Alex K.Y. Jen

Hyper-Rayleigh scattering studies of first order hyperpolarizability of tricyanovinylthiophene derivatives in solution

First order hyperpolarizabilities, β, for donor–acceptor substituted heteroaromatic compounds are measured by the hyper‐Rayleigh scattering technique. Hyper‐Rayleigh scattering utilizes the mechanism of number density fluctuations and enables the second harmonic generation signal of nonlinear optical chromophores to be generated as scattered light. Effects of substituting different electron donating groups to the parent heteroaromatic compounds and different solvents on the hyperpolarizability is investigated using this technique.

Rhodanine-methine as π-electron acceptor in second-order nonlinear optical chromophores

Abstract This study describes the synthesis, electronic absorption and second-order nonlinear optical properties of a series of new dialkylamino electron-donor and rhodanine-methine electron-acceptor substituted conjugated compounds. EFISH studies indicate that rhodanine-methine acceptor offers substantially enhanced molecular nonlinear properties (βμ) compared to the well known and commonly used nitro acceptor.

Development of highly active, thermally stable chromophores and polymers for electro-optic applications

We have developed two classes of highly efficient and thermally stable nonlinear optical chromophores using fused-thiophene and bithiophene as conjugating units. Experimental studies indicate that the use of fused-thiophene or bithiophene as a (pi) conjugating bridge provides an excellent tradeoff between nonlinearity and thermal stability. In addition to the chromophore developments, we have employed new synthetic methodologies to obtain thermally stable poled polyimides.

New developments in thermally stable second order nonlinear optical chromophores and electro-optic polymers

A new class of thermally and chemically stable donor-acceptor substituted thiophenes is presented. It is shown that exceptionally large electro-optic activity (as high as 30 pm/V at 1.3 micrometers ) can be achieved by doping/covalently bonding highly efficient trycyanovinylthiophenes into high temperature polymers such as polymidies and polyquinolines. Monitoring the long-term stability of electro-optic activity at temperatures above 100 degrees C has revealed that the covalent bonding approach is quite superior to the guest-host approach in polymide as well as polyquinoline based materials.

Progress on heteroaromatic chromophores in high-temperature polymers for electro-optic applications

We have developed several classes of thermally stable nonlinear optical chromophores based on the combination of efficient thiophene conjugating units and novel electron-donating and electron-accepting functional groups. The incorporation of these chromophores into high temperature polymers produces high linear electro-optic coefficients and long-term thermal stability at elevated temperatures. Active Mach-Zehnder interferometers with a V(pi) phase shift of 50 volts and low attenuation (< 2 dB/cm) were fabricated. Thermal baking of the poled device demonstrated no change in activity after 30 minutes at 230 degree(s)C.

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].

High-performance electro-optic polymers and their applications in high-speed electro-optic switches and modulators

Recent progress in the development and application of highly active, highly thermally stable, and low optical loss electro-optic polymers is presented. Nonlinear optical chromophores with large molecular nonlinearities and high thermal and chemical stabilities are covalently attached to optical grade polyimides to form side-chain polymers with electro-optic coefficients as high as 45 pm/V and lifetime over 106 hours at 100 degrees Celsius. Cladding polymers with matching optical, mechanical, and electrical properties have been formulated and processed. Using a novel trench- and-fill process, integrated high speed electro-optic switches and modulators have been fabricated and tested.