The absence of appropriate media to cultivate photons efficiently at the micro or nano scale has hindered taking the full advantage of processing information with light. The proposal of such a medium for light, known as photonic crystals (PCs)--multi-dimensional artificially periodic dielectric media--brings the possibility of a revolution in communications and sensing much closer. In such media, one can manipulate light at a scale on the order of the wavelength or even shorter. Applications of PCs other than in communication include bio-sensing because of the peculiar properties of PCs such as the capability of enhance field-matter interaction and control over the group velocity. As a result, PC waveguide (PCW) structures are of interest and it is expected that PC sensors offer the feasibility of multi-analyte and compact sensing schemes as well as the ability of the detection of small absolute analyte quantities (nanoliters) and low-concentration samples (picomoles), which may be advantages over conventional approaches such as fiber optic and slab waveguide sensors. Depending on the nature of the analyte, either dispersive or absorptive sensing schemes may be implemented. Light propagation is controlled fully only with 3D PCs. One of the problems arising due to reducing the dimension to 2D is that PCs become strongly polarization sensitive. In many cases, one wants to implement polarization insensitive devices such that the PC provides a full band gap for all polarizations. To address this problem, a novel type of PC called annular PC is proposed and analyzed. The capability of tuning the TE and TM polarizations independently within the same structure provides great flexibility to produce polarization-independent or polarization-dependent devices as desired. PCW bends are expected to be the essential building blocks of photonic integrated circuits. Sharp corners having small radii of curvature can be obtained. To enhance the low-loss and narrow-band transmission through these bends, PC heterostructures waveguide concept is introduced. We show that in PCWs formed by joining different types of PCs in a single structure, light can flow around extremely sharp bends in ways that are not possible using conventional PCWs based on a single type of PC.

This thesis reports on a new design of photonic crystal waveguides (PCWs) to achieve large guiding bandwidth, linear dispersion, single-mode behavior, good coupling efficiency to dielectric waveguides, and small loss. The design is based on using the linear dispersion region of one PCW in the photonic bandgap (PBG) of another PCW. While perturbing the period can result in a PCW with linear dispersion and large guiding bandwidth, it introduces an odd mode at those frequencies, as well. By using another perturbation scheme, it is shown that single-mode behavior can also be achieved. The linear dispersion of these waveguides and their operation at lower frequencies of the PBG, where the density of states of radiation modes is smaller, gives rise to very small loss coefficients as verified experimentally. Full characterization of a waveguide requires the measurement of not only the transmission coefficient, but also the dispersion and spectral phase. We have developed a real-time characterization technique based on spectral interferometry with femtosecond laser pulses at optical communication wavelengths to measure the spectral phase of waveguides. This haracterization technique can be used to study fast dynamics in timevarying structures and makes the alignment easy.

This study presents an optically switchable band gap of a 3D photonic crystal that is based on an azobenzene-doped liquid crystal blue phase. The trans-cis photoisomerization of azobenzene was induced by irradiation using 473nm light, and caused the deformation of the cubic unit cell of the blue phase and a shift in the photonic band gap. The fast back-isomerization of azobenzene was induced by irradiation with 532nm light. The crystalline structure was verified using a Kossel diffraction diagram. An optically addressable blue phase display, based on Bragg reflection from the photonic band gap, is also demonstrated. It can be written, erased, and rewritten repeatedly and exhibits a bright saturated color.

A long period fiber grating (LPFG) is formed by inducing the periodic refractive index variation along a fiber. A lot of work has been done to fabricate the LPFGs in the photonic crystal fibers (PCFs) to function as all-fiber band-rejection filters, interferometers, and sensing applications. In this thesis, we propose a novel LPFG based on the gel-filled PCF. The PCF filled with the UV gel was exposed to the high-intensity UV light through the mask. The periodic index variation is formed along the fiber in the cladding region, resulting in the LPFG. By measuring the propagation losses of our LPFG, three spectral dips in the transmission bands are observed at 872 nm, 1309 nm, and 1418 nm as the grating period is 600 £gm, which indicates the mode coupling from the fundamental core mode to the higher order modes (HOMs) of the gel-filled PCFs. By using a full-vector finite-difference frequency-domain (FDFD) method, we numerically calculate the phase match condition for our LPFGs. The calculated resonant wavelengths are 875 nm, 1319 nm, and 1415 nm. Very good agreement between the measured resonant wavelengths and the numerical results is obtained. We also fabricate the selectively gel-filled LPFGs to reduce the propagation losses by utilizing a simple selectively blocking technique. In addition, we measure and discuss the sensing sensitivities of the UV-induced LPFGs, including the temperature, strain, curvature, torsion, and surrounding refractive index (SRI) sensitivities. The measured sensitivity to temperature is 1.7 nm/¢XC from 25 ¢XC to 45 ¢XC. As the surrounding refractive index is increased to 1.377, the dip position has a maximum shift of 2 nm. Compared with other LPFGs, the UV-induced LPFGs are more insensitive to bending and strain due to the complete cladding structure. This could benefit the stability of the temperature sensors, based on our UV-induced LPFGs.

Fiber coils had been widely investigated as optical current sensors for a long time. In this thesis we have fabricated the LMA-10 PCF coils. By using the Sagnac fiber loop, we can obtain the transmission spectrum of the PCF coils. The measured birefringence of the SMF coil and the PCF coil are 1.49¡Ñ10^-5 at £f= 959.27 nm and 1.31¡Ñ10^-5 at £f = 1264.3 nm, respectively. The birefringence of the SMF coil agrees well with the theoretical result. The properties of PCF coils for variant fiber turns and cylinder sizes are discussed. As we increase the number of fiber turns, the fringe spacing becomes smaller due to the increasing phase difference. The birefringence of the PCF coil decreases with the increasing cylinder radius. Besides, we also measure the temperature sensitivities of the SMF coil and PCF coil to be 130 pm/oC and 64.55 pm/ oC, respectively. We have also demonstrated the sensing properties of the PCF coils. By introducing a displacement along the cylinder, the bending on the PCF coil can be induced. The measured bending sensitivity is -3.732 nm/m^-1. In addition, the water depth sensing properties are obtained by horizontally and vertically immersing the PCF coils into the water. As we put the PCF coil horizontally into the water, the shift of the measured spectra shows a exponential relation to the water depth. As for the vertically immersed PCF coil, the linear water depth sensitivity is -11.658 nm/cm. Finally, we propose the transverse displacement sensor based on the PCF coil. The measured sensitivity to transverse displacement can be as large as 903.9 nm/cm.

Semiconductor has electronic bandgap because of the periodic potential barriers. Similarly, as shown in Yablonovitch and John¡¦s original idea in 1987, and the optical bandgap can be formed by arranging the dielectric material periodically, named photonic crystal. The innovation promotes vigorous development in the last twenty years. Many applications were discovered by using the idea of photonic crystal, such as waveguide, left-hand material, slow light, optical register, etc. Conventional fibers guide light in the core by the total internal reflection principle, but Russel and co-workers demonstrated fibers with a so-called photonic crystal cladding in 1996, and these fibers guide light by a new physical mechanism different from traditional fibers. Photonic crystal fibers can be simply divided into two groups, one is index guiding fiber and the other is photonic bandgap fiber. Both of them have 2D periodic structures with designed defect structure in the center. Hence light can be confined and guided by special defect modes. We have successfully demonstrated microstructured fibers which have 2D periodic structure by LHPG method. During the fabrication processes, capillaries may collapse due to the surface tension. We discuss the hole-collapse issue and our solution. Besides, the quality of fiber extremely depends on the stability of laser power of the LHPG system, so we design an efficient feedback control to improve it. We also discuss the fibers¡¦ SEM images and optical properties. Finally the future work refers to the drawing of 3D photonic crystal fiber and improving the sharp thermal gradient by using a sapphire tube.

Abstract The AAO membrane with nanopore arrays were fabricated by anodizing highly pure aluminum foils (99.9995%) in electrolyte under steady voltage. Pore diameter can be controlled by different anodic voltage(from 30 to 50 V) and electrolyte, on the other hand, thickness is proportioned to anodizing time , and interpore could follow this rule(a = 15.4+2.63¡Ñv) , and minimum radius of pore could reach 15nm . The XRD spectra of AAO without and with annealing, both showed the diffraction peaks of (311)¡B(400)¡B(440), corresponding to the £^-Al2O3 phase . Before fabricating AAO, we would polish under low temperature and then clean alumina foil in order to reduce surface roughness that is good for better order and regular. Through the use of porous anodic alumina masks, Au nanodot arrays deposited on Si by E-gun with AAO mask. Subsequently, the AAO mask was removed by H3PO4. Under the same procedure, we can fabricate 80nm of the diameter of pore and apply this mask on wafer of laser constructure . Because of regular hexagonal pore array, we may get the photonic crystal effect. During PL experiment, we got the result that AAO could increase light extraction of quantum dot from C237 wafer and controlled emission peak from C238 and C196 wafer and position of peak could shift to 1140nm. We hope nanodot array on wafer of laser structure could control emission peak.

Photonic crystals (PCs) are structures with spatially periodic variations in dielectric constants. The prime property of PCs is the existence of the photonic band gaps (PBGs) which could prohibit the propagation of light within a certain frequency range. Once the PC structures are fabricated, it is hard to tune their optical properties for the fixed geometries. Thus, it is important to develop tunable PC waveguide devices for the applications in the photonic integrated circuits. We utilize the mode-gap effect to design two-dimensional (2-D) tunable Y-shaped PC waveguides with the polyaniline type electrorheological (ER) fluids. The propagation of light on the Y-shaped waveguide can be controlled by applying the electric field in specific regions. Besides, we also propose a tunable multi-channel PC waveguide with the polyaniline type ER fluids. We then investigate the tunable propagation characteristics of a 2-D single line-defect PC waveguide with liquid crystals (LCs) by varying the direction of LCs and the hole sizes. We also simulate the tunable optical properties of a 2-D Y-shaped PC waveguide utilizing LCs. Finally, we consider a 3-D Y-shaped PC slab waveguide with LCs. The effects of the direction of LCs and the slab thickness are discussed.

A novel selective-filling technology of photonic crystal fibers (PCFs) employing a simple selective-blocking process using UV gel is demonstrated in this thesis. In this study the liquid-filled PCFs with the filling in inside three layers and whole four layers represent the insertion loss of gel 7.5dB and the photonic band gap (PBG) guiding effect at wavelength 1100nm~1300nm, having potential to be tunable optical filters by filling the liquid crystal. The liquid-filled PCFs without the filling of the most inside 1ayer represent low insertion loss of gel 2dB and the total index reflection (TIR) guiding effect, having potential to be low loss tunable fiber gratings by filling the liquid crystal. The liquid-filled PCFs with the filling in middle a layer represent the elliptical far field pattern and effect of birefringence at wavelength 1600nm.

<p>This thesis presents results in two different neighboring areas of research: the magnetic properties of thin ferrite films and the application of the films in two-dimensional photonic crystals. </p><p>In the first part, we investigate the accuracy of the customary method for determining the magnetic anisotropy constants of ferrite films by ferromagnetic resonance (FMR) experiment. We have improved the method and introduced an experimental procedure to obtain the anisotropy constants with higher precision. The magnetic anisotropy fields are obtained by using FMR on a (111)-oriented yttrium iron garnet (YIG) film made by pulsed laser deposition. Moreover, we found experimentally that the shapes of FMR spectra of laser deposited epitaxial YIG films strongly depend on the orientation of the magnetic bias field with respect to the crystalline axes of the film. Inhomogeneities of the constants of anisotropy throughout the film could be responsible for the complexity of the FMR spectra. We find the special directions of the applied magnetic field in which the contribution of the magnetocrystalline anisotropy has the smallest effect on the ferromagnetic resonance and therefore on the elements of the permeability tensor. </p><p>In the second part, we study the electromagnetic wave propagation in two-dimensional (2D) dielectric and magneto-optic photonic crystals (PCs). We have proposed a 2D PC which is composed of magneto-optic material for the purpose of the enhancement of Faraday rotation in high transmission. It is assumed that the 2D PC contains a bismuth iron garnet (BIG) film either as the PC background medium or as a defect, embedded in the 2D PC. We have examined theoretically and computationally the increase in the Faraday rotation as well as the transmission of a plane-polarized plane wave incident onto these structures in the optical wavelength regime. Several important phenomena, with potential applications, are observed.</p>