• Siddharth Ramachandran

    Siddharth Ramachandran is a distinguished professor of engineering at Boston University. He started his career in industrial research at Bell Labs, and his work with light-wave devices has helped advance optical networks, laser-based defense systems, brain imaging, and quantum computing.

    FIGURE 1. A signal enters a few-moded fiber used to obtain ultra-large-mode-area HOM propagation via the conventional, Gaussian-shaped fundamental mode, and is then converted to the desired higher-order mode with long-period fiber-gratings (inset on left shows the broadband, highly efficient nature of this mode conversion). After propagation (passive fiber) or amplification (rare-earth-doped fiber), the signal can exit in one of three conditions: the signal can be free-space propagated in the higher-order mode itself (top right), or converted to a Gaussian mode with a phase plate (middle right) or to another fiber grating (bottom right). Inset on the right shows that a module with input and output gratings can be achieved with less than 0.5 dB loss.
    Few-moded fibers in which a single higher-order mode is excited offer large mode areas, high bend tolerance, and the potential for dispersion tailoring.