Maker Fringe Method Research Articles

New symmetrical pi-conjugated molecules having large third-order optical nonlinearities

New symmetrical pi-conjugated molecules having large third-order nonlinear susceptibilities, χ(3), are reported. The χ(3) spectra of these molecules have been measured by a THG Maker-fringe method. The magnitudes of the three-photon resonant χ(3) reach 10−10 esu. The positions of the three-photon resonance lie at the lowest-energy peaks in the vibrational structure of each absorption spectra for these molecules.

Preparation and Nonlinear Optical Property of Polydiacetylenes from Dialkyltetraacetylene Compounds

Abstract To obtain polydiacetylenes with π-conjugation between polymer backbone and side chains, diacetylene monomers with acetylenic substituents, i.e., dialkyltetraacetylene compounds, were synthesized. It has been found that they were highly polymerizable on UV or γ-ray irradiation and became deeply blue-colored polymers. It was confirmed that the polymerization proceed topochemically via 1,4-addition to give polydiacetylenes with acetylenic substituents. Third order nonlinear optical susceptibility of these polymers, evaluated from third harmonic generation by Maker fringe method, were larger than that of the corresponding dialkyldiacetylene polymer.

Excitonic resonant effect in the third-order nonlinear optical properties of blue- and red-form polydiacetylene films

The third-order nonlinear optical susceptibility |χ (3)| has been evaluated for blue- and red-form polydiacetylene (PDA) oriented films by means of the Maker fringe method. For the red-form PDA, care was taken to minimize the conformation disorder effect. The observed |χ (3)| spectra for the blue- and red-form films show prominent peaks at about 0.65 (blue) and 2.35 eV (red) which are just three-photon resonant to the 1B u excitons located at 1.95 (blue) and 2.35 eV (red) in the respective forms of PDA. The results are discussed by a three-level model taking account of the results of electro-absorption measurements on the same films.

The quality and performance of the organometallic complex nonlinear optical material tri-allylthiourea cadmium chloride (ATCC)

Large (30x30x25 mm) crystals of the organometallic, nonlinear optical material ATCC have been prepared by growth from solution in optically and structurally highly perfect state. Type I phase-matched SHG was observed for 1.064 μm radiation incident at 36.8°. The whole nonlinear coefficient was carried out by Maker-fringe (MF) method.

Nonlinear Optical Studies of Mixed π-Conjugated Polymer Multilayers by Second Harmonic Generation

ABSTRACTThe structures of the mixed LB monolayers, composed of two different kinds of π-conjugated system, poly(3-hexylthiophene) (PHT) and pentacosa-10, 12-diynoic acid (DA), have been investigated mainly by a second harmonic generation (SHG) Maker fringe method. The mixed LB films partly contain a double-layered structure consisting of PHT and DA. The second harmonic radiation has been produced from slightly twisted PHT in the double layer. Both UV-polymerization of DA and successive heat-treatments enhanced the SHG intensities. The enhancement of the SHG intensities has been elucidated by the enlargement of the PHT twisting and the interaction between PHT and a newly formed π-conjugated system.

Optical nonlinearity of conjugated polymers

Third order harmonic generation measurements on polythiophene were done by using Maker fringe method. It is found that third-order nonlinear susceptibility of polythiophene is as large as that of polyacetylene at the wavelength of 1907 nm. The value of X (3) is 3.52 × 10 −10 esu.

Nonlinear optical properties of an azo dye attached polymer

Copolymers of azo dye substituted acrylic monomer and methylmethacrylate are synthesized and their third-order nonlinear optical susceptibility χ(3) is evaluated using the third harmonic generation Maker fringe method. The χ(3) is 1.26×10−12 esu at 25.9 mol % azo dye monomer content in the copolymer. It is also shown that there is a linear relationship between χ(3) and the monomer content.

Linear and nonlinear optical properties of Ca 3(VO 4) 2

Single crystals of Ca 3 (VO 4) 2 have been grown by the Czochralski method. The refractive indices show that the crystals are phasematchable between 1.72 μm and 2.94 μm with favourable values for acceptance angle and spectral width of the incident laser beam in the entire phasematching range. The nonlinear optical coefficients have been measured by the Maker fringe method at a fundamental wavelength of 1.064 μm. They are comparable to those of KDP. Thus the crystals are potentially useful for frequency conversion of broadband or tunable laser sources as semiconductor and F-center lasers. They may also be installed in high f-number IR image converters.

Measurement of Second Harmonic Generation in (NH4)2SO4

The Second Harmonic Generation has been studied on (NH 4 ) 2 SO 4 single crystal in the ferroelectric phase mainly for the purpose of providing useful information to unravel the microscopic origin of permanent dipoles. All values necessary for detailed analysis of independent components of SHG coefficient have been obtained as a function of temperature by Maker fringe method. It has been found that each component has a dull peak respectively at about -100°C, with peak values d 31 =0.54, d 32 =0.59 and d 33 =1.3 relative to d 11 in quartz. The relative signs have been also determined experimentally as d 31 · d 33 <0 and d 32 · d 33 <0 respectively.

Temperature dependence of optical nonlinear susceptibility of NaNO2

Abstract All values of non-vanishing components, χij of the optical nonlinear susceptibility in NaNO2 have been accurately measured by a Maker-fringe method. The relative signs were also determined directly. As a result, we have χ31·χ33 < 0, χ32·χ33 > 0 and χ24·χ33 > 0. Further it has been found that the respective χij varies in a different manner with temperature over the range from 40°C to Tc , i.e., χ33 exhibits a remarkable temperature-dependence while χ32 and χ24 vary as Ps . The present results reveal that NaNO2 shows a rather anomalous nonlinear response as compared with other ferroelectric materials.