Whispering gallery modes: advanced photonic applications
- Autores: Xavier Roselló Mechó
- Directores de la Tesis: Miguel Vicente Andrés Bou (dir. tes.), Martina Delgado-Pinar (codir. tes.)
- Lectura: En la Universitat de València ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Beatriz Ortega Tamarit (presid.), Antonio Diez Cremades (secret.), Gualtiero Nunzi Conti (voc.)
- Programa de doctorado: Programa de Doctorado en Física por la Universitat de València (Estudi General)
- Materias:
- Enlaces
- Tesis en acceso abierto en: TESEO
- Resumen
Whispering Gallery Modes (WGMs) based microresonators have attracted a great interest in the last decades due to their strong confinement of the light. Such microresonators can be fabricated with different geometries and materials. They exhibit high Q-factors and small mode volumes, which allows a great number of fundamental studies and applications, as for example the study of nonlinear phenomena. The narrow linewidths that the WGM resonances present enable the measurement of small perturbations of the microresonator parameters, with a low detection limit.
This thesis provides an experimental characterization of the properties of different optical fiber devices by means of WGMs. The operational principle is based on exploiting the tunability of the WGM resonances by means of variations in the parameters that define the material and the geometry of the microresonators. This feature enables the study of the microresonator properties by measuring the optical spectral position of the WGM resonances. The variation of the microresonator’s parameters can be induced by strain, a temperature change, or an external magnetic field. The characterization of the strain-optic effect in silica and PMMA axially stretched optical fibers allowed the determination of the strain-optic coefficients of both materials. Commonly, an axial strain generates a uniaxial anisotropy that can be measured directly with our approach. Analogously, the characterization of the thermo-optic effect in different optical fiber devices, illuminated with different optical signals, enables the measurement of a variety of parameters: the contributions of absorption and scattering to the loss coefficient in UV-irradiated photosensitive fibers, thermal profiles in long period gratings, and the heating induced optically in active doped fibers. The main features of the implemented experimental technique are its low detection limit, its spatial resolution, and its capability to perform the measurements in a broad range of optical wavelengths.
Locking techniques are necessary in experiments involving WGMs, to generate stable, nonlinear phenomena. This work provides two novel active locking techniques to stabilize the system at constant laser wavelength, which were experimentally tested. Both of them are based on the tuning of the spectral position of the WGM resonances either by means of axial strain, or temperature variations of the microresonators. Finally, optomechanical phenomena are a nonlinear effect induced by the high optical circulating power of the WGM, which results in the excitation of the acoustic modes of a microresonator. Vibrational resonant modes with high mechanical Q-factors were identified and characterized in bubble microresonators, and it was observed the transition to a chaotic behavior of this system, as the circulating power was increased.
