Temporal Behavior of the Intensity-Dependent Absorption in Photorefractive BaTiO3
Abstract
Since the observation of an anomalous behavior of barium titanate in a two-beam coupling experiment by Klein and Valley and the observation of asymmetric coupling gain coefficients with respect to the sense of the c axis, we have reported that the anomalous behavior and the nonsymmetric behavior of the coupling gain may be due to the intensity-dependent absorption coefficient. Models have been proposed to explain the anomalous behavior, but the exact source of the anomaly is not well understood at present. We have shown that the intensity-dependent absorption is consistent with the presence of secondary centers. These are intermediate-level traps that are highly ionized at room temperature but can compete for free carriers generated by photoexcitation of the deep traps. The secondary centers then become populated and are available for additional absorption and photorefraction. Our mathematical analysis shows that this model predicts both an intensity-dependent absorption and an intensity-dependent photorefractive effect (PRE). We report measurements of response time for the intensity-dependent absorption in a single BaTiO3 crystal under conditions in which no photorefractive effect can be observed. The speed of response is found to increase with increasing intensity but in a sublinear fashion similar to that observed for photorefractive decay. This experiment provides unambiguous evidence for the intensity-dependent absorption in BaTiO3 crystals.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1988
- Accession Number
- ADA198105
Entities
People
- Andy Motes
- George Brost
- Jim Rotge
- Jin J. Kim
Organizations
- Air Force Research Laboratory