Book Description
The creation of acoustic waves by light in optical fibers can be beneficial or detrimental in telecommunications depending on the application. In standard single mode fibers (SMFs), the generation of acoustic waves through Brillouin scattering is well understood. In photonic crystal fibers (PCFs), also known as microstructured optical fibers or holey fibers, however, the air holes, which run the length of the fiber and make up the inner cladding, disturb this process resulting in unique features. By understanding the effects of the parameters of PCFs, we can open them up to a wide range of applications. In this dissertation, I explore the effects observed in small-core photonic crystal fibers by stimulated and guided acoustic wave Brillouin scattering, which scatter light in the backward and forward directions, respectively. I have not only found a number of unique features in photonic crystal fibers but have gone further to explain their origins. In small-core PCFs, SBS exhibits a higher threshold and multiple backscattered peaks, neither of which is observed in standard single-mode fibers. These arise from the acoustically multimode nature of these fibers which leads to multiple acoustic modes being generated from a single optical mode, such modes having not only longitudinal components but also being coupled to torsional-radial waves and finally such modes extending into the cladding, leading to a weaker overlap with the optical mode and thus a higher threshold. I relate the origin of the polarization observed in the smaller core PCFs to small deviations from symmetry of the air holes closest to the core. The effect of such deviations is amplified by the small parameters (i.e. core diameter and lattice pitch) of the fibers. Finally, I further verify and extend a study of the trends of guided acoustic wave Brillouin scattering (GAWBS) in PCFs, as well as observe higher frequency torsional-radial, TR 2m , modes in two of the small-core PCFs which have not been observed in SMF.
