Structured Ytterbium and Erbium -doped Silica Fiber for Dual Wavelength Laser Operation
We report on a novel type of dual-wavelength fiber laser with a structured-core design inside silica glass, forming a spatial separation of the several core areas doped with ytterbium and erbium ions. We have optimised the key parameters of the fiber core, such as the concentration of rare earth elements, and the optimal length of active fiber to operate simultaneously at two different wavelengths. Using the Modified Chemical Vapor Deposition method to obtain initial optical fiber preforms, and using the stack and draw technique, we have fabricated two types of active fibers, one with 7 and one with 19 rare-earth-doped rods (elements) forming the fiber core. We characterized the drawn fibers by investigating their structure by scanning electron microscopy, confirming the spatial separation of the elements within the core. Measuring absorption shows that concentration ratios Nt Yb: Nt Er were approximately 52: 48 for 7 core fibers and 56:44 for 19 core fibers. Lifetimes for both active fibers were 0.84 ms for Yb3+ ion and 10.30 ms for Er3+ ion. The performance of fiber lasers was determined, proving that fibers are capable of laser emission simultaneously at 1042 nm and 1550 nm. We have shown experimentally that the output power ratio between both lasing wavelengths can be controlled by the length of the fiber.