Efficient Yb-doped air-clad fiber laser operating at 980nm and its frequency doubling

Yb doped fiber lasers are of importance due to their potential applications as efficient pumps for erbium doped fiber amplifiers, as well as for achieving the argon ion-laser line of 488nm through frequency doubling. An efficient high power fiber laser operating at 980nm is presented. The fiber laser consists of an all-silica air clad fiber with an Yb doped core. The double-clad fiber configuration has a single-mode (SM) core and a small diameter inner silica clad. The inner clad is surrounded by air filled capillaries within a standard sized outer silica cladding. The air cladding provides the fiber with high numerical aperture (NA), greater than 0.6. This high NA is essential for efficient pump coupling into the small inner clad, as well as for the fiber laser saturation and its resulted efficient operation at a three level scheme. Fiber Bragg gratings were written on the core, thus forming an all-fiber cavity. We have achieved over 1W of 980nm laser emission in SM, with a threshold of 285mW and a slope-efficiency of 30%. Furthermore, a very narrow line-width of the laser emission enabled its efficient frequency double using an extra-cavity doubling configuration with PPKTP crystals, developed by Soreq NRC. Output power of 19mW at 490nm in transverse SM has been achieved using a single polarization component of the fiber laser emission, with a conversion efficiency of 14%/W. All fiber cavity design within an all-silica air-clad fiber, and emission suitable for efficient frequency doubling makes this source highly suitable and cost-effective for various applications, such as telecommunication and diagnostics.