Resonant SRS Filtering Fiber for High Power Fiber Laser Applications

We explore the properties of a novel stimulated Raman scattering (SRS) filtering fiber for high average or high peak optical power delivery applications. The fiber geometry is based on a series of circularly arranged high index rods embedded in a leaky silica cladding. The operation principle relies on the resonant coupling of the core and rod modes and the wavelength-dependent leaking of the structure. The fabricated fiber demonstrated wide transmission window and filtering of SRS with extinction in excess of 20 dB at the Raman Stokes wavelength, excellent robustness with bending, and high output beam quality. The fiber has been tested as a beam delivery fiber of a commercial pulsed fiber laser system in order to explore the filtering performance and its limitations.