Single-Frequency Fiber Amplifier with Distal Cladding Stripper

Fiber lasers are devices that emit a beam of light concentrated in an optical fiber, a revolutionary development in laser technology. They cover a wide range of applications, but stimulated Brillouin scattering (SBS) has limited the maximum power for fiber lasers with narrow linewidths. SBS happens when power crosses a threshold, a scenario that is restricting the full potential of fiber lasers. The essence of the problem lies in the SBS limit on fiber lasers, with inefficient use of pump light and issues with beam quality acting as additional constraints. Current laser systems struggle to utilize all the absorbed pump light and reduce the length of the unpumped gain fiber at the output, and their designs do not optimally manage the beam area divided by the effective fiber length. Thus, these limitations highlight the need for improvements in fiber lasers technology.

Technology Description

The fiber lasers are designed to operate at higher stimulated Brillouin scattering (SBS) power thresholds. The technique includes the use of high-absorption gain fibers, operation at low pump absorption levels, reduction of the length of unpumped gain fiber at the output, and omission of a delivery fiber and cladding light stripper at the output. Additionally, free-space dichroic mirrors are employed for separating signal light from unabsorbed pump light, and cascaded gain fibers with nonoverlapping Stokes shifts are used. What differentiates this technology from other fiber lasers is the complexity of the techniques used. The lasers have been designed with a high-absorption gain fiber and follow up with a smaller diameter to improve beam quality. This upgrade in the fiber lasers enables an upper limit to their power, given that SBS occurs only when the power exceeds a designated threshold. By augmenting SBS power thresholds, these fiber lasers can deliver superior maximum powers at kilohertz-class linewidths.