K. Y. Wong

Novel push-pull thiophenes for second order nonlinear optical applications

Abstract Second order molecular nonlinear optical properties of push-pull stillbenes can be substantially increased by replacing benzene with thiophene rings. Synthesis and nonlinear optical properties of several dialkylamino-nitro substituted thiopene based stilbenes are presented.

Theoretical and experimental studies of the molecular second order nonlinear optical responses of heteroaromatic compounds

We present theoretical and experimental studies of the molecular second order nonlinear optical responses of donor–acceptor substituted conjugated compounds which consist of heteroaromatic moieties in place of the traditional benzenoid moieties. Electric‐field‐induced second harmonic generation measurement at a fundamental wavelength of 1.907 μm demonstrated a twofold increase of the off‐resonant molecular hyperpolarizability of a heteroaromatic compound compared to its benzenoid counterpart. Results of theoretical calculations based on ab initio scheme are in good agreement with the experimental results.

Functionalized thiophenes: second-order nonlinear optical materials

It is shown experimentally that the complete replacement of benzene rings with thiophene rings in a donor–acceptor substituted stilbene significantly enhances its second-order nonlinear optical hyperpolarizability (β); results obtained with a series of thiophene-substituted donor–acceptor compounds with different conjugation lengths reveal a power law dependence of βµ on the molecular conjugation length.

Dramatically enhanced second-order nonlinear optical susceptibilities in tricyanovinylthiophene derivatives

Experimentally measured second-order nonlinear hyperpolarizability (βµ) data for a new series of donor-acceptor conjugated compounds containing tricyanovinyl acceptors and thiophene conjugating units, reveal that this combination results in a dramatic enhancement (αµ= 6000–9000 × 10–48 esu) of their molecular nonlinearity.

Thermally stable poled polymers: highly efficient heteroaromatic chromophores in high temperature polymides

In this paper, we report our recent developments in achieving thermally stable polyimides that possess large second order nonlinear optical activity. We have developed several classes of novel chromophores based on the combination of efficient thiophene conjugating units and novel electron-donating and electron-accepting functional groups. Through these developments, we have synthesized chromophores that possess nonresonant βμ values as high as 9100 × 10-48 esu measured at 1.9 µm. These chromophores also possess improved thermal and chemical stabilities. The incorporation of these chromophores in high temperature polyimides produces E-0 materials with high linear electro-optic coefficients (in excess of 15 μm/V at 1.3 μm) and long-term temporal stability at an elevated temperature of 150°C for more than 750 h.

Heteroaromatics: Exceptional Materials for Second Order Nonlinear Optical Applications

New classes of nonlinear optical molecules were synthesized and characterized. It is shown experimentally that molecules with heteroaromatic π-electron systems exhibit exceptional second order nonlinear optical response and good solubility. Measurement of the nonlinear optical properties of molecules containing heteroaromatic moieties with different length scale reveals a power law dependence of Bμ on the number of π-electrons. Also, the effects of two nitro groups as electron acceptors on the aromatic ring are discussed.

Thermally Stable Poled Polymers: Highly Efficient Heteroaromatic Chromophores In High Temperature Polyimides

In this paper, we report our recent developments in achieving thermally stable polyimides that possess large second order nonlinear optical activity. We have developed several classes of novel chromophores based on the combination of efficient thiophene conjugating units and novel electron-donating and electron-accepting functional groups. Through these developments, we have synthesized chromophores that possess non-resonant βμ values as high as 9,100 × 10 −48 esu measured at 1.9 μm. These chromophores also possess improved thermal and chemical stabilities. The incorporation of these chromophores in high temperature polyimides produces E-O Materials with high linear electro-optic coefficients (in excess of 15 pm/V at 1.3 μm) and long-term temporal stability at an elevated temperature of 150°C for more than 800 hours.

Experimental and theoretical studies of heterocyclic nonlinear optical materials

Second order nonlinear optically active heterocyclic compounds with extended length-scale were synthesized and their nonlinear optical properties were characterized by EFISH measurements. The results from the study of two series of heterocyclic compounds with different electron acceptors reveal a power-law dependence of (Beta) (mu) on length, and in both series similar power-law exponent of approximately 2 are observed. Results of a theoretical model calculation are in qualitative agreement with the experimental results.

Optimization of second-order nonlinear optical properties of push-pull conjugated chromophores using heteroaromatics

In continuation of our studies on donor-acceptor substituted heteroaromatic nonlinear optical chromophores, we have developed a new series of thiophene derivatives containing dialkylamino electron-donor and tricyanovinyl electron-acceptor substituents. EFISH measurements indicate that the combination of tricyanovinyl acceptors and thiophene conjugating moieties yields dramatically enhanced molecular nonlinear properties [(beta) (mu) (at (lambda) equals 1.907 micrometers ) equals 6000 - 9100 X 10-48 esu].