Martin Bösch

PARAMETRIC INTERACTIONS IN THE ORGANIC SALT 4-N, N-DIMETHYLAMINO-4'-N'-METHYL-STILBAZOLIUM TOSYLATE AT TELECOMMUNICATION WAVELENGTHS

We show that the organic salt 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate, originally developed for electro-optic applications, is also a very interesting material for phase-matched parametric interactions such as frequency-doubling and optic parametric oscillation in the near infrared. These favorable properties are due to the large off-diagonal element d26 which gives measured effective phase-matchable nonlinear optical coefficients of deff=31±5 and 15±3 pm/V at the telecommunication wavelengths of λ=1313 and 1535 nm, respectively.

Importance of intermolecular interactions in the nonlinear optical properties of poled polymers

A series of phenylbithiophene stilbenes and phenyltetraenes were synthesized and their first-order molecular hyperpolarizabilities determined. Optical nonlinearities up to μβo=9300×10−69 C m5/V were measured at 1907 nm. We show that intermolecular interactions have a large influence on the optical nonlinearity of the molecules in solution and in guest-host polymers with polymethylmethacrylate and polyquinoline as the host. We propose the use of a bulky donor group and a side chain perpendicular to the molecule’s conjugate bridge to reduce aggregation. Electro-optic coefficients as high as r33=30 pm/V at 1.55 μm in polymethylmethacrylate with 25 wt % chromophore loading were measured.

DAST a high optical nonlinearity organic crystal

Abstract We show that the organic salt 4- N , N -dimethylamino-4′- N ′-methyl-stilbazolium tosylate (DAST), developed for electro-optic applications, also is an interesting material for phase-matched parametric interactions such as frequency-doubling and optic parametric oscillation in the near infrared. Based on measured refractive indices we predict configurations for phase matched frequency doubling and promising tuning ranges for optical parametric oscillation. We determined experimentally a figure of merit for frequency doubling, d eff 2 / n 3 =230 pm 2 /V 2 at 1313 nm which is almost 30 times the one of KNbO 3 (7.9 pm 2 /V 2 ) or 120 times the one of KTP (1.9 pm 2 /V 2 ).

Novel electro-optic molecular cocrystals with ideal chromophoric orientation and large second-order optical nonlinearities

We show, for the first time to our knowledge, that highly nonlinear optically active as well as orientationally optimized crystalline materials for second-order nonlinear optics can be prepared by a proper design of short hydrogen-bonded molecular aggregates derived from a specially developed merocyanine dye. One of the cocrystals is shown to be a very useful and highly efficient crystalline material for electro-optic devices because of the perfect chromophoric orientation, the large electro-optic coefficient r111=30±3 pm/V at λ=1535 nm, and the greatly improved physical properties such as higher melting point and crystal properties such as crystallinity. In addition, we demonstrate that one can vary or tune the linear and nonlinear optical properties of this cocrystal without modifying the chromophoric orientation in the crystal lattice by changing the crystal growth conditions.

Second-Order Nonlinear Optical Organic Materials: Recent Developments

This chapter presents an overview of the current status of second-order nonlinear optical organic materials for their use in photonic applications such as optical frequency converters and electro-optic modulators. Special emphasis is placed on the material aspects and a thorough discussion of presently available substances. The potential of organic materials for third-order nonlinear optical applications has been presented in detail in Chap. 2. Earlier reviews of organic nonlinear optical materials covering different physical and material aspects can be found in [3.1–8].

Nonlinear optical properties of polymers containing a new azophenylbenzoxazole chromophore

The synthesis of the new highly extended chromophore 2-[4-(N,N-dihydroxyethylaminophenylazo)-phenyl]benzoxazole is described. Two polymers obtained by the polycondensation of this chromophore with propyloxyterephthalic acid and 2,4-tolylenediisocyanate and one obtained by the polycondensation of 2-[4-N,N-bis(2-hydroxyethyl)aminophenyl]-6-nitro-benzoxazole with 2,4-tolylenediisocyanate have been prepared and characterized. The polymers are amorphous and exhibit good optical clarity, satisfactory thermal stability above the glass transition temperature and are soluble in common organic solvents. Second order nonlinear optical behavior of the polymers has been studied through measurement of the electrooptic coefficient on films poled between parallel electrodes. The maximum value measured for the electrooptic coefficient (r33) is 6.5 pm/V at an incident laser wavelength of 1.552 mm. q 2001 Elsevier Science Ltd. All rights reserved.

Organic Materials for Second-Order Nonlinear Optics

Organic materials have become of great importance with regard to their nonlinear optical and electro-optic properties. They have attracted attention for applications in areas such as efficient frequency-conversion and high-speed light modulation. As a special feature their macroscopic properties arise from the properties of the constituent molecules. There are several possibilities to arrange these molecules macroscopically. The most common forms are single crystals [1-5], polymers [2, 6], and Langmuir-Blodgett films [7]. Besides these cases there exist other interesting concepts such as e.g. molecular beam deposition for the preparation of thin films. Since the macroscopic nonlinearity arises from the constituent molecules, the optimization of a material for a certain application consists of two steps. On the one hand, the nonlinear optical properties of the molecules have to be maximized and, on the other hand, the arrangement of these molecules in crystals or thin films has to be optimized.

A highly efficient organic second-order nonlinear optical crystal based on a donor-acceptor substituted 4-nitrophenylhydrazone

We present a novel organic crystal, 5-(methylthio)-thiophenecarboxaldehyde-4-nitrophenylhydrazone, with a large effective phase-matchable nonlinear optical coefficient, deff=29±3 pm/V at λ=1318 nm. Single crystals of dimensions up to 25×5×5 mm3 were grown. The large off-diagonal nonlinear optical coefficients can be explained with the two-dimensional geometry of the chromophores in the crystal lattice. Our crystal is ideally suited for optic parametric oscillation in the wavelength range from 1000 to 2500 nm.

In-plane alignment of noncentrosymmetric molecules by oblique-incidence molecular beam deposition

The preferential orientation of noncentrosymmetric, organic molecules with intermolecular bonding is realized by means of oblique-incidence molecular beam deposition. The in-plane anisotropy in the optical properties of the thin films is shown by transmission spectra of ultraviolet light. Second-harmonic generation measurements demonstrate the preferential orientation of the molecules aligned in-plane. In addition, the dependence of the second-harmonic light intensity on the film thickness reveals the dominance of bulk effects with respect to surface contributions. Therefore, this molecular alignment technique is a promising method to produce stable thin films for applications in linear and nonlinear optics.

Photochemical stability of highly nonlinear optical bithiophene chromophores

Abstract The photochemical stability of highly nonlinear optical bithiophene chromophores is investigated. Experiments in guest–host systems were performed in polymethylmethacrylate (PMMA) hosts for several differently modified bithiophenes and compared to Disperse Red 1 (DR1). The photochemical stability at visible wavelengths indicates that these chromophores are excellent candidates for electro-optic applications. Furthermore, one of the bithiophene chromophores was also investigated in the infrared region up to telecommunication wavelengths.