Nonlinear optical properties of polycrystalline silicon-germanium core fibers from telecom wavelengths into the mid-infrared spectral region

GHOSH, AMAR NATH, Huang, Meng, Hawkins, Thomas W, Ballato, John, Gibson, Ursula J and Peacock, Anna (2024) Nonlinear optical properties of polycrystalline silicon-germanium core fibers from telecom wavelengths into the mid-infrared spectral region. Dudley, John M., Peacock, Anna C., Stiller, Birgit and Tissoni, Giovanna (eds.) In Nonlinear Optics and its Applications 2024. vol. 13004 (doi:10.1117/12.3017163).

Abstract

Polycrystalline silicon germanium (SiGe) core fibers offer great potential as flexible nonlinear platforms. Compared to Si core fibers, the SiGe material offers higher nonlinear coefficients, extended mid-infrared wavelength coverage, and the possibility to tune the bandgap and index of refraction through varying the Ge concentration. Here SiGe core fibers with 10% Ge were fabricated using the molten core drawing method, followed by CO2 laser irradiation. The transmission properties of the fibers were subsequently improved further using a fiber tapering method, to tailor the core diameter and enhance the crystallinity. The resulting tapered SiGe fiber had linear losses of 2.17 dB cm ^-1 at 1.5 µm and 4 dB cm ^-1 at 2.5 µm, significantly lower than previous reports. Nonlinear characterization of the fibers reveals that the nonlinear coefficients are higher than standard Si core fibers, as expected due to the introduction of germanium. The significantly higher value of the nonlinear figure of merit calculated for the SiGe fiber for wavelengths above 2 µm indicates that this new fiber platform could find numerous applications in mid-infrared nonlinear photonics.

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Contributors

Author: AMAR NATH GHOSH

Author: Meng Huang

Author: Anna Peacock

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