Fabrication Of Large-area Photorefractive Photonic Lattices And The Research Of Optical Characteristics

In 1987 E.Yablonovitch and S.John pointed out that the behavior of photons can be changed when propagating in the material with periodically distributed dielectric constant, and termed such material photonic crystal(photonic lattices). Photonic lattices have attracted great attention due to their potential scientific value and wide applications. Different methods have been used to research the structures, theories, fabrication techniques and brand-new physical characters of photonic lattices by the research groups all over the world, and great progresses have been obtained.Currently, it has the disadvantages of long fabrication period and small lattice area of the traditional fabrication techniques. Thus the application of photonic lattices is limited. Recently, light-irradiation methods attract much research interest as a recognized technology for direct, rapid, and cost-effective fabricating of various integrated photorefractive photonic lattices. In this thesis, four methods to form large-area of photorefractive photonic lattices in iron-doped lithium niobate (LiNbO3:Fe) crystals, including optical Fourier transformation method, single-beam scan, the imaging method and the method of interference induction technique are investigated experimentally in detail, the method for measuring the index distributions of light-induced photonic lattices by employing the observation system is investigated both theoretically and experimentally, and photorefractive effect in indium and iron-doped lithium niobate (In:Fe:LiNbO3) crystals induced by near infrared light. In this dissertation, theoretical analysis and experiments on fabrication techniques of large-area photonic lattices are deeply discussed and some valuable results are obtained.The main works are as follows:1. According to the set of equations governing the photorefractive process, photoinduced refractive index change in photorefractive crystals is theoretically analyzed. Based on Mach-Zehnder interferometer setup and LBA-PC make up of the observation system, the principle for measuring light-induced index changes in photorefractive crystals is investigated. And employing observation system for three-dimensional (3D) visualizations of the refractive index modulation is proposed. Additionally, the approach is used for measuring the index changes distributions induced by CW laser at milliwatt in LiNbO3:Fe crystals successfully.2. This dissertation mainly investigates fabricating large-area of photore- fractive photonic lattices in crystals by various structure light irradiation method. Fabrication methods of 1D large-area of photorefractive photonic lattices in crystals employing structure lights formed by single-slice-beam scan and single Mach-Zehnder interferometer are proposed, and the experimental setup of three Mach-Zehnder interferometers for fabrication of the (2+1)D large-area of photorefractive photonic lattices and for observing the refractive index. Multilayer, crossed and square lattice large-area of photonic lattices are experimentally formed in LiNbO3:Fe crystals.3. We successfully fabricate large-area 1D and (2+1)D photonic lattices in LiNbO3:Fe crystals of different thickness by diverse light induced techniques. The influences of polarization states, irradiation time, doping density, and thickness on fabricating photonic lattices and the refractive index modulation are analyzed. The optimized parameters of fabricating large-area and short period structure photonic lattices are presented, and the questions in experimentation need attentively are narrated in detail.4. For the one-dimensional cases of photonic lattices, relations between the duty cycle of holograph and the refractive index modulation are obtained.5. Photorefractive effect is experimentally formed in indium and iron-doped lithium niobate crystals induced by low-power near infrared light is obtained. The refractive index change in photorefractive crystals induced by low-power near infrared light are theoretically analyzed and studied experimentally, be differ from visible light illuminating. The influences of polarization states, intensity ratio and irradiation time with the refractive index changes are investigated experimentally. Refractive index changes and physical mechanism of photorefractive effect in In:Fe:LiNbO3 induced by low-power near infrared light is theoretically analyzed.