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30 Sep 2004
The pick of this week's applications including a VCSEL that emits multiple wavelengths simultaneously.
• Title: Multi-color semiconductor lasers
Applicant: Orlee Light Innovations, Israel
International application number: WO 2004/082084
An Israeli company is trying to patent a vertical-cavity surface-emitting laser (VCSEL) that emits multiple wavelengths simultaneously. The device contains several active layers adapted to amplify different wavelengths and two distributed Bragg reflectors. The VCSEL can be configured to emit light through the substrate or a transparent electrode. "An array of multi-wavelength VCSEL structures of this sort may be formed together on a common substrate in order to create an intense, high-efficiency light source," say the authors.
• Title: Security label which is optically read be terahertz radiation
Applicant: The University Court of the University of Glasgow, UK
International application number: WO 2004/081545
A security label that is read by terahertz radiation is unveiled in patent application WO 2004/081545. The authors believe this is an alternative to expensive radio frequency ID cards which use an inductive loop and a microchip containing the private information. The security tag comes in the form of a hologram that can only be viewed by using radiation of ideally around 500GHz. It can be designed to operate in either transmission or reflective mode. "The terahertz tag may be covered by a material opaque to visible light, but transparent or transmissive of terahertz wavelengths, making it difficult for potential fraudsters to investigate the terahertz image," say the inventors.
• Title: Coiled optical fiber assembly for measuring pressure and/or other physical data
Applicant: Shell Internationale Research Maatschappij, the Netherlands
International application number: WO 2004/081509
Quantities such as pressure, temperature, elongation and torsion can be measured using conventional optical fibers embedded into a tube, according to patent application WO 2004/081509. Crucially, the inventors from Shell say their idea does not rely on fiber Bragg gratings. Deformation of the tube induces strain in each optical fiber. Laser pulses are fired into the fibers and a detector monitors any shift in wavelength of the pulses scattered from various locations along the fiber. A signal processor then calculates a strain pattern along the length of the fiber. "Preferably several fibers are wound at different pitch angles and in different directions and diameters in the wall of the tube," say the authors. "The tube may be arranged along at least part of the length of an inflow region of an oil or gas production well."
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