In this thesis, we fabricated the 2D photonic crystal and modified 1D photonic crystal microcavity on the InGaAs/GaAs substrate by E-beam lithography. The wafer are grown by molecular beam epitaxy (MBE) on GaAs substrate. The active layer consists of six InGaAs quantum wells at 1050nm emission wavelength. For the 1D photonic crystal microcavity (DBR laser),we changed the cavity shape and length to match the mode of light in the cavity. It can increase the reflectivity of the laser. In our simulations, we scanned different cavity length and found the corresponding data. We designed two and three pairs of DBRs formed on the edge of laser cavity, respectively. The cavity length is 121µm and the mirror width is 230nm and the air gap is 263nm. For the 2D photonic crystal (2DPC) microcavity, a triangular array of air columns was adopted. The lattice constant and air columns radius are 742nm and 304nm, respectively. The TE modes photonic band gap of this structure are corresponding to wavelength range in 1026nm ~ 1089nm. We placed single defect in the 2DPCs to form 2DPC microcavities and the corresponding defect modes are 1051.58nm¡B1053.39nm and 1054.87nm. In addition, we reduced the air columns around the cavity and simulated the photonic bandgap and fabricated the devices by E-beam lithography and deep dry etching process.

In this thesis, we fabricated the 2D photonic crystal microcavity and laterally coupled distributed feedback laser on InGaAs/InAlGaAs wafers by E-beam lithography. We also fabricated the 2D photonic crystal microcavity on the InGaAs/GaAs substrate at 980nm emission wavelength. The wafer are grown by molecular beam epitaxy (MBE). For the laterally coupled distributed feedback laser (LC-DFB laser) , we changed the grating shape and length to form proper grating, and it will make constructive diffraction and coupling. We design the mirror width is 180.55nm and the air gap is 541.65nm. For the 2D photonic crystal (2DPC) microcavity, a triangular array of air columns was adopted. The lattice constant and air columns radius are 1139nm and 456nm, respectively. The TE modes photonic band gap of this structure are corresponding to wavelength range in 1522.72nm~1617.89nm. We placed single defect in the 2DPCs to form 2DPC microcavities and the corresponding defect modes are 1549.23nm and 1550.08nm. We have simulated the photonic bandgap and fabricated the devices by E-beam lithography and deep dry etching process. Also, we can use the same method to fabricate 980nm photonic crystal.

Due to its easy growth, higher nonlinear coefficients, and better optical characteristics, LiNbO3 is broadly used as nonlinear crystal in laser system and wavelength converter in optical communication systems. In this thesis, we discuss the use of LHPG method to grow periodically poled LiNbO3 crystal fiber without metallic patterns. During the growth, micro-swing is managed to assist poling process, simultaneously we can understand and simulate the electric-field induced current. Using the relation between current waveform and micro-swing amplitude, we can quantify the micro-swing amplitude, and establish feedback control to enhance the stability during crystal fiber growth process. The achieved internal SHG conversion efficiency is 14.8 % with a quasi-phase matched period of 15.45 £gm. Besides promoting process stability and improving uniformity of domain inversion period, it is our hope that the relation between domain inversion and measured induced current can be clarified in the future. Due to the low Curie temperature of LiTaO3, it is expected that our experience on LiNbO3 can facilitate the development of periodic poling on LiTaO3.

We propose to develop a voltage-controllable multi-guide directional coupler in a planar nematic liquid crystal cell. The ITO grating-like electrodes are fabricated by the etching technique, and the director of liquid crystals will be aligned to the direction of applied electric field. Owing to the uniaxial property of liquid crystals, the difference of refractive index between two neighboring channels is increased with the applied voltage. Therefore, the coupling efficiency among grating-like multi-guide is also increased with the applied voltage. By using the combination of microscope and CCD system, the dynamic coupling can be observed under the distribution of grating-like electric field. The propagation of light in each channel can be selected by the controllable voltage between the electrodes of the individual channel. The intensity distribution of coupling in the transverse direction can be obtained by analyzing the image captured from the microscope and CCD system.

We hope to achieve the goal of improving molecule nature of the liquid crystal by change the functional group or the symmetry of the molecule. In the thesis, the derivatives of dibenzophenazine are synthesized and their mesogenic properties are investigated. Polarised optical microscopy (POM) and differential scanning calorimetry (DSC) studies show all these compounds to exhibit a very wide mesophase range. These mesophases are identified as columnar hexagonal phases by X-ray diffraction (XRD).

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The rapid developments in optical and electronic technologies have accelerated developments of solid state laser technology. The diode-pumped solid state laser has the merits of the diode laser, such as compactness, low cost, and the merits of the solid state laser, such as high laser quality, high conversion efficiency, long lifetime, and simple structure. There use in laser applications is very cost-effective in terms of material consumption, which is typically one-thousandth that of bulk material. In addition, heat dissipation in the gain medium can be significantly alleviated because highly heat-conductive material can be applied to the circumference of the crystal fiber. So, it was applicated in electronics, communication and medicine widely. The laser-heated pedestal growth (LHPG) method is now a well-established technique for the growth of single-crystal fibers. It is crucible free and can therefore produce high-purity, low-defect-density single crystals. Interface loss is one of the dominant factors that reduce the efficiency of crystal fiber lasers, although cladding with a dielectric coating or in-diffusion of the gain core has been utilized to suppress this interface loss. Using a gradient-index Nd:YAG crystal fiber with peak Nd concentration up to 1.6-atm.%, we recently demonstrated a laser power of 145 mW and slope efficiency 28.9%. Peak Nd concentration up to 3.6-atm.% Nd:YAG crystal fiber with a 20-um core was grown, which could eliminate the interface loss and enhance the efficiency of crystal fiber lasers to be compatible with bulk solid-state lasers.

Optical measurement is a very important science in present times. Generally, optical interference is applied in precise measuring. In this thesis, we use the opto-electric properties of liquid-crystal layers and the phase-shifting shearing interferometer will be applied. Clear patterns should be figured when measuring optical properties traditional interferometers. A new interferometer called phase-shifting shearing interferometer was developed recently. It is not necessary to appear clear patterns in measurements. In application to this interferometer, the phase information got by way of shifting the reference lens that can control phase differences. Phase controlled in thus method is mostly by the step motor or the PZT installation. Now we replace this installation by liquid-crystal layers since the accuracy of liquid-crystal layers controlled by voltage is better than the mechanical installation. The measuring precision is improved wide. In this paper, we study the optical properties under the application both DC and AC voltage to a series of thickness of the liquid-crystal layer, and the suitable condition of liquid-crystal layers to apply to the phase-shifting shearing interferometer.

Abstract There are three parts in this paper. The first, we study the mechanism of soliton in nematic liquid crystal (NLC), molecules of NLC will be rotated easily by optical field while we apply an external electric field. Then the effective refraction index is changed. The light beam in NLC will create spatial soliton by producing the effect of self-focusing to balance the diffraction. Second, we study the interaction between solitons. One soliton will create a potential well of refraction index. The other one will be attracted in the potential well. These two solitons propagate in the form of spiral, if the separated distance and the angle are suitable. And the third, we observe the phenomenon with probe beam in the path of soliton. The path of the soliton forms a channel like a wave guide. The probe beam insert into the path of the soliton with different angles. The probe beam collides with the soliton in the proper range of angles will follow its path.

Crystals are natural phenomena that exhibit high degrees of order, symmetry, and recursion. They naturally form interesting and inspiring geometric shapes. This thesis provides geometric modeling techniques for creating shapes with crystallike geometry. The tiered extrusion method, along with a face grouping technique, simplifies the creation of complex, intricate faceted shapes. In combination with remeshing, these methods provide the capability to generate geometric shapes exhibiting planar faces, symmetry, and fractal geometry. The techniques have also been implemented in software, as a proof of concept. They are used in an interactive geometric modeling system, in which users can use these techniques to create crystal-like shapes. The crystal-like modeling operations are shown to successfully create beautiful geometric shapes. The methods improve upon traditional modeling capabilities, providing an easier way to create crystal-like geometric shapes.