Abstract
We report recent improvements in the photorefractive performance of liquid crystalline thin film composites containing electron donor and acceptor molecules. The improvements primarily result from optimization of the exothermicity of the intermolecular charge transfer reaction and improvement of the diffusion characteristics of the photogenerated ions. Photorefractivity resulting from intramolecular charge transfer dopants is also discussed.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 901-902 |
| Number of pages | 2 |
| Journal | Synthetic Metals |
| Volume | 84 |
| Issue number | 1-3 |
| DOIs | |
| State | Published - Jan 1997 |
Funding
Photorefractive materials have received a great deal of attention for optical signal processing applications [l]. The recent development of photorefractive polymers which are more cost efficient and easier to prepare and modify than their inorganic counterparts has fueled a recent surge of research in this area [2,3]. Through gradual improvements of the charge transport and electrooptic characteristics of the polymers, the photorefractive gain of these materials now exceeds those of the inorganic crystals currently available. The newest organic photorefractive material is the liquid crystalline thin film [4-71. The photorefractivity of nematic liquid crystals is derived from the reorientation of the birefringent rod-like molecules in the photoinduced space-charge field which subsequently modulates the index of refraction of the sample. Researchers have utilized this effect in photorefractive polymers by decreasing the glass transition, thereby permitting orientation of the nonlinear optical chromophores. In fact, researchers recently reported that 80% of the observed photorefractivity of their polymer was due to the orientational (or quadratic) electrooptical effect [3]. Since liquid crystals are composed entirely of the birefringent chromophore, as opposed to a fraction within polymer composites, liquid crystals represent an excellent opportunity to improve the photorefractive gain performance of organic materials. Furthermore, liquid crystals do not require large electric fields to align the non-linear optical chromophores (up to 900kV/cm in some polymers) and only a 1SV battery is required to induce directional charge transport. We recently reported large photorefractive gains in nematic liquid crystals doped with electron donor and acceptor molecules[6]. In fact, the photorefractive gain was superior to the best photorefractive polymers available. This was accomplished l We gratefully acknowledge support from the Office of Computational and Technological Research, Division of Advanced Energy Projects, U.S. Department of Energy, under contract W-31-109-ENG-38.
Keywords
- Non-Linear optical methods
- Photoconductivity
- Semiconductor films
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry
