Assembly of laser-fiber arrays

This paper describes techniques and machinery for first-level packaging of laser-to-fiber interconnects using batch assembly and active alignment. These techniques are economical because the costs of labor-intensive processes, such as parts handling, fiber-polishing, and alignment, are shared among the many elements of the array. Using these techniques, prototype packages have been built consisting of 32-wide arrays of 1300 nm lasers coupled to 32-wide arrays of single-mode fiber-optic stubs. Building the package involves three steps: (1) preparing the laser array for handling and alignment by soldering it to a metallized silicon carrier; (2) building the fiber array by stripping the fibers, placing them precisely into etched silicon V-grooves, bonding them in place, and polishing both ends; and (3) aligning the two arrays to each other using batch, active alignment. Batch alignment succeeds to the extent that each array is collinear, so the collinearity achieved in processes (1) and (2) is crucial. Typically, collinearity of ±1 μm or better is achieved for each array. When such arrays are batch aligned using the techniques described herein, the average coupling efficiency is about 88% as large as it would be if each laser-fiber pair were optimally aligned individually     

Order and characteristic of parabolically differentiable points

Summary Conditions are given for the union of two arcs of parabolic order four in the affine plane to be an arc of parabolic order four, and for an arc of parabolic order four to be extensible to a larger arc of parabolic order four. A characteristic of a parabolically differentiable interior point p of an arc is defined, and it is shown that the parabolic order of p is at least as great as the sum of the digits of the characteristic of p. If, in addition, p is the common end-point of two arcs of minimal parabolic order, then the parabolic order of p is equal to the sum of the digits of its characteristic. In memory of Guido Castelnuovo in the recurrence of the first centenary of his birth. The second author gratefully acknowledges the support of the National Research Council of Canada. Part of this research was done while the first author was a Fellow of the Summer Research Institute of the Canadian Mathematical Congress.     

Conversion effect on the reaction CF3 + HCN. Analysis of I2 and I participation with CF3I as radical source

The gas-phase reaction of CF₃ with HCN has been examined over a wide conversion range using CF₃I as a thermal and photolytic source of radicals. Quantitative and qualitative results show a significant increase of the specific rate constant for the hydrogen abstraction reaction relative to CF₃ recombination when reaction is carried out under ultraviolet irradiation. This “extra” formation of the reaction product, CF₃H, has been assigned to the participation of iodine in this system through the formation of a (I-HCN) intermediate. Arrhenius parameters obtained for the addition mechanism of I to HCN do not seem to conform to a single reaction step, on the contrary, they correspond to a more complex reaction scheme.     

Cyclo-hydrosilylation: A novel route to siloxetanes and silanones

A novel and convenient method for the apparent liquid phase generation of dimethylsilanone, Me₂SiO (D₁), based on readily obtainable reactants and employing conventional temperatures (50–150°) is reported herein. Platinum catalyzed hydrosilylation of vinyldimethylcaarbinoxydimethylsilane (I) appears to proceed by an exclusively intramolecular path to produce not only the expected 5-membered heterocyclic, 1,1,3,3-tetramethyl-2-oxa-1 silacyclopentane (V), but also the isomeric and highly unstable 4-membered siloxetane, 1,1,3,3,4-pentamethyl-2-oxa-1-silacyclobutane (IV). The intermediacy of IV is suggested by the products: i.e., 2-methyl-2-butene which is believed to arise along with Me₂SiO from fragmentation of IV; D₃ and D₄ from D₁ self-coupling; a 6-membered cyclic derived from insertion of D₁ into the Si-O bond of IV, i.e., 1,1,3,3,5,5,6-heptamethyl-2,4-dioxa-1,3-disilacyclohexane (VI); a polymer which upon alkaline cracking produces more 6-ring (VI) but little or no 5-ring (V) suggesting that the polymer arose from copolymerization of D₁, D₂, and siloxetane (IV). Compound I is also an excellent thermolytic source of D₁ as evidenced by the formation of the expected derivatives upon heating in the presence of known silanone traps.     

Fiber-optic confocal microscopy using a spatial light modulator

We present a novel fiber-optic confocal microscope in which the scanning operation is achieved by use of a spatial light modulator (SLM) to sequentially illuminate individual fibers or patterns of multiple fibers. Experimental images are presented, and the optical-sectioning capability of the device is demonstrated. The novel SLM-based system is more optically efficient, achieves higher contrast, and has improved optical-sectioning capabilities compared with those of other proposed instruments for confocal microendoscopy.     

CPT and lorentz tests with muons

Precision experiments with muons are sensitive to Planck-scale CPT and Lorentz violation that is undetectable in other tests. Existing data on the muonium ground-state hyperfine structure and on the muon anomalous magnetic moment could be analyzed to provide dimensionless figures of merit for CPT and Lorentz violation at the levels of 4x10(-21) and 10(-23).