No description available.

Chan Tak Shun = 摻鐵鈮酸鋰晶體中相位相關的亮光生伏打空間孤子的相互作用的觀察及光生伏打媒介中高調制深度下所寫的光折變全息圖的理論研究 / 陳德信. / Thesis submitted in: July 2006. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 115-116). / Abstracts in English and Chinese. / Chan Tak Shun = Shan tie ni suan li jing ti zhong xiang wei xiang guan de liang guang sheng fu da kong jian gu zi de xiang hu zuo yong de guan cha ji guang sheng fu da mei jie zhong gao diao zhi shen du xia suo xie de guang zhe bian quan xi tu de li lun yan jiu / Chen Dexin. / Acknowledgements --- p.i / Abstract --- p.ii / Table of Contents --- p.v / Chapter Chapter 1 --- Introduction --- p.1 / References --- p.9 / Chapter Chapter 2 --- Background --- p.10 / Chapter 2.1 --- Space-Charge Field and Band Transport Model --- p.10 / Chapter 2.2 --- Photorefractive Effect and Nonlinear Wave Equation --- p.24 / Chapter 2.3 --- Two-Wave Mixing and Diffraction of Light Incident onto an Index Grating --- p.34 / Chapter 2.4 --- Photorefractive Spatial Solitons --- p.48 / References --- p.60 / Chapter Chapter 3 --- Relevance of interpretation of experimental results of interactions of optical spatial solitons and interaction geometry --- p.62 / Chapter 3.1 --- Introduction --- p.62 / Chapter 3.2 --- Theoretical Model --- p.63 / Chapter 3.3 --- Results and Discussion --- p.65 / Chapter 3.4 --- Conclusions --- p.71 / References --- p.72 / Chapter Chapter 4 --- Experimental investigation of phase-dependent interactions of photovoltaic bright spatial solitons in photorefractive Fe:LiNb03 --- p.75 / Chapter 4.1 --- Introduction --- p.75 / Chapter 4.2 --- Theoretical Background --- p.76 / Chapter 4.3 --- Experiment --- p.83 / Chapter 4.4 --- Results and Discussion --- p.86 / Chapter 4.5 --- Conclusions --- p.90 / References --- p.91 / Chapter Chapter 5 --- Photorefractive hologram writing with high modulation depth in photovoltaic media under different boundary conditions --- p.94 / Chapter 5.1 --- Introduction --- p.94 / Chapter 5.2 --- Theoretical Model and Method --- p.97 / Chapter 5.3 --- Results and Discussion --- p.99 / Chapter 5.4 --- Conclusions --- p.114 / References --- p.115 / Chapter Chapter 6 --- Conclusions and future outlook --- p.117

No description available.

Due to their ability to undergo a refractive index change (.dn) induced by appropriate UV irradiation and thermal development, Photo-Thermo-Refractive (PTR) glass is a candidate material for use in optical applications such as hologram recording, optical data storage, or spectral filters. Although this refractive index modulation (.dn) has been characterized in terms of its optical ramifications, glass scientists are working to understand more clearly the underlying mechanisms associated with the photo-induced crystallization process. Despite numerous difficulties such as the insulating nature of PTR glass, low concentration levels of photosensitive species, nanometer size of the resulting crystalline phase, and reactivity of these crystals to ion and electron beam radiation and temperature, characterization techniques have been successfully used, resulting in an improved understanding of the photo-induced crystallization mechanism. Results of absorption spectroscopy, interferometry, thermal analysis, x-ray diffraction, transmission electron microscopy have allowed detailing a self-consistent mechanism to describe the multiple steps of this complex process. The photo-induced crystallization process has been experimentally verified, step-by-step. Additionally, the evolution of the hetereogenous phase has been quantified. Sodium fluoride precipitates that results from bulk crystallization were determined to be less than 0.25% of the total volume and were within the range of 8 to 14nm in size. Experiments combining interferometry and x-ray diffraction analyses of glasses heterogeneously crystallized at 520°C for 1 hour led to a linear correlation between (.dn) decrement and UV exposure doses. A kinetic study of the heterogeneous crystallization using thermal analysis revealed an exponential decay law linking the activation energy for heterogeneous crystallization as a function of the UV dose for given heat-treatments.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 7 uppsatser.

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007. / Smith, Glenn, Committee Member ; Trebino, Rick, Committee Member ; Adibi, Ali, Committee Chair ; Gaylord, Thomas, Committee Member ; Buck, John, Committee Member.

This work presents recent advances in photorefractive polymer composites towards improved efficiency, speed, persistence of holograms and sensitivity at both visible and near infrared wavelengths. Besides the pure performance characteristics, a thin-device approach is presented to reduce operating voltage of these devices to practical levels and these materials are analyzed in both reflection and transmission geometries.The thin device operating at 1.3kV holds erasable, Bragg holograms with 80% efficiency in addition to its video-rate response time. The transition of hologram state from 'thick' to 'thin' is analyzed in detail. On the near IR portion of spectrum, new photorefractive polymer composites have been developed that enable high performance operation at 845nm and 975nm. Utilizing our novel photorefractive materials we demonstrate large diffraction efficiency in four-wave mixing experiments and video-rate response times. A major step towards achieving submillisecond response times is obtained through recording photorefractive gratings with individual nanosecond pulses at 532nm. At 4 mJ/cm2 illumination, a maximum diffraction efficiency of 56% has been obtained with a build-up time of only 300 microseconds (t1). This fast response enables applications in optical processing requiring frame rates of 100Hz or more. Due to the short duration of the writing pulses, the recording is insensitive to vibrations. Combining molecules that have different frontier orbital energies in a copolymer system and utilizing thermal fixing approach has led to long grating lifetimes of more than several hours. Later, in this dissertation, two low-glass-transition photorefractive polymer composites are investigated in reflection geometry. 60% is diffraction efficiency is observed in 105 micron thick devices of a PVK based composite. The reflection holograms are more sensitive to reading angle and slight birefringence due to the poling of chromophores has proven to cause a Bragg mismatch.

This work presents recent progress in the area of organic photorefractive polymer composites. These materials have been previously shown to be a suitable medium for dynamic holographic displays, with multiple colors and single frame writing times on the order of seconds. However, these materials still require large electric fields and high intensity lasers to function effectively. Recent advancements in improving these areas are discussed, including a review of the history and state-of-the-art in photorefractive polymer composites.The addition of electron traps via low loading of the electron-transporting molecule Alq3 is shown to dramatically improve the diffraction efficiency and reduce the required field. The grating formation also proceeds faster by more than one order of magnitude, leading to an increase in sensitivity by a factor of 3. The dynamics of these materials also show evidence of competing gratings indicative of bipolar charge transport and trapping.The addition of an amorphous polycarbonate (APC) buffer layer is reported to have a similar effect on the steady-state diffraction efficiency, and the further doping with a fullerene derivative (PCBM) allows a 3x increase in the efficiency in the reflection geometry, which is normally poor due to the small grating spacing. These composites reveal the fundamental limits of the reflection geometry, based on the physics of high frequency gratings. A reversal in the direction and increase in the magnitude of the two-beam coupling energy transfer is also observed.The use of interdigitated coplanar electrodes, instead of the standard uniform electrodes in a parallel-plate geometry, is shown to result in large diffraction efficiency with symmetric writing beams due to the increased projection field. The efficiency is similar to that achieved in the standard samples with large slant angles and much better than those geometries typically used in applications, with the benefit that the writing beams do not have to be slanted with respect to the sample normal. Different electrode widths are examined and the trade-offs discussed. This device makes beam injection simpler and allows one to bring the benefits of highly slanted geometries, common to small area setups, to the large-area applications.

by Lee, Kai Kwong Dennis = 一激光束對在光折變晶體中之另一激光束的影響 / 李啓光. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 106-109). / Text in English; abstracts in English and Chinese. / by Lee, Kai Kwong Dennis = Yi ji guang shu dui zai guang zhe bian jing ti zhong zhi ling yi ji guang shu de ying xiang / Li Qiguang. / Acknowledgments --- p.i / Abstract --- p.ii / Table of Content --- p.iv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Theory --- p.4 / Chapter 2.1 --- Two-wave Coupling --- p.4 / Chapter 2.2 --- Four-wave Mixing --- p.10 / Chapter 2.3 --- Fanning --- p.13 / Chapter 2.4 --- Phase-conjugation --- p.16 / Chapter 2.5 --- Spatial Solitons --- p.19 / Chapter Chapter 3 --- "Experiments,Results and Discussion" --- p.26 / Chapter 3.1 --- Measurements of Optically Induced Refractive Index Change --- p.26 / Chapter 3.2 --- Optical Control Experiments --- p.65 / Chapter 3.3 --- Soliton Experiments --- p.80 / Chapter Chapter 4 --- Concluding Remarks and Suggested Further Studies --- p.99 / References --- p.105