1. Alex Sushkov Phys208 Oct 27 2004 Photorefractive effects and their applications

2. The effect Spatial variation of light intensity inside a photorefractive crystal Excitation of e - into the conduction band e - diffusion or drift Space-charge E-field  n due to Pockels effect Photorefraction

3. The discovery

4. The materials LiNbO 3, LiTaO 3, BaTiO 3, KNbO 3, KH 2 PO 4, GaAs, …, organic and polymeric materials

5. Photorefraction – the easy way

6. Two-wave mixing

7. Four-wave mixing

8. Photorefraction+Cavity Photorefractive crystal as an amplifying medium Phase conjugation

9. Laser locking and phase conjugation

10. Holograms

11. Holographic data storage 20000 holograms in a single LiNbO 3 crystal have been demonstrated. Diffraction limit on storage capacity: n 3 V/ 3  10 Tb/cm 3.

12. Holographic data storage: I/O rates Access time: 100  s Readout rate: 1-10 Gbits/s Writing time: 10 seconds/hologram, 10Mbit/s

13. Holographic data manipulation

14. Holographic image recognition

15. Why do we still have CDs and laptops? High/low carrier mobility tradeoff: writing speed vs storage time (semiconductors/ferroelectrics). Beam fanning. Self-diffraction and other dynamic effects during hologram recording and reading. New materials being developed: photopolymers and photosensitive glasses.

16. References M. P. Petrov, S. I. Stepanov, and A. V. Homenko, Photorefractive Crystals in Coherent Optics, Nauka, St. Petersburg, 1992. H. M. Smith, Principles of Holography, Wiley, New York, 1975. G. S. He, S. H. Liu, Physics of Nonlinear Optics, World Scientific, Singapore, 1999.