The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Switches, and Actuators Masahiro Irie,*,† Tuyoshi Fukaminato,‡ Kenji Matsuda, and Seiya Kobatake †Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro 3-34-1, Toshima-ku, Tokyo 171-8501, Japan ‡Research Institute for Electronic Science, Hokkaido University, N20, W10, Kita-ku, Sapporo 001-0020, Japan Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan Department of Applied Chemistry, Graduate School of Engineering, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan

Photochromism of Diarylethene Molecules and Crystals: Memories, Switches, and Actuators

Optical resonance and two-level atoms

5.3.2. Traps and Grating Dark Decay 3288 5.3.3. Other Concerns 3288 6. New Photorefractive Materials 3289 6.1. Polymer Composites 3289 6.2. Organic Amorphous Glasses 3292 6.3. Fully Functionalized Polymers 3294 6.4. Polymer-Dispersed Liquid Crystals 3295 6.5. Other Liquid Crystal-Containing Materials 3296 6.6. Near-Infrared-Sensitive Materials 3297 6.7. Other Materials Directions 3298 6.7.1. Hybrid Organic−Inorganic Composites and Glasses 3298

Organic photorefractives: mechanisms, materials, and applications.

Preface 1. Wave Theory of Optical Waveguides 2. Planar Optical Waveguides 3. Optical Fibers 4. Couple Mode Theory 5. Nonlinear Optical Effects in Optical Fibers 6. Finite Element Method 7. Beam Propagation Method 8. Staircase Concatention Method 9. Planar Lightwave Circuits 10. Theorems and Formulas Appendix

Fundamentals of optical waveguides

The coupled wave theory of Kogelnik [H. Kogelnik, Bell Syst. Tech. J. 48, 2909 (1969)] is extended to the case of moderately absorbing thick anisotropic materials with grating vector and medium boundaries arbitrarily oriented with respect to the main axes of the optical indicatrix. Dielectric and absorption modulation with common grating vector and of arbitrary relative phase shift is considered. Solutions for the wave amplitudes, diffraction efficiencies, and angular mismatch sensitivities are given in transmission and reflection geometries. The main difference of the new results with respect to the expressions valid for isotropic media arise due to the walk-off between the wave-front and energy propagation directions. The difference is particularly important in materials with large birefringence, such as organic crystals, ordered polymers, and liquid crystalline cells. The special case of Bragg diffraction and two-beam coupling at holograms recorded in optically inactive photorefractive crystals is analyzed in detail. It is found that the two-beam coupling gain is influenced substantially by an absorption anisotropy.

Light diffraction at mixed phase and absorption gratings in anisotropic media for arbitrary geometries

Electro-optical properties of Sn2P2S6

The photorefractive properties of stoichiometric LiNbO3 crystals with a small number of defect densities grown by the double-crucible Czochralski method are investigated and compared with the defect densities of commercially available congruent Fe-doped LiNbO3 crystals. Two-wave-mixing experiments show that novel stoichiometric crystals exhibit larger photorefractive gain and considerably faster response times than congruent ones. The results indicate that the nonstoichiometry defect control of photorefractive crystals is of key importance for the improvement of their properties.

Photorefractive properties of iron-doped stoichiometric lithium niobate

The photorefractive properties of Sn2P2S6 crystals doped with Te and Sb in the near-infrared wavelength range up to 1064 nm are reported. The main photorefractive parameters, i.e., two-wave mixing gain, effective electro-optic coefficient, diffusion length, concentration of traps, and response time, are compared with conventional nominally pure Sn2P2S6. Te-doped Sn2P2S6 shows the fastest response with the smallest decrease of the photorefractive efficiency with increasing wavelength in the near infrared. Sb doping, on the other hand, inhibits photorefraction in the near infrared. Sn2P2S6:Te and Sn2P2S6:Sb crystals both show a high two-wave mixing gain Γ at 633 nm, and 10 and 20 cm−1. Te-doped Sn2P2S6 shows a photorefractive gain of 4.5 cm−1 at 1064 nm. Response times at 1064 nm of 20 ms have been measured for the intensity 6 W/cm2, which is 2 orders of magnitude shorter than in Rh-doped BaTiO3.

Tailoring of infrared photorefractive properties of Sn 2 P 2 S 6 crystals by Te and Sb doping

We demonstrate holographic fixing by means of a thermal cycling procedure in pure and doped photorefractive KNbO3 crystals. At elevated temperatures (70–100°C) the photoinduced grating is compensated for by a secondary grating that is formed by charge carriers whose thermal activation energy is ~1.0 eV. The secondary carriers are stable at room temperature and form the fixed grating after cooling the crystal. They are believed to be represented by ions or ion vacancies. By using our fixing mechanisms the holographic storage time in KNbO3 can be increased by a factor of 106.

Germano Montemezzani

Papers

Light diffraction at mixed phase and absorption gratings in anisotropic media for arbitrary geometries

Electro-optical properties of Sn2P2S6

Photorefractive properties of iron-doped stoichiometric lithium niobate

Tailoring of infrared photorefractive properties of Sn 2 P 2 S 6 crystals by Te and Sb doping

Thermal hologram fixing in pure and doped KNbO 3 crystals