Papers by Keyword: Birefringence

Abstract: This paper mainlyintroduces the basic optical principles of light. Using He-Ne laser and pinhole configure collimated illumination, measuring the index of refraction by minimum deviation method, and measuring the birefringence use of wedge method by transmission optical microscope. In addition, give the results and discussion of the whole experiments.

Abstract: Highly birefringent extruded elliptical-hole photonic crystal fibers (PCFs) with single defect and double defect are proposed and investigated, which are supposed to be achieved by extruding conventional triangular-lattice circular-hole PCFs. Comparative research on the birefringence and the confinement loss of the proposed PCFs with single defect and double defect is presented. Simulated results show that the proposed extruded elliptical-hole PCFs with single defect and double defect can be with high birefringence up to the order of 10-2. Confinement loss increases when the ellipticity of the air hole of the proposed PCFs increases, which nevertheless can be overcome by increasing the ring number or the area of the air holes in the fiber cladding.

Abstract: Using 6H SiC wafers including regions with a varying residual stress, the birefringence pattern of almost vertical dislocations is measured and modeled. We show that it is possible to identify the basal plane component of "small" dislocations by a quantitative fit of the birefringence pattern. Combining birefringence and etch pit detection after KOH etching shows that most of the vertical dislocations are of a mixed nature, exhibiting both an edge and a screw component.

Abstract: In this work, different types of nanostructured systems containing azobenzene groups were studied. With that aim, firstly, novel azo-functionalised block copolymers (BCP) were synthesized from epoxidized poly (styrene-b-butadiene-b-styrene) (SBS) modified with azobenzene units by one-step facile reaction between the epoxy groups and an azo-amine. The epoxy/amine reaction was verified by Fourier transform infrared spectroscopy. In addition, the effect of covalent attachment of the azobenzene moieties was investigated by analyzing the morphology and the optical anisotropic response of the resulting azo-containing BCP, with respect to solution mixing of the azobenzene as a guest in the BCP host without chemical bonding. On the other hand, epoxidized SBS was also used as template for the generation of nanostructured thermosetting epoxy matrices with azobenzene groups covalently linked. This BCP can self-assemble in the epoxy matrix to produce microphase-separated domains, thanks to the selective segregation of polystyrene blocks due to reaction induced microphase separation. In this case, the influence of the azobenzene content and the amount of epoxidized SBS on the generated morphologies and the photo-induced anisotropy was studied.

Abstract: Resonance integrated optical gyroscope, Polarization-maintaining waveguide, Single-mode condition, Birefringence. Abstract. A polarization-maintaining (PM) waveguide used in Resonance Integrated Optical Gyro (RIOG) is theoretically proposed. Three essential factors determining the PM performance, which are the single-mode condition, birefringence and core index, are analyzed and optimized respectively. The single-mode rectangular waveguide is obtained by analyzing the propagation mode of the rectangular waveguide. A high birefringence waveguide design method is brought up according to the theory of geometrical birefringence, realized by changing the cross-sectional shape of the waveguide. The effect that the core index contributes to the birefringence is also discussed, and an optimal core index of the waveguide to reach maximal birefringence is determined in the condition of single-mode transmission. The high birefringence PM Waveguide with geometrical birefringence of 1.5×10-4 is obtained by theoretical analysis, the simulation results shows that the polarization cross-talk in RIOG is obviously improved.

Abstract: A new type of photonic crystal fiber (PCF) with pentagonal air-core is proposed, which consists of octagonal air holes in the cladding. In addition, five elliptical air holes are embedded in the inner layer to enhance the birefringence characteristic. Characteristics of this PCF are analyzed by using of Finite Element Method (FEM). Numerical results show that this kind of PCF exhibits high birefringence with the level of 0.001 after optimization, which will find application in optical sensing systems.

Abstract: Aiming at the requirements of high performance of optical communication systems, a new type of photonic crystal fiber (PCF) is proposed. This kind of PCF consists of hexagonal air holes in the inner cladding and octagonal air holes in the others layers. Two big elliptical air holes are embedded to enhance the birefringence. Numeral results show that this kind of PCF exhibits high birefringence with the level of 10-3 and high nonlinearity with the level of 10-2m-1w-1. In addition, two zero dispersion points are obtained after optimization, which will find application in dispersion compensation PCFs.

Abstract: In this paper we report a method for reduce the birefingence of polymer optical fiber by using high pressure carbon dioxide fluids. Polymer optical fiber, in the manufacturing and forming process, it is effected by the external drawing and cooling so that the optical fiber presents exhibit birefringence. The experimental result shows that after the treatments of carbon dioxide fluids, the birefringence of optical fiber drop from 2-2.1×10^{- 4} to 4.1-4.6×10^{- 5} .

Abstract: The transmission properties of polycrystalline transparent ceramics are influenced by the chemical composition and the microstructure of the material. The fundamental optical mechanism of transparent ceramics and the influencing factors on transmission properties were discussed in this paper. The Mie theory for light scattering is applied to calculate scattering coefficients of residual pores and optical birefringence. The in-line transmission curves of the transparent alumina were calculated as a function of pore size, porosity and grain size. The results show that scattering by the residual pores is the dominant influencing factors on transmission properties. The scattering by the residual pores increases with an increase in porosity and the maximum of the scattering was observed when the pore size close to the optical wavelength. Optical birefringence in the transparent ceramics with non-cubic crystal structure has an important effect on the in-line transmission. The in-line transmission increases with a decrease in grain size. Keywords: transparent ceramics; microstructure; light scattering; birefringence

Abstract: The nature of the phase transitions across isotropic–nematic (IN) and nematic–smectic-A (N-SmA) are carried out using density measurements in N-(p-n-ethoxy benzylidene)-p-n-pentyl aniline, 2O.5, N-(p-n-methoxy benzylidene)-p-n-pentyloxy aniline, 1O.O5, N-(p-n-ethyl benzylidene)-p-n-dodecyl aniline, 2.12 and N-(p-n-butyl benzylidene)-p-n-dodecyl aniline, 4.12. The compounds exhibit IN, IN, IN and INSmA phase sequences respectively with varying thermal ranges suitable for the study of birefringence. The birefringence studies are carried out using Newton’s rings and wedge techniques which provide δn = (n_e - n_o) (the birefringence) n_e, and n_o respectively. The orientational order parameter, S is evaluated (i) directly from δn and Δn (the birefringence in perfect order), independent of the local field that the nematic molecule experiences and (ii) from molecular polarizabilities estimated from n_e, n_o and density values assuming isotropic as well as anisotropic field that the nematic molecule experiences. The estimated order parameter from the different techniques is compared with one another and with the literature data.