Compound Core Active Multimode Fiber for High-efficiency Fi

Altair Center proposes to develop a novel and innovative compound-core multimode active flber for high-efficiency fiber laser systems capable to operate in a single-mode regime. The compound multimode core of the fiber is especially designed in such a way to support propagation of a higher order mode exhibiting a sharp peak of its field in the central region of the core. The sharp-peak mode extracts energy form the entire volume of the active flber core and concentrates it in the core central region. The output beam is a well collimated waveguide mode which is almost diffraction limited and can be easily focused and coupled into a standard single-mode fiber. The compound-core fiber has many unique properties including the ability to operate at many different wavelengths simultaneously, wavelength selective and filtering properties, high sensitivity of the central mode peak to the external perturbations of the fiber, etc. This suggests its numerous applications in active and passive fiber based devices and sensors.In Phase I, the proposed concept will be proved analytically and experimentally. A technology for fabricating the compound-core fiber will be developed and the passive compound-core fiber will be characterized in detail. The active compound-core fiber and complete high-power eye safe fiber laser system will be fabricated and tested in the Phase II with the prototype system delivered to the USAF.