Optical grating fabrication process

US6753118B2 · kind B2 · utility

Assignee

• Fitel USA Corp. · US

Inventors

• Rajan D. Deshmukh · Yardley, US
• Benjamin John Eggleton · Summit, US
• Pavel Ivanoff Reyes · New Providence, US
• Carl Edmund Soccolich · Flemington, US
• Michael Sumetsky · Birmingham, GB
• Paul S. Westbrook · Bound Brook, US

Key dates

• Filing date: Mar 27, 2002
• Grant date: Jun 22, 2004
• Expiry date: Dec 4, 2022

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B6/02138
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A grating fabrication process utilizes real-time measurement of a grating characteristic (such as, for example, grating period chirp, reflectivity, group delay) as a feedback error signal to modify the writing process and improve the characteristics of the finished grating. A test beam is launched through the optical medium during the writing process (or at the end of an initial writing process) and a particular characteristic is measured and used to generate a “corrective” apodization refractive index profile that can be incorporated with the grating to improve its characteristics. The improvements may be applied to a phase (or amplitude) mask used to write the grating (etching, local deformation, coating changes, for example), or the grating itself may be corrected using additional UV exposure, non-uniform annealing, non-uniform heating, and/or non-uniform tension—these techniques applied separately or in an intermittent sequence. The utilization of a “closed loop” grating fabrication process provides the ability to form gratings with finely tuned characteristics.