Yongming Cai

Ketene dithioacetal as a π-electron donor in second-order nonlinear optical chromophores

It is shown experimentally that the ketene dithioacetal group is very effective as an electron-donating group in the design and synthesis of thermally stable and efficient second-order nonlinear optical chromophores.

Highly active and thermally stable nonlinear optical polymers for electro-optical applications

Poled guest-host polyquinoline thin films are shown to demonstrate both exceptionally large electro-optic activity and long-term thermal stability. After an initial drop from 45 pm/V to 26 pm/V in the first 100 hours, the electro-optic coefficient r33 at 26 pm/V remained for more than 2000 hours.

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.

Achieving excellent tradeoffs among optical, chemical and thermal properties in second-order nonlinear optical chromophores

A new class of second-order nonlinear optical chromophores resulting from the replacement of the most reactive CN group in tricyanovinylthiophene derivatives with aryl units, are designed and synthesized.

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.

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.

Design and synthesis of thermally stable side-chain polyimides for second-order nonlinear optical applications

Novel Mitsunobu and tricyanovinylation reactions have been employed to incorporate efficient nonlinear optical chromophores as side-chains into aromatic polyimides resulting in high electro-optic activity and long-term alignment stability at 100 °C for more than 500 h.

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.

Thermally stable nonlinear optical polyimides: synthesis and electro-optic properties

A facile synthetic method has been developed to incorporate efficient nonlinear optical chromophores as side-chains into high temperature polyimides resulting in high electro-optic activity and long-term thermal stability at 90 °C for over one month.