Invention:
Researchers at the University of Arizona College of Optical Sciences and Canada's Carleton University recently succeeded in fabricating high reflectivity (>99%) Fiber Bragg Gratings (FBGs) into phosphate glass fibers using UV light and a phase mask technique. With this new manufacturing technique, fiber lasers can be created as single monolithic units that are more stable, with higher efficiencies and shorter manufacturing times than lasers created by conventional manufacturing techniques. These FBGs show high thermal stability making them suitable for fiber lasers operating at high average power laser operation. Not only are the FBGs stable when exposed to temperatures up to 170C for extended periods (hundreds of hours), but the reflectivity actually increases under such conditions.
Both distributed Bragg reflector (DBR) lasers and distributed feedback (DFB) lasers can be made with the monolithic phosphate glass fiber. Utilizing highly doped phosphate glass in combination with a DFB geometry enables the fabrication of stable single frequency fiber lasers with Watt-level output power, a great improvement over the mW-level output power in DFB fiber lasers made of silicate glass.
Background:
The holographic technique for writing gratings in silica-based optical fibers has garnered interest in development of high performance single fiber lasers and other optical devices that benefit from the grating being formed in the fiber. However, silica fibers need to be short in length to prevent mode-hopping, and germano-silicate fibers have low pump absorption and suffer from ion clustering when the dopant concentration is increased. Phosphate glass fibers are much less prone to clustering and can be highly doped, but they are much less photosensitive, so that the conventional holographic side writing technique does not work well. In the past, creation of phosphate glass fiber lasers has meant splicing together fibers of different refractive indexes to create the laser cavity.
Applications:
- Communications
- Cutting and welding lasers
- Imaging systems
- Surgical lasers
- Dermal resurfacing
Advantages:
- Higher efficiency fiber lasers
- Short manufacturing time
- Excellent thermal stability
Status: Issued US Patent #8,077,747
Stage of Development: Prototypes have been fabricated.
