Integrated all-optical infrared switchable plasmonic quantum cascade laser

We report a type of infrared switchable plasmonic quantum cascade laser, in which far field light in the midwave infrared (MWIR, 6.1 μm) is modulated by a near field interaction of light in the telecommunications wavelength (1.55 μm). To achieve this all-optical switch, we used cross-polarized bowtie antennas and a centrally located germanium nanoslab. The bowtie antenna squeezes the short wavelength light into the gap region, where the germanium is placed. The perturbation of refractive index of the germanium due to the free carrier absorption produced by short wavelength light changes the optical response of the antenna and the entire laser intensity at 6.1 μm significantly. This device shows a viable method to modulate the far field of a laser through a near field interaction.     

Analysis of rate-dependent tensile properties of polypropylene fibres used in thermally bonded nonwovens

The stress–strain behaviour of polypropylene fibres is evaluated for various tensile strain rates. Fibre samples are extracted from a thermally bonded nonwoven and fixed in a low-load tensile test machine. A methodology is introduced to implement a constant true strain rate at high strain tests for conventional tensile test machines. The obtained results indicate that polypropylene fibres show a highly viscous behaviour, especially during the initial stage of load application. No significant difference in a tensile behaviour of fibres was observed for loading regimes with a constant true strain rate and a constant engineering strain rate.     

Magnetic resonance imaging of intramuscular haemangiomas with emphasis on contrast enhancement patterns

A total of 21 patients with psychogenic tremor (PT) were asked to take part in a neurologic and psychosomatic assessment; for 17 patients follow-up information was also recorded. Women out-numbered men in the sample. In the majority of patients the tremor was associated with a variety of other conversion symptoms. The clinical picture of the tremor varied. After beginning exclusively in the extremities, it tended to spread to other parts of the body. Other psychopathology (depression and histrionic personality disorder) existed in almost a third of the sample. Many patients had retired from professional life, or planned to do so in the near future, because of PT. At follow up the initial diagnosis was confirmed in all patients although in some patients additional physical illness had developed during the follow-up period. When neurological and psychiatric/psychosomatic criteria are applied the diagnosis of PT can be established reliably. Studies that have questioned the validity of the conversion concept on the basis of frequent misdiagnoses may indicate problems in the diagnostic procedure rather than an invalid theoretical construct.     

Modelling the pattern creation process for the optimum design of a circular warp-knitting machine using a conical needle-bed

A circular warp-knitting machine was designed using a novel approach that uses a conical needle-bed. This machine was built and successfully tested. The interaction between the patterning and knitting mechanisms of a warp-knitting machine is critical for the performance of the machine. In a circular warp-knitting machine, geometric parameters such as the diameter of the patterning rings and the distance between the patterning rings and the needles can significantly affect the patterning capability of the machine. This paper describes an approach to modelling the yarn and needle paths in a novel circular warp knitting machine with a conical needle-bed and patterning rings, using equations that govern the relationship between the different geometric parameters in order to calculate the amplitude of the shogging movements and optimise machine performance. A set of mathematical equations governing the geometric relationship that determines the limits of the motion of the patterning rings is presented. The algorithms have been created and successfully tested using a case study. A mathematical model and appropriate algorithms are developed that prove useful design tools for the designer of the circular warp knitting machines using conical needle-bed.     

A Novel Self-aligned and Maskless Process for Formation of Highly Uniform Arrays of Nanoholes and Nanopillars

Fabrication of a large area of periodic structures with deep sub-wavelength features is required in many applications such as solar cells, photonic crystals, and artificial kidneys. We present a low-cost and high-throughput process for realization of 2D arrays of deep sub-wavelength features using a self-assembled monolayer of hexagonally close packed (HCP) silica and polystyrene microspheres. This method utilizes the microspheres as super-lenses to fabricate nanohole and pillar arrays over large areas on conventional positive and negative photoresist, and with a high aspect ratio. The period and diameter of the holes and pillars formed with this technique can be controlled precisely and independently. We demonstrate that the method can produce HCP arrays of hole of sub-250 nm size using a conventional photolithography system with a broadband UV source centered at 400 nm. We also present our 3D FDTD modeling, which shows a good agreement with the experimental results.     

On the Source of Jitter in a Room-Temperature Nanoinjection Photon Detector at 1.55 $mu hbox{m}$

The transient response of a nanoinjection infrared photon detector was studied by exploring the relation between lateral charge transfer and jitter. The jitter of the device was measured to be 15 ps at room temperature. The jitter was almost independent of the pulse power, even after device saturation. Spatial maps for delay and amplitude were acquired. The carrier velocity was extracted from the measurements and compared with that of the simulation model. The jitter due to transit time was calculated to be in agreement with the measured data, which indicated that the jitter is primarily transit time limited.     

Fabrication of Large Area Periodic Nanostructures Using Nanosphere Photolithography

Large area periodic nanostructures exhibit unique optical and electronic properties and have found many applications, such as photonic band-gap materials, high dense data storage, and photonic devices. We have developed a maskless photolithography method—Nanosphere Photolithography (NSP)—to produce a large area of uniform nanopatterns in the photoresist utilizing the silica micro-spheres to focus UV light. Here, we will extend the idea to fabricate metallic nanostructures using the NSP method. We produced large areas of periodic uniform nanohole array perforated in different metallic films, such as gold and aluminum. The diameters of these nanoholes are much smaller than the wavelength of UV light used and they are very uniformly distributed. The method introduced here inherently has both the advantages of photolithography and self-assembled methods. Besides, it also generates very uniform repetitive nanopatterns because the focused beam waist is almost unchanged with different sphere sizes.     

Parametric code for generation of finite‐element model of nonwovens accounting for orientation distribution of fibres

A novel finite‐element modelling code developed to investigate the structural behaviour of nonwoven materials is presented. The technique allows modelling of a nonwoven fabric as a continuous–discontinuous medium with a given pattern of bond points and a large number of constituent fibres with arbitrary orientation distribution. The parametric feature of the code provides automatic modelling of nonwoven materials according to design parameters in a very efficient way. The effect of fibre length is also included for the first time in a finite element model of a nonwoven. The developed code is very flexible and it is possible to be extended to further studies such as damage behaviour.Copyright © 2013 John Wiley & Sons, Ltd.