Optomecânica Brillouin integrada em materiais com baixas perdas

Author(s)

Roberto de Oliveira Zurita

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin
• Defense date: 2024-06-07

Examining board members

Thiago Pedro Mayer Alegre; Nathália Beretta Tomazio; Gilliard Nardel Malheiros Silveira; Lino Misoguti; Cleber Renato Mendonça

• Advisor: Thiago Pedro Mayer Alegre

Abstract

Stimulated Brillouin scattering (SBS) is an inelastic scattering phenomenon of light mediated by the acoustic waves in the medium. In this work, SBS is considered as an aspect of a broader field of optomechanical phenomena. From the point of view of the optical fields optomechanics can be understood as a non- linear interaction akin to three-wave mixing, which means that its intensity increases with optical power. Materials such as silicon suffer from Two-photon Absorption (TPA) and Free-carrier Absorption (FCA) which are non-linear loss channels that also increase with optical power. The competition with non-linear losses (FCA and TPA) limits the efficiency of SBS. In this work, we investigate two different platforms for integrated optomechanical devices: Lithium Niobate (LiNbO3) and Silicon Nitride (Si3N4). These materials are notorious for their optical power handling and small non-linear losses. We design two different device designs, one for each platform, exploring two facets of the broader optomechanical area: cavity optomechanics and waveguide Brillouin photonics. For LiNbO3 we design a ridge waveguide exploring its anisotropy to achieve acoustic guidance via Surface Acoustic Wave (SAW) and optimize the photoelastic coupling. For Si3N4 we design a circular optomechanical cavity that mimics a floating ring cavity by using a phononic mirror to isolate the outer ring from the anchored inner disk. Finally, we experimentally observe optomechanical coupling in both designs. Given the nature of each design, we employed different measurement techniques. Given the lack of a resonant optical cavity and small interaction length, we have to use a stroboscopic measure for the LiNbO3 waveguides. This measurement allows us to filter out the contribution from both linear and higher-order non-linear effects and measure just the signal that arises from the optomechanical interaction. This measurement setup allowed us to make the first measurement of Brillouin scattering in LiNbO3 (AU)

• FAPESP's process: 19/13564-6 - Optomechanics oscillators
• Grantee: Roberto de Oliveira Zurita
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)