Patent ID: 9716365
Date: 2017-07-25
CPC Classifications: G02B,H01S

Claim:
1. A fiber laser system comprising at least one fiber block configured with: an active fiber extending along a longitudinal axis and provided with concentric outer cladding and inner double bottleneck-shaped Nd-doped core which is operative to radiate a laser signal at a working wavelength and a parasitic wavelength; and at least one dumbbell-shaped coreless delivery fiber guiding pump light to the active fiber, the active and delivery fibers having respective axially coextending enlarged-area and reduced-area central regions which axially extend from respective input end regions, the active and delivery fibers being configured so that, for a shortest possible length of the active fiber and a given concentration of Nd dopants, a ratio between respective enlarged-area central core region and total clad area of the central regions of the respective active and delivery fibers is selected to provide the active fiber with a desired gain at the working wavelength and a preset gain at the parasitic wavelength, and the total clad area of the central regions and a total area of input end regions of respective active and delivery fibers are substantially equal to one another to provide for such a pump light absorption rate in the enlarged-area central region that the active fiber is structured with the shortest possible length which allows for the desired gain at the working wavelength and the preset gain at the parasitic wavelength; and a protective fiber sleeve surrounding the central regions of respective active and delivery fibers, the total clad area of the central regions of the respective active and delivery fibers being reduced at a coefficient at least equal to a ratio between numerical apertures of respective protective sleeve and delivery fibers.