A parallelized multi-degrees-of-freedom cell mapping method

Cell mapping methods, in general, provide a computationally efficient way to analyze the long-term global dynamics of lower-dimensional systems. The multi-degrees-of-freedom cell mapping (MDCM) method, in particular, overcomes the scaling limitations of other cell mapping methods, allowing efficiency benefits to be realized for higher-dimensional systems. Unfortunately, the sequential structure of the MDCM algorithm limits the ability to utilize the parallel processing capabilities of modern computers. In this paper, the parallelized multi-degrees-of-freedom cell mapping (PMDCM) method is introduced. The PMDCM method features a restructured algorithm that employs parallel computation to streamline one of the most time-consuming elements: numerical integration. The PMDCM algorithm is described in detail and is demonstrated by comparing results produced by the PMDCM method to those produced by MDCM and the grid-of-starts. By using the PMDCM method on a quad-core processor with 100 simultaneous integrations per mapping step, the total computation time is reduced by 93 %, as compared with the MDCM method. With PMDCM, the global integrity measure also agrees more closely with the computationally intensive grid-of-starts method when compared with the MDCM method.     

Amplification of near-infrared light in a photorefractive ring resonator

We have demonstrated efficient amplification of near-infrared, 0.83-μm and 1.06-μm light, in a photorefractive ring resonator using Rh:BaTiO₃. The optical power oscillating inside the ring exceeded the pump power by a factor of up to 2.34. The sensitivity of a ring resonator to nanometer changes in its length was characterised using a piezo-mirror. Received: 30 November 2000 / Revised version: 24 January 2001 / Published online: 20 April 2001     

On left conjugacy closed loops in which the left multiplication group is normal

A loopQ is said to be left conjugacy closed (LCC) if the left translations form a set of permutations that is closed under conjugation. This papers investigates those LCC loops where the group generated by left translations is normal in the group generated by both left and right translations.     

Laser-induced-forward-transfer: a rapid prototyping tool for fabrication of photonic devices

We propose a rapid prototyping method for the fabrication of optical waveguides based on the direct laser-printing method of ultrafast Laser-Induced Forward Transfer (LIFT) followed by further processing. The method was implemented for the fabrication of titanium in-diffused lithium niobate channel waveguides and X-couplers by LIFT-depositing titanium metal followed by diffusion. Propagation loss as low as 0.8 dB/cm was measured in preliminary experiments.     

Room-temperature continuous-wave operation of Ti:sapphire buried channel-waveguide lasers fabricated via proton implantation

Fabrication and laser operation of proton-implanted Ti:sapphire buried channel waveguides is reported for the first time to our knowledge. Without any postimplantation annealing of the structures, continuous laser operation near 780 nm was demonstrated at room temperature at an absorbed pump power threshold of 230 mW. Single-transverse-mode laser emission was observed with measured beam propagation factors M(2)(x) and M(2)(y) of 1.5 and 1.2, respectively. An output power of 12.4 mW for 1 W pump power was obtained with an output coupler of 4.6% transmission at the signal wavelength. Higher output powers were measured in waveguides with larger cross sections exhibiting multimode laser emission.     

Etching and forward transfer of fused silica in solid-phase by femtosecond laser-induced solid etching (LISE)

We present a femtosecond laser-based technique for etching and forward transfer of bulk transparent materials in solid-phase. Femtosecond laser pulses with were focused through a fused silica block onto an absorbing thin film of Cr. A constraining Si wafer was pressed into tight contact with the Cr film to prevent lift-off of the film. A combination of the high temperature and pressure of the Cr, and compressive stress from the Si, resulted in etching of smooth features from the fused silica by cracking. Unlike in conventional ablative or chemical etching, the silica was removed from the bulk as single solid-phase pieces which could be collected on the Si. Using this so-called laser-induced solid etching (LISE) technique, 1-2 m deep pits and channels have been produced in the silica surface, and corresponding dots and lines deposited on the Si. The threshold fluence for etching was found to be with duration pulses. The morphology of the etched features are investigated as functions of fluence and exposure to multiple pulses.     

The effect of relative plasma plume delay on the properties of complex oxide films grown by multi-laser, multi-target combinatorial pulsed laser deposition

We report the effects of relative time delay of plasma plumes on thin garnet crystal films fabricated by dual-beam, combinatorial pulsed laser deposition. Relative plume delay was found to affect both the lattice constant and elemental composition of mixed Gd₃Ga₅O₁₂ (GGG) and Gd₃Sc₂Ga₃O₁₂ (GSGG) films. Further analysis of the plasmas was undertaken using a Langmuir probe, which revealed that for relative plume delays shorter than 200 μs, the second plume travels through a partial vacuum created by the first plume, leading to higher energy ion bombardment of the growing film. The resulting in-plane stresses are consistent with the transition to a higher value of lattice constant normal to the film plane that was observed around this delay value. At delays shorter than 10 μs, plume propagation was found to overlap, leading to scattering of lighter ions from the plume and a change in stoichiometry of the resultant films.     

Inclusive yields and transverse spectra of non-strange mesons: Comparisons with the quark model,and an estimate of the fraction of “direct” pion production

Recent data on the production ofη, ?⁰, ω and other mesons in hadron-hadron collisions at intermediate energies are studied. Their transverse spectra dσ/dp_T² are all found to be approximately exponential, with similar slopes, ～3.4 (GeV/c)^?2, up to about p_T² = 2(GeV/c)². The inclusive yields of the mesons are broadly in agreement with quark model predictions. In the case of pions, a distimction is made between those directly produced and those produced indirectly via resonance decay. It is estimated that between 10% and 30% of pions are directly produced.     

Study of the reactions K−p → K+K−Λ and K−p → ppΛ, at 10 and 16 GeV/c

The reactions (1) K^?p → K⁺K^?Λ and (2) $\text{K}{}^{\mathrm{?}}\text{p}\text{→}\text{p}\text{p}\text{Λ}$ have been studied on samples of 109 and 64 events, respectively, at 10 GeV/c and 125 and 69 events at 16 GeV/c, reasonably free from contaminations. The investigation of the first reaction uses also 84 events of the $\text{K}{}^0\text{K}{}^0\text{Λ}$ final state at 10 GeV/c. Analysis of the Van Hove plots indicates that the K⁺K^?Λ and $\text{p}\text{p}\text{Λ}$ final states are produced by two main mechanisms: (i) a ΔQ = 0 process, with a strong diffractive component near threshold, involving the dissociations p → K⁺Λ in reaction (1) and $\text{K}{}^{\mathrm{?}}\text{→}\text{p}\text{Λ}$ in reaction (2) and (ii) a ΔQ = 1 process involving hypercharge exchange, and producing K⁺K^? and $\text{p}\text{p}$ systems in reactions (1) and (2), respectively, recoiling off the Λ. With increasing energy, this hypercharge exchange process decreases slowly when K⁺K^? is produced, but fast where the production of $\text{p}\text{p}$, violating the Zweig rule, occurs.