25 Feb 2004
The pick of this week’s patent applications including a way to make scatter-free optics that operate at less than 200 nm.
• Title: Scatter-free UV optical fluoride crystal elements for <200 nm laser lithography and methods
Applicant: Corning Incorporated, US
International application number: WO 2004/015461
Corning is trying to patent a method which it claims produces scatter-free fluoride-based lithography crystals for use with sub-200 nm light. According to the authors, the technique involves melting a calcium fluoride feedstock in a graphite crucible which contains < 0.3 ppm of chlorine. The authors then grow a calcium-fluoride scatter-free crystal from the melt. The resulting crystal is said to have a chlorine concentration of less than 0.25 Cl by weight.
• Title: Optical fiber for Raman amplification
Applicant: Pirelli & C.S.P.A, Italy
International application number: WO 2004/015828
Pirelli is trying to patent its recipe for making optical fibers for use in Raman amplifiers. Based on a tellurite-glass, one or more specific metal oxides are added to the fiber. The end result is said to be a fiber with improved Raman gain and thermal properties, such as the fiber’s thermal stability index. According to the authors, the maximum Raman gain of their fiber is typically 100 times higher than its pure silica counterpart.
• Title: Tunable ring laser with external grating operating in a single mode
Applicant: The University of Bristol, UK
International application number: WO 2004/015827
Scientists at the University of Bristol in the UK have applied to patent their tunable ring-cavity laser. The device contains a gain element, bi-directional output coupler and a frequency selector, typically a grating. “Single mode laser operation is achieved where a cavity mode frequency of the cavity coincides with a grating reflection frequency,” say the inventors. They add that the refractive index of the grating can be modified using a variable injection current. By varying the current, the output wavelength can be quickly tuned to any cavity mode frequency.