The Photonic Lantern

Photonic lanterns are made by adiabatically merging several single-mode cores into one multimode core. They provide low-loss interfaces between single-mode and multimode systems where the precise optical mapping between cores and individual modes is unimportant.Comment: 45 pages; article unchanged, accepted for publication in Advances in Optics and Photonic

Development of Advanced NDE Ultrasonic Equipment

Recent studies to determine the probability of detection of nondestructive examination methods by the Air Force indicate that these capabilities are severely limited. One of the factors contributing to the insufficiency of ultrasonic testing is related to a general lack of versatility and capability of commercial ultrasonic equipment. Inadequate instrument reliability, inconsistent components including transducers, and uncertain calibration standards further compromise the potential utility of this method. Battelle Pacific Northwest Laboratories, under the sponsorship of the manufacturing Technology Division of the Air Force Materials Laboratory, is developing an advanced ultrasonic nondestructive testing system directed at resolving these defficiencies. As a result, this program will establish a modular ultrasonic system specification that will prevent near term obsolescence by permitting the addition of new technology such as ARPA developments in the form of additional or replacement modules. This paper will describe the Phase I and II tasks and objectives which are planned to establish an equipment specification, demonstrate initial prototype systems, and provide a procurement specification and technical manuals. Progress to date will be summarized

The high-lying 6^6Li levels at excitation energy around 21 MeV

The $^3$H+$^3$He cluster structure in $^6$Li was investigated by the $^3$H($\alpha$,$^3$H $^3$He)n kinematically complete experiment at the incident energy $E_\alpha$ = 67.2 MeV. We have observed two resonances at $E_x^*$ = 21.30 and 21.90 MeV which are consistent with the $^3$He($^3$H, $\gamma$)$^6$Li analysis in the Ajzenberg-Selove compilation. Our data are compared with the previous experimental data and the RGM and CSRGM calculations.Comment: 12 pages, 6 figures. Accepted for publication in J. Phys. Soc. Jp

Resonant Bend Loss in Leakage Channel Fibers

Leakage channel fibers, designed to suppress higher-order modes, demonstrate resonant power loss at certain critical radii of curvature. Outside the resonance, the power recovers to the levels offset by the usual mechanism of bend-induced loss. Using C$^2$-imaging, we experimentally characterize this anomaly and identify the corresponding physical mechanism as the radiative decay of the fundamental mode mediated by the resonant coupling to a cladding mode.Comment: 3 pages, 4 figures, submitted to Optics Letter

Magic wavelengths for the np-ns transitions in alkali-metal atoms

Extensive calculations of the electric-dipole matrix elements in alkali-metal atoms are conducted using the relativistic all-order method. This approach is a linearized version of the coupled-cluster method, which sums infinite sets of many-body perturbation theory terms. All allowed transitions between the lowest ns, np_1/2, np_3/2 states and a large number of excited states are considered in these calculations and their accuracy is evaluated. The resulting electric-dipole matrix elements are used for the high-precision calculation of frequency-dependent polarizabilities of the excited states of alkali-metal atoms. We find magic wavelengths in alkali-metal atoms for which the ns and np_1/2 and np_3/2 atomic levels have the same ac Stark shifts, which facilitates state-insensitive optical cooling and trapping.Comment: 12 pages, 8 figure

Low-loss criterion and effective area considerations for photonic crystal fibers

We study the class of endlessly single-mode all-silica photonic crystal fibers with a triangular air-hole cladding. We consider the sensibility to longitudinal nonuniformities and the consequences and limitations for realizing low-loss large-mode area photonic crystal fibers. We also discuss the dominating scattering mechanism and experimentally we confirm that both macro and micro-bending can be the limiting factor.Comment: Accepted for Journal of Optics A - Pure and Applied Optic

Diffusion with rearranging traps

A model for diffusion on a cubic lattice with a random distribution of traps is developed. The traps are redistributed at certain time intervals. Such models are useful for describing systems showing dynamic disorder, such as ion-conducting polymers. In the present model the traps are infinite, unlike an earlier version with finite traps, this model has a percolation threshold. For the infinite trap version a simple analytical calculation is possible and the results agree qualitatively with simulation.Comment: Latex, five figure

Propagation of Light in Photonic Crystal Fibre Devices

We describe a semi-analytical approach for three-dimensional analysis of photonic crystal fibre devices. The approach relies on modal transmission-line theory. We offer two examples illustrating the utilization of this approach in photonic crystal fibres: the verification of the coupling action in a photonic crystal fibre coupler and the modal reflectivity in a photonic crystal fibre distributed Bragg reflector.Comment: 15 pages including 7 figures. Accepted for J. Opt. A: Pure Appl. Op