Experimental Study of the Structural Dependence of Stimulated Raman-Like Scattering in Solid-Core Photonic Crystal Fibres

The tight confinement of both optical and acoustic fields in their μm-sized fiber cores of photonic crystal fibers (PCFs) can lead to enhanced Brillouin light scattering in the forward direction, which is well-known as the stimulated Raman-like scattering (SRLS) [1]. In general, the gain spectra of SRLS in PCFs are dominated by the PCF-core sizes, while their exact dependences upon the surrounding hollow-channels have not been systematically studied in experiments. In this work, we investigated a series of PCF samples with varied air-filling ratios <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$a$</tex><inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</inf>, and unveiled several key impacts of the PCF air channels upon their gain spectrum in terms of the gain strength, the frequency shift and multi-peak structure, together with physical interpretations of the underlying mechanism.