Semiconductor Optical Fibers for Nonlinear Applications

The nascent field of semiconductor optical fibers is attracting increased interest as a means to exploit the optoelectronic functionality of the semiconductor materials directly within the fiber geometry [1]. Compared to their planar counterparts, this new class of waveguide retains many of the advantageous properties of the fiber platforms such as robustness, flexibility, cylindrical symmetry, and long waveguide lengths. Furthermore, owing to the large Kerr nonlinearity of the materials, fibers with semiconductors embedded in the core are also ideal for the development of integrated nonlinear optical devices. In this paper we review our progress in characterizing the transmission properties of the semiconductor fibers and demonstrate their use in nonlinear applications. Particular focus will be placed on fibers with a hydrogenated amorphous silicon (a-Si:H) core as this material offers several favorable properties such as high nonlinear coefficients, low fabrication costs, and low transmission losses. Exploiting these features, we have demonstrated an array of nonlinear processes in the fibers including ultrafast optical switching, modulation and broadband continuum generation. Although many of the first generation semiconductor fibers have been fabricated with relatively large micron sized cores, by scaling these down towards the nanoscale dimensions used on-chip the nonlinear effects will be enhanced, paving the way for the development of low power, high speed all-fiber systems.