Mid-infrared Spontaneous and Stimulated Raman Scattering in a Silicon Core Fiber

Compact and tunable light sources that can operate at wavelengths beyond 2 μm are of great interest for gas sensing and environmental monitoring. To this end, fibers that are doped with rare-earth cations, such as thulium and holmium, have emerged as contenders for wavelength emission from 1.9 to 2.1 μm. However, high power emission beyond 2.2 μmis challenging due to the need to switch from silicate to fluoride host glasses [1]. An alternative solution to extending the wavelength coverage is to make use of the efficient emission ~2 μmand shift the output to longer wavelengths via Raman scattering [2]. In this regard, silicon waveguides are a promising platform for Raman shifting processes due to their high damage threshold, strong Raman response and extended infrared transmission (1.1 ~ 7 μm). Moreover, silicon core fibers (SCFs) have recently emerged as a useful platform for Raman amplification that can offer low propagation losses and favorable propagation lengths compared to on-chip waveguides. As they are clad in silica, the SCFs are stable, and compatible with other glass fiber components, such as the pump laser, opening a route for the development of robust all-fiber systems [3].