Opto-thermal Effects in WGM Microresonators

Author(s)

Victor Antonio Siqueira Marques

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 2024-07-23

Examining board members

Cleber Renato Mendonça; Gustavo Foresto Brito de Almeida; Leonardo De Boni; Paulo Henrique Dias Ferreira; Thiago de Souza Pinto

• Advisor: Cleber Renato Mendonça

Abstract

There is great interest in systems involving microresonators, due to the diverse areas of application, which makes studying the behavior of these devices important. When there is light coupled into Whispery Gallery Modes (WGM) microresonators for quality factors greater than 103, nonlinear thermal and optical effects may occur. These effects can vary the resonance wavelengths of the cavity and shift its spectrum. Therefore, the quantitative prediction of these effects and their consequences on the coupling of light inside microresonators can help in the development of integrated photonics technologies. The effects generated by the coupling of light are not instantaneous and therefore, the system with coupled light tends to transit through intermediate states until finding a point of equilibrium or a stable oscillation around it. A stationary theoretical model was then developed to analyze the equilibrium in opto-thermal dynamics. The model was based on previous studies, however, it started to take into account all the effects that were shown to be important, including even extra thermal sources, based on the experimental methodology that was used. An analysis of the stability of the system was also carried out at the equilibrium points found and an analysis of the validity range of the main equations was deduced. Through this stationary theory, some predictions were made, such as the maximum temperature for equilibrium, the average shift in the spectrum and the transmission variation with the coupled wavelength. These predictions were proven experimentally and with data from other studies. Finally, a simplified dynamic model was created using the developed stationary model and other studies as a basis, so that numerical- computational solutions proved to be more effective. The analysis in the phase plane demonstrated the validity of the stationary model, in addition to allowing the visualization of the dynamics through limit cycles around the stable equilibrium points, towards which the system tends, so that the stationary theory proved to be a usual simplification of opto-thermal dynamics. (AU)

• FAPESP's process: 20/09022-0 - Design and modeling of polymeric photonic microstructures
• Grantee: Victor Antonio Siqueira Marques
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)