Michael Canva

Effect of temperature and atmospheric environment on the photodegradation of some Disperse Red 1-type polymers.

The photodegradation of the azobenzene chromophore DR1 {4-[N-ethyl-N-(2-hydroxyethyl)amino]-4(?)-nitroazobenzene]} incorporated as a side chain or as a guest in a poly(methyl) methacrylate host has been evaluated as a function of wavelength, temperature, and the atmospheric environment. The effects of these variables on the lifetime of DR1-based electro-optic devices is quantified.

Wavelength dependence of 4-dimethylamino-4′-nitrostilbene polymer thin film photodegradation

The polymeric electro-optical stilbene material, 4-dimethylamino-4′-nitrostilbene (DANS), was illuminated at wavelengths ranging from the visible to near-infrared in order to quantify its photodegradation processes. Photodegradation due to one-photon and two-photon absorption was studied. The quantum efficiency of the chromophore degradation is found to be strongly wavelength and absorption mechanism dependent. This suggests that, in different regions of the spectrum, different excited states or different mechanisms are involved in the degradation process. In the near-infrared spectral region, operation lifetimes of electro-optic devices made from this chromophore are expected to be around only few hundreds hours, dramatically shorter than it was previously believed.

Systematic behavior of electro-optic chromophore photostability

The wavelength dependence of the one-photon absorption-induced photodegradation rate has been measured from the visible to the near IR for a variety of electro-optic chromophore-doped polymers. Systematic behavior is identified. The lifetime of the electro-optic activity is found to increase exponentially over 4-6 orders of magnitude for wavelengths ranging from peak of absorption, typically in the visible, to ~1000 nm. Many popular chromophores developed for electro-optics over the past 10 years are compared.

QUADRATIC SPATIAL SOLITON GENERATION BY SEEDED DOWNCONVERSION OF A STRONG HARMONIC PUMP BEAM

Two-dimensional quadratic spatial solitons were generated experimentally near phase-matching conditions for type II frequency doubling in KTP by the seeding of a strong second-harmonic field with a weak input at the fundamental wavelength. The self-trapped beams were shown to be insensitive to the energy, phase, and polarization of the fundamental-frequency seed input beam.

Properties of type II quadratic solitons excited by imbalanced fundamental waves.

It was shown experimentally for type II second-harmonic generation in KTP that the family of quadratic spatial solitons exists over a wide range of imbalances for the two fundamental wave inputs. The threshold for soliton formation was measured as a function of both phase mismatch and relative input fraction of the energy in the two fundamental polarizations. Launching unequal fundamental inputs led to an imbalanced three-coupled-field output composition.

Local and external factors affecting the photodegradation of 4N,N′-dimethylamino-4′nitrostilbene polymer films

The photodegradation of the electro-optic chromophore 4N,N′-dimethylamino-4′nitrostilbene was investigated as a function of wavelength, temperature, local atmosphere, and local molecular environment, i.e., attached as a side chain to a polymer or dissolved as a guest in a host polymer.

Robust generation, properties and potential applications of quadratic spatial solitons generated by optical parametric amplification

Quadratic spatial solitary waves are predicted and observed experimentally near degeneracy for Type II optical parametric amplification in bulk KTP, by seeding an intense pump optical field with a control signal at half the pump wave frequency. The self-trapping of light at the two wavelengths has been shown to be insensitive to phase, polarization and magnitude of the control input, and can be exploited in novel schemes for robust all-optical processing.

Relative electrical resistivities and poling of nonlinear optical polymeric waveguides

A method based on Maker fringe measurements of nonlinear optical coefficients has been used to determine the relative dc electrical resistivities of a series of linear and nonlinear optical polymers. The method can be used to identify low resistivity linear cladding materials for optimized electric field poling of nonlinear optical polymeric waveguides. As an example of the application of the technique we have studied the resistivity of poly(methyl methacrylate)-polystyrene (PMMA-PS) copolymers with varying content of the two components. The resistivity of PMMA was found to be one order of magnitude lower than that of PS.

Second-harmonic generation in reactive-ion etched N′ ethyl N-ethanol-4-(nitrophenylazo)phenylamino polymer waveguides at telecommunication wavelengths

Second-harmonic generation using modal dispersion phase matching has been demonstrated in reactive-ion etched waveguides based on the organic nonlinear polymer poly (methyl methacrylate)-Disperse Red 1 [N′ ethyl N-ethanol-4-(nitrophenylazo)phenylamino]. The measured propagation losses were 6 dB/cm at the fundamental and 10 dB/cm at the second-harmonic wavelength, dramatically less than we obtained previously for the harmonic in photobleached waveguides. A figure of merit of η=0.1%/W for second-harmonic generation was obtained with a modest nonlinearity of 3 pm/V at 1607 nm in a 2 mm long waveguide.

Quadratic spatial soliton generation by seeded down conversion of a strong pump beam

Quadratic spatial solitons have been generated during second-harmonic generation under easy-to-achieve conditions and should be pervasive in other second-order nonlinear interactions. One of the more interesting cases is the downconversion process, which is the essence of parametric generators and oscillators. In this investigation, we report on the generation of two-dimensional quadratic spatial solitons (QSS) in a KTP crystal near the degeneracy point for the parametric interaction, i.e., the reverse second-harmonic generation. Here we report on the observation of such solitons in a l-cm-long KTiOPO/sub 4/ crystal where the extraordinarily polarized harmonic field interacts with two fundamental fields with both ordinary and extraordinary components.