Banca de DEFESA: RODRIGO GALVÃO DOS SANTOS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : RODRIGO GALVÃO DOS SANTOS
DATE: 30/06/2022
TIME: 09:00
LOCAL: Através de Videoconferência: https://meet.google.com/uan-jdak-ncu
TITLE:

Rare-earth-doped yttria nanoparticles as temperature sensors for whispering-gallery-mode resonators

KEY WORDS:

Yttrium oxide, rare-earth ions, nanothermometry, whispering-gallery-modes.

PAGES: 110
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

In this thesis, Y₂O₃ (yttria) nanocrystals (NC) doped with rare-earth ions, namely Nd³⁺ and Er³⁺,Yb³⁺ are investigated as temperature sensors for whispering-gallery-mode (WGM) resonators. The ions were chosen to match the available pump lasers for WGM coupling in a silica micropshere, so that multiple sensing parameters can be achieved with a single excitation wavelength. The silica micropsheres and the NCs used for this thesis have diameters of about 100 μm and 150 nm respectively. The much smaller size of the NCs with respect to the microspheres ensures that the thermal equilibrium remains undisturbed in the medium of interest (i. e., the microsphere) during the temperature measurements. In order to understand the effects of the lattice vibrations of host materials like yttria on the spectroscopic properties of the active ions, the concept of phonon by quantization of lattice vibration is introduced and the widths and positions of spectral lines of Nd³⁺ in Y₂O₃  are discussed as an example of the ion-phonon interactions following a Debye model. Moreover, the theoretical basis of WGMs coupling is derived from the modal equation for a microsphere and some simulations are performed for the system of interest. This system is then considered for temperature sensing applications and the effects of a near-field probe such as a nanoparticle close to the microsphere's surface are calculated using Rayleigh scattering. Some control experiments were also performed in order to optimize the experimental setup for WGM coupling using the microsphere-prism coupling geometry. A nanothermometer based on single Nd³⁺:Y₂O₃ NCs which relies on the ratio of thermally coupled emission lines is presented, followed by another yttria based system, Er³⁺,Yb³⁺:Y₂O₃. Both systems were characterized by exciting single nanoparticles with low power, continuous-wave lasers and the results were described by a rate equation model considering multiphonon interactions. Finally, some future experiments are proposed for the Nd³⁺:Y₂O₃ system, which showed promising results for temperature sensing for microresonators, taking into consideration the theoretical and experimental aspects for both the WGM and luminescence spectroscopy.

BANKING MEMBERS:
Presidente - 2199294 - LEONARDO DE SOUZA MENEZES
Interno - 1295016 - ANDERSON MONTEIRO AMARAL
Interno - 1133622 - ANDERSON STEVENS LEONIDAS GOMES
Externo ao Programa - 2199776 - RENATO EVANGELISTA DE ARAUJO
Externo à Instituição - CARLOS JACINTO DA SILVA - UFAL