0000000000012104
AUTHOR
Mārtiņš Rutkis
Tetrathiotetracene thin film morphology and electrical properties
The electrical properties of organic thin films are determined by their chemical constituents and the morphology of the films deposited. In this paper the morphology of vacuum sublimed (7?10-6 mbar) tetrathiotetracene (TTT) thin films is shown to be strongly affected by the thermal deposition temperature (222-350 K) and rate of deposition. Mostly needle-like morphologies are identified by scanning electron microscopy. Optimal TTT purity (a pre-requisite for device preparation via subsequent oxidation) is evidenced by their initially low electrical conductivity. Altering the TTT morphology, by variation of the evaporation parameters, strongly affects this base electrical conductivity. Four p…
Optical propagation loss measurements in electro optical host-guest waveguides
Thin organic waveguiding layers are applied more and more frequently as optical components in novel optoelectronic devices. For development of such devices it is important to know the optical properties of the used waveguides. One of the most important parameters is optical propagation loss in the waveguide. In this paper we present optical propagation loss measurements in planar electro optical waveguides using travelling fiber method. Using this method attenuation coefficient α at 633 nm as a function of chromophore concentration for the first two guiding modes in the slab waveguide was determined.
Novel azobenzene precursors for NLO active polyuretanes: Synthesis, quantum chemical and experimental characterization
Abstract For the development of electro optical active polyurethanes six new derivatives of 2-{(2-hydroxyethyl)-[4-(4-nitrophenylazo)phenyl]amino}ethanol and two of 2-{(2-hydroxyethyl)-[4-(5-nitropyridin-2-ylazo)phenyl]amino}ethanol were synthesized by azocoupling reaction. Molecular geometry, hyperpolarizability βFF and ground state dipole moment μg were acquired by RHF ab initio (6–31G∗∗) calculations using HyperChem software package. To characterize NLO performance of synthesized azo compounds second order non linear coefficients d31 and d33 were measured as function of chromophore load in guest–host films (PMMA). Eight synthesized compounds can be grouped in four similar gross formula p…
EFFECTS OF THE MULTIPLE INTERNAL REFLECTION AND SAMPLE THICKNESS CHANGES ON DETERMINATION OF ELECTRO-OPTIC COEFFICIENT VALUES OF A POLYMER FILM
New nonlinear optical (NLO) active organic materials are appealing candidates for optoelectronic and photonic technologies. For the evaluation of new NLO polymer materials for applicability in the mentioned technologies, the most important criteria are their electro-optic (EO) coefficients. We have implemented the Mach–Zehnder interferometric (MZI) method for the determination of EO coefficients of thin organic films. Despite the fact that other multiple optical methods for the determination of thin film EO coefficients are known, the MZI method has been chosen because this particular technique has high sensitivity to phase and intensity modulations in the sample arm of an interferometer an…
New Figure of Merit for Tailoring Optimal Structure of the Second Order NLO Chromophore for Guest-Host Polymers
Reliability to forecast SHG efficiency using two sets of non linear optical (NLO) chromophore figures of merit (FOM) was tested. One of them predicts that SHG efficiency d 33 of the poled guest-host polymer is proportional to ground state dipole ∼ μg, another to ∼ 1/μg. Correlation of maximal achieved second order NLO efficiency of the PMMA based systems containing eight dimethylaminobenzylidene-1, 3-indandione (DMABI) related chromophores with proposed FOM have been analyzed. The best correlations were obtained with second set of FOM, especially if high dipole moment (μg > 7D) chromophores are included in analysis.
Nonlinear optical properties of low molecular organic glasses formed by triphenyl modified chromophores
The series of organic molecular glasses have been studied as possible candidates for nonlinear optical (NLO) applications. Amorphous phase formation of investigated materials is ensured by the presence of bulky triphenyl substituents in molecular structure of NLO chromophores. Linear optical properties as well as NLO coefficients and thermal stability of NLO activity for the 13 molecular materials in glassy thin solid films have been determined. For the benzylidene-1,3-indandione chromophore containing compound the highest d33 value equal to 280 pm/V was measured under the 1064 nm excitation. Among the investigated compounds uppermost achieved thermal sustainability of NLO response was 108 …
Toward device applicable second order NLO polymer materials: definition of the chromophore figure of merit
Maximal achieved second order non linear optical (NLO) efficiency of the PMMA based host – guest systems containing eight dimethylaminobenzylidene -1, 3 - indandione (DMABI) related chromophores have been analysed. Two contradicting sets of NLO chromophore figure of merit (FOM) equations were tested. One of them predicts that NLO efficiency of the poled polymer host -guest film is proportional to ground state dipole d33 ~ 1/μg, another to d33 ~ 1/μg. The best correlations for the maximal achieved nonlinearity were obtained with second set of FOM, especially if high ground state dipole (μg > 7D) chromofores are included in analysis.
Indanedione based binary chromophore supramolecular systems as a NLO active polymer composites
Novel route to obtain EO material is proposed by supramolecular assembly of neutral-ground-state (NGS) and zwitterionic (ZWI) NLO chromophores in binary chromophore organic glass (BCOG) host–guest system. On a basis of our Langeven Dynamics (LD) molecular modeling combined with quantum chemical calculations, we have shown that anticipated enhancement NLO efficiency of BCOG material is possible via electrostatic supramolecular assembly of NGS with ZWI chromophore in antiparallel manner. Binding energy of such complex could be more dependent on molecular compatibility of components and local (atomic) charge distribution, then overall molecular dipole moments. According to our LD simulations t…