Laser-drawn silicon core fibers for nonlinear photonics

The linear and nonlinear properties of laser-drawn silicon core fibers (SCFs) are characterized in the telecom band for the first time. We show that the SCFs produced with micrometer-sized core diameters exhibit low optical losses (∼1 dB/cm) straight from the drawing tower, indicating a high-quality of the crystalline core materials. Moreover, by using an adapted fiber tapering method, the core diameter of these fibers can be precisely tailored to obtain longitudinal profiles optimized for low loss coupling, with uniform waist regions over lengths up to ∼7 cm and a further reduction in the linear losses to ∼0.2 dB/cm. Characterization of the nonlinear parameters reveals values in good agreement with previous measurements of single-crystal silicon. By exploiting the long lengths and low losses, an on–off Raman gain up to 9 dB was obtained when pumping with a continuous wave power of only <0.1 W. The high Raman gain achieved in this work highlights the potential of using these fibers for compact nonlinear signal amplification or laser systems.