title: Fixed holograms in iron-doped lithium niobate: simultaneous self-stabilized recording and compensation.
abstract: We analyze the mechanisms leading to a highly diffractive fixed hologram in photorefractive Fe-doped lithium niobate crystals by simultaneous self-stabilized holographic recording and compensation at moderately high temperatures. We show that a partially compensated running hologram is produced during recording under this condition and discuss the performance of the process in terms of the operating temperature, the degree of oxidation ([Fe(3+)]/[Fe(2+)] ratio) of the sample, and the effect of the absorption grating arising from the spatial modulation of the Fe(2+) concentration produced during photorefractive recording. We experimentally measure the evolution of the uncompensated remaining hologram during recording and the evolution of the diffraction efficiency of the fixed hologram during white-light development and show that the maximum fixed grating modulation to be achieved is roughly limited by Fe-dopant saturation. A reproducible eta approximately 66% efficiency fixed grating was obtained on a sample exhibiting an otherwise maximum fixed eta approximately 3% when using the classical three-step (recording at room temperature--compensating at high temperature--developing at room temperature) process.
authors.affiliation: Laboratório de Optica IFGW-UNICAMP, Universidade Estadual de Campinas, Campinas, Sao Paulo, Brazil. frejlich@ifi.unicamp.br
authors.forename: Jaime
authors.initials: J
authors.lastname: Frejlich
authors.forename: Ivan
authors.initials: I
authors.lastname: de Oliveira
authors.forename: Luis
authors.initials: L
authors.lastname: Arizmendi
authors.forename: Mercedes
authors.initials: M
authors.lastname: Carrascosa