We present the optical properties (such as refractive index, extinction coefficient) of four layer structures, which differ only in the azo dyes layer. We used the family of azo compounds, where electron-donating and electron withdrawing groups (OCH3, CH3, Br) were introduced to the benzene ring. Then, these azo dyes were mixed with poly(3- octylthiophene) (P3OT). Afterwards, the layered structure (i.e. glass/ITO/PEDOT:PSS/azo dye+P3OT) was produced. We found that by changing the substituent in the azo compound we change the photo-physical properties of multilayer structure. Thus, we can prepare layered structures that can have potential applications in optoelectronics as photovoltaic cells or organic light-emitting diodes.
This work focuses on the fabrication processes and photonic assessment of SiO2-SnO2:Er3+ monoliths. To obtain the crack-free and densified system, the sol-gel derived synthesis protocols and heat-treatment processes were optimized. The absorption measurements were employed to assess the effect of the heat-treatment on the samples and specially to estimate the –OH content. The XRD patterns were used to investigate the crystallization as well as the structure of the monoliths. The emission spectra, performed at different excitation wavelengths, evidence the presence of Er3+ in the SnO2 nanocrystals and the energy transfer from SnO2 to the rare earth ions. In addition, the efficient role of SnO2 nanocrystals as Er3+ sensitizers are also experimentally confirmed in this system.
In this study, the 2-(4-methacryloxystyryl)quinoline, 2-(4-methacryloxystyryl)-6-methoxyquinoline were synthesized. The polymers built from the free radical polymerization of methacrylic monomers incorporating the diarylethylenes sidegroup have been synthesized in dimethylformamide with azobisisobutyronitrile as initiator. The products of polymerization were characterized and evaluated by 1HNMR, UV spectroscopy. Thermal stability was characterized by DSC method. Their optical and photochemical properties as well as temperature dependence of the photoluminescence of diarylethylenes have been investigated.
In this paper we report the synthesis of side chain methacrylic polymers functionalized with styrylquinoline fragments. The polymerization was carried out in dimethylformamide with azobisisobutyronitrile as initiator. The products of polymerization were characterized by 1H NMR, DSC. A study on the energetics of modelling compounds has been performed by a synergetic use of both electrochemical and optical techniques. The results of photochemical activities of the corresponding polymers are presented.
The aim of this work was to learn how the influence of various solvents correlates with nonlinear optical properties of metallophthalocyanines (MPcs). The method, which was used to measure nonlinear optical properties, was degenerate four wave mixing (DFWM). We used ethanol, chloroform and dimethyl sulfoxide as solvent of metallophthalocyanines. The absorption spectra of MPcs solutions present a narrow Q-band in the visible region and a relatively wide B-band in the near ultraviolet. In all cases we observed the solvatochromism effect. Nonlinear optical properties of MPcs solutions change with using different polarity of solvent in the following way: n2(ZnPc) < n2(CoPc) < n2(CuPc).
Polymers containing azobenzene dyes or azobenzene lateral groups are of special interest for their application as optically active media, particularly, as polarization sensitive media for such applications: optical data storage, surface nanostructuration, photoswitching, alignment of liquid crystals, active optical elements etc. An intensive research was carried out previous years on synthesizis and investigation of the second order nonlinear optical response of azobenzene/polymer systems. The desirable properties of these materials are attributed to the highly efficient photoinduced trans-cis and vice versa isomerization of azobenzene moieties. This transformation is connected with the volume change of molecules, followed by an increase of their rotational mobility. The trans-cis izomerization process is exploited also in all optical poling of polymers and plays an important role in optical depoling. Generally these phenomena are induced by light with frequencies corresponding to one-photon absorption. They are possible also by multiphoton absorptions. In this paper we report the synthesis of side chain methacrylic polymers functionalized with azobenzene chromophores. A reversible change of thin film absorption is observed when illuminating it with monochromatic, linearly polarized light under the applied external DC field. The amount of change depends on the angle between the light polarization and the DC electric field direction.
Third order nonlinear optical properties (NLO) of thin films of pure DNA-CTMA complex and of those doped with
disperse red 1 (DNA-CTMA-DR1) and copper phthalocyanine (DNA-CTMA-CoPc) chromophores were studied by the
optical third harmonic generation and as function of the dopant concentration. The THG measurements, performed in
vacuum at 1064 nm fundamental wavelength reveal an one orders of magnitude increase of &khgr;(3)(-3&comega;;&comega;,&comega;,&comega;) susceptibility of the DNA-CTMA complex when doped with 5% of DR1. This increase is less important for the complex
doped with CoPc. For both dopants it doesn't follow the chromophore concentration, as it could be expected. This
behavior is interpreted in terms of the influence of local field. The &khgr;(3)(-3&comega;;&comega;,&comega;,&comega;) susceptibility of pure DNA-CTMA
complex is about one order of magnitude larger than for silica plate, used as standard.
The concentration dependence of third order nonlinear optical susceptibility ( χ<3> ) of copper phthalocyanine (CuPc)
dissolved in tetrahydrofuran (THF) using the degenerate four wave mixing (DFWM) method at 532 nm was investigated.
We present the linear dependence of the third order nonlinear optical susceptibility ( χ<3> ) as a function of different
concentration for CuPc dissolved in THF. We also calculated the second order hyperpolarizability (
γ) of CuPc
solutions. Third harmonic generation (THG) measurements at the 1064 nm performed on CuPc thin films are also
presented. We found that the χ<3>DFWM values are larger than the χ<3>THG ones. This variation observed in χ<3> values,
occurs probably due to the different resonance contributions in solution and solid state of CuPc. We show that in the case
of DFWM measurements the one and two-photon resonant contributions at the Q and C-band increase χ<3>DFWM value of
CuPc. In THG measurements, the three-photon resonance contribution at the Soret band gives rise to higher χ<3>THG value.
Quantum interference of single and two photon absorption pathways connecting valence and conduction band states in a semiconductor allow one to generate spin currents with or without charge currents. The underlying principles for these generation processes are outlines. We offer experimental demonstration of pure spin currents in GaAs using two color beams configured collinearly to produce spatially homogeneous currents, or non-collinearly to produce spin current gratings.
The two photon absorption coefficient and third order nonlinear optical susceptibility of ZnSe crystals were investigated using the transmission and degenerate four wave mixing methods. The experimental results show that imaginary part of third order nonlinear optical susceptibility decrease with increase of free carriers and the absolute value of third order nonlinear optical susceptibility increase with increase of free electron concentration.
The experimental results of nonlinear optical studies at 532 nm using picosecond pulses of Zn1-xMgxSe films are reported for x equals 7%, 16% and 40%. The effects of doping on linear ((alpha) ) and nonlinear ((beta) ) absorption coefficients are investigated. All studied samples reveal a relatively strong nonlinear absorption which decreases with an increase of Mg content. The undoped sample (0% Mg) displays absorption coefficients almost equal to those of the ZnSe crystal annealed at the same temperature.