focusing ns and fs laser pulses in air at intensities of the order of tens of TW/cm2. The air is considered a non-dispersive non-linear (NL) medium due to the low density ofN2 ions in the breakdown plasma produced under the laser pulses. We address the influence of the pump laser intensity on the properties of TH radiation. We find theoretically and experimentally that the intensity of TH radiation at the output of the NL medium increases linearly with third power of the pump peak intensity, both for ns and fs laser pulses. In case of fs pulses, we demonstrate that TH pulse duration decreases with pump intensity, in correlation to the air breakdown plasma properties. In case of ns laser pulses, we demonstrate that the TH beam diameter is two times smaller than the fundamental’s. The theoretical results on the dependence of the TH signal to the driving peak intensity are supported by experimental data. We further analyze the influence of the gamma radiation on the several commercially optical fibers that are usually employed in the laser-target interaction area. The radiation effects such as photo-darkening induced in optical fibers can severely decrease the performance of optical transmission. We investigated the change of optical transmission induced by gamma-ray radiation. Multimode optical fibers, with a core diameter of 200 μm (usable in UV, ultra-highvacuum and high temperatures conditions), were investigated in order to evaluate their possible use for diagnosis of plasmas produced by high power lasers. The optical properties were studied by analyzing the transmitted spectra of the fibers before and after irradiation, demonstrating a decrease of the measured spectrum of the optical fiber output when increasing gamma dose to 16 kGy. The results are important from both fundamental and practical points of view, providing an efficient tool for prediction of the non-linear optical phenomena in laser produced plasmas and for non-contact diagnosis of the harmonics-generating plasmas.

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In this paper we report some experimental and theoretical results concerning the characterization of the Er + 3 :Ti:LiNbO 3 and Ti:LiNbO 3 optical waveguides using the near-field measurements at 1540 nm wavelength. The near-field measurements have been performed using a standard fibre probe for the scanning of the waveguide transversal section, but also an infrared vidicon camera. Using the Helmholtz scalar equation and a deconvolution procedure we evaluated some parameters which characterize Er + 3 :Ti:LiNbO 3 waveguides: the refractive-index difference and the penetration depth. Also, we evaluated the coupling loss coefficients between a standard optical fibre and Ti:LiNbO 3 and Er + 3 :Ti:LiNbO 3 optical waveguides for λ =1.54 μ m.