Electrostriction in As2Se3-PMMA Microtapers [article]

Bhavaye Saxena, University, My, University, My
2019
Electrostriction is the tendency of materials to acquire a fluctuation in density in the presence of coherent electro-magnetic fields. It leads to a change in the refractive index of the material, which can be explained in the language of nonlinear optics as a consequence of third-order optical nonlinearities (known as Kerr nonlinearities). Such phenomenon is observed when intense beams, such as laser light, travel in a medium, e.g. an optical fiber, and the spontaneous scattering of the laser
more » ... ield from the thermally excited acoustic waves occurs. This effect, known as spontaneous Brillouin scattering, can become quite significant, giving rise to an interaction between the incident and backward reflected field (or the Stokes field), through the means of electrostriction. Such interaction can be classified under two categories of stimulated processes: (1) stimulated Brillouin scattering (SBS), in which two incident optical fields interact with longitudinal acoustic waves, and (2) guided acoustic wave Brillouin scattering (GAWBS), in which two incident optical fields interact with transverse acoustic waves. In case of SBS in optical fibers, the scattered light propagates backwards with a downshifted frequency of the order of GHz, while in case of GAWBS the scattered light propagates forward with multiple frequency shifts of hundred of MHz relative to the frequency of the pump laser. In this thesis, I demonstrate simultaneous generation of SBS and GAWBS from electrostriction of optical waves in a 60 cm As2Se3-Poly(methyl methacrylate) (or As2Se3-PMMA) microtaper waveguide. I show that the GAWBS in the microtaper couples with SBS through a complex energy transfer between weak Stokes and Anti-Stokes (AS) continuous waves in the presence of a high power pulsed pump wave. This results in an amplification of Stokes wave at 7.4 GHz, which is present in addition to a standard strong Stokes peak at 7.62 GHz and a secondary peak at 7.8 GHz that are contributed by SBS for a 2 micron As2Se3 core radius. The additional peak ar [...]
doi:10.20381/ruor-24032 fatcat:5r3lagp3ojbmbnvesmhyseabmu