Photorefractive materials and effects for photonics

This special issue of Journal of Optics A: Pure and Applied Optics is devoted to a mature field of nonlinear optics: photorefractive materials and effects for photonics. Photorefractivity was discovered long time ago by A Ashkin et al in 1966 and since then much work has been performed to characterize the phenomenon and to apply it. Nevertheless, research in this field remain very active and productive, in both basic and applied directions. Some leading groups worldwide present their most up-to-date investigations of photorefractive materials and effects, as well as their applications in photonics. Thus, the papers in this issue report new results in three directions: photorefractive material researches, wave propagation (particularly solitons) through these nonlinear optical materials, and various applications and devices using photorefractive effects. The challenging goal of photorefractive material research is to find sensitive and fast materials for information transmission and processing. P M Johansen studies the fundamental problem of space--charge field formation in photorefractives. V Marinova et al show that light-induced properties of Ru-doped Bi 12 TiO 20 (BTO) crystals has an extended sensitivity in the near infrared region. H A Al-Attar and O Taqatqa introduce a new photorefractive polymer composite for their interesting properties for optical data storage. R Ramos-Garcia et al perform measurements of absorption coefficient and refractive index changes in photorefractive quantum wells of GaAs. A Radoua et al characterize by two-wave mixing the photorefractive Ba 0.77 Ca 0.23 TiO 3 :Rh crystals (BCT) at 1.06 μm, and M K Balakirev et al study the photorefractive effect upon all optical poling of glass. Wave propagation and solitons are intensively studied in photorefractive crystals due to the possibility of obtaining steady-state spatial solitons, dynamic waveguiding and soliton interactions at low laser intensity. W Ramadan et al introduce a new procedure to obtain stationary self-confined beams at non-absorbed wavelengths in Bi 12 SiO 20 (BSO). Two groups, C Weilnau and C Denz and Z Chen et al , investigate photorefractive solitons using partially coherent light beams. Waveguiding and interactions in photorefractive soliton arrays are demonstrated by R Delgado Macuil and M D Iturbe Castillo and by D Träger et al . V Matusevich et al show some aspects of fanning, self-focusing and self-defocusing in a photorefractive BCT crystal. Applications and devices are developing in hologram recording and storage, image processing, interferometry and optical phase conjugation in photorefractive materials. G Berger et al record non-volatile volume holograms in bismuth tellurite crystals. I de Oliveira and J Frejlich perform diffraction efficiency measurement in photorefractive thick volume holograms. Holography with photorefractive multiple quantum well devices is used by C Dunsby et al in high-speed wide-field coherence-gated imaging. A photorefractive fringe-locked running hologram is analysed by M C Barbosa and J Frejlich in three-dimensional space. Detection of small in-plane vibrations using the polarization self-modulation effect in GaP is performed by Y Iida et al . E Weidner et al design an interferometric camera with a wavefront buffer memory using a photorefractive crystal as the active medium. R Nicolaus et al investigate and optimize a pulsed ultraviolet image amplifier within a micro-marking system. C Gu et al apply unconventional photorefractive materials in fibre optic devices. Photorefractive phase conjugate mirrors are used by T Omatsu et al to obtain multi-watt picosecond pulses from a diode-pumped Nd:YVO4 amplifier with a diffraction-limited spatial profile, and V M Petrov et al design optical on-line controllable filters based on photorefractive crystals. We hope that this special issue of Journal of Optics A: Pure and Applied Optics will reflect the intense activity in the field of photorefractivity and will demonstrate to readers some of the actual directions of research in these topics. We express our full appreciation to the authors and we would like to thank the paper reviewers for their important role in the paper selection process. We acknowledge the Publisher, Claire Bedrock, and the technical staff of the journal for their support, dedication and energy, which made feasible this special issue.