Zeitschrift für Laser, Optik und Photonik

Bloch theorem for a periodic operator is being revisited here, and we notice extra orthogonality relationships. It is shown that solutions are bi-periodic, in the sense that eigenfunctions are periodic with respect to one argument, and pseudo-periodic with respect to the other. An additional kind of symmetry between r-space and k-space exists between the envelope and eignfunctions not apparently noticed before, which allows to define new invertible modified Wannier functions. As opposed to the Wannier functions in r-space, these modified Wannier functions are defined in the k-spaces, but satisfy similar basic properties. These could result in new algorithms and other novel applications in the computational tools of periodic structures.

Investigation of glucose in intralipid using microstructure optical fiber is reported in this paper. The optical fiber is realized by 5 × 5 air holes on square lattice silicon substrate. The principle of measurement of glucose in intralipid is based on the variation of electric field with respect to percentage of glucose. The simulation for electric field distribution is done using plane wave expansion method, where optimization is realized by varying radius of air holes and lattice spacing of crystal structure. With varying both radius and lattice spacing and employing PWE method, simulation result revealed that both peak electric field and output power emerging from microstructure fiber increases with the increase of glucose concentration for certain radii and lattice spacing. Aside this present result divulged that microstructure fiber with lattice spacing of 1 μm and radius of air holes of 300 nm is suitable to investigate glucose in an intralipid. Finally an experimental setup is proposed to measure the glucose concentration.

Disperse red 13 (DR13) azoaromatic chromophores were incorporated into sol-gel derived TiO2/organically modified silane matrix to achieve a hybrid material doped with dye molecules. Nonlinear optical properties of the asprepared hybrid material were investigated by an optical Kerr shutter technique with an 800-nm femtosecond laser. It is obtained that the response time of the bulk sample doped with 0.1% DR13 molecules is less than 208 fs and the third-order nonlinear refractive index is estimated at about 1.141×10-15 cm2/W. It is also found that the sample of material with higher DR13 content could be with higher third-order nonlinear susceptibility. The linear refractive index and the thickness of the hybrid films derived by a spin-coating process were also studied by a prism coupling technique. It is found that with an increasing of the baking temperature, both the refractive index and the thickness of the hybrid films decrease. Absorption spectra, microstructural and morphological properties of the hybrid films were also characterized by UV–Vis absorption spectroscopy, thermal gravimetric analysis, Fourier-transform infrared spectroscopy and atomic force microscopy. Results indicate that the as-prepared hybrid material is expected to be potential in ultrafast photonic applications.

A rectangular PCF structure in BK7 glass with inner and outer cladding is used to investigate effective mode field area, high nonlinear coefficient, and confinement loss and dispersion property using 2D FDTD technique. The PCF structure is purposed to design with pitches and air hole diameter in a periodic array fashion. The different properties of PCF structure like mode field area, nonlinear coefficient, confinement loss and dispersion are to be analyzed. The variation is investigated with change of different parameters like Ʌ1 1 1 d Λ , 2 1 Λ Λ , and d1/d2 for a wide range of wavelength. The proposed rectangular PCF structure has slightly more nonlinear coefficient (γ=36.98 W-1km-1) than the highly nonlinear silica photonic crystal fiber (γ=35 W-1 km-1) at a wavelength of 1.55 μm with almost same mode field area (Aeff ~ 2.8 μm2). This result seems to be important in super-continuum generation and nonlinear fiber optics.