Marcela Ursache

DISPERSION CURVES COMPUTED FROM CHANNELED DIFFRACTION SPECTRA OF LIQUID CRYSTALS

Using a new version of the Talbot-Rayleigh method we recorded the I (λ) channeled spectra of uniaxial nematic liquid crystal at different temperatures. We derive the theoretical expression of I (λ) that involves a three-band model for the refractive indices, which is then fitted with the experimental data by a nonlinear optimization procedure. As a result, we compute the dispersion curves no, ne, Δn, their temperature dependencies, and the band contributions.

Light scattering in liquid crystals

In this paper we study the light scattering on the different mesophases of TBBA-CM mixture. We used He-Ne laser radiation and we derived a simple theoretical model of the diffusion process. The results are in good agreement with the data provided by other experimental methods.

ORDER PARAMETER FROM (p-ETHOXYBENZYLIDENE-)-p-n-BUTYLANILINE CHANNELED SPECTRA

The dispersion of refractive indices and birefringence of EBBA were determined at different temperatures and the band contributions to these dependencies were computed. An improved Talbot–Rayleigh experimental setup was used and, in order to increase the accuracy and minimize the computation time, a new data processing method was proposed. The temperature dependence of the order parameter and of the correction factor g, originating from the anisotropy of the local field, were computed.

Temperature dependencies of optical parameters from EBBA channeled spectra

Starting from the experimental channeled spectra I of the nematic EBBA liquid crystal and using a nonlinear optimization algorithm, we computed the dispersion curves of the ordinary and extraordinary indices, of the birefringence and the band contributions to these dependencies, as functions of the temperature. The theoretical interpretation of the spectra and the data processing technique allowed us to compute the realistic variation of the order parameter S and correction factor g with the same external parameter.

Nonlinear processes in laser radiation absorption on metallic surfaces

We performed both experimental and theoretical studies on the laser radiation absorption coefficient of a copper surface. A theoretical model for the computation of the absorption coefficient was elaborated for two-layer case (metal-oxide), taking into account the nonlinear processes which govern the dynamics of the temperature and of the widths of the layers. The experimental data and the simulation results proved to be in a very good agreement.

Multiple Layer Interference on Tbba-Cm Liquid Crystal Mixture

Abstract The new thermo-electro-optical effect consist of visible spectra colours changing under a. d.c. electric field in a time periodical temperature variation around the given temperature value. This effect was remarked using a liquid crystal mixture TBBA-CM. In this paper we explain this effect by multiple layer interference. Analysing the theoretical results we obtained a good agreement with the experimental data.

Quantized-transverse-eigenmodes coupling in optical fiber transmission systems

The spectrum of the quantized transverse eigenmodes of optoelectronic devices used in optical fiber communication systems is explicitly computed using harmonic analysis on the diamond solvable Lie group. Both analytical and numerical methods are used in order to calculate the coupling coefficients of the quantized transverse eigenmodes.

Real-ray path and image simulations for complex optical systems and 2D objects

A package of programs in Computational Optics is described, as well as the main results on rigorous solutions of the following problems: designing and optimization of optical systems, simulation for real rays tracing, computing the complete set of geometrical aberrations for well defined centered optical systems and 2D objects.