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Quantitative phase imaging for surface roughness measurements to demonstrate variation of quality factor in crystalline whispering-gallery mode resonators (Conference Presentation)
Author(s): Maxime Jacquot; Guoping Lin; Aurélien Coillet; Souleymane Diallo; Laurent Larger; Yanne Chembo
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Paper Abstract

An experimental study of the variation of quality factor (Q-factor) of mm-size whispering-gallery mode (WGM) resonators manufactured with fluoride crystals as a function of surface roughness is proposed. Q-factors of the order of 1 billion are measured at 1550 nm. The experimental procedure needs repeated polishing steps, after which the surface roughness is measured by quantitative phase imaging, based on a white-light phase-shifting interferometry approach, while the Q-factors are determined using the cavity-ring-down method. This process allows us to reach an explicit curve linking the Q-factor of the disk-resonator to the surface roughness of the rim. The variations of Q-factor as a function of surface roughness is universal, in the sense that it is globally independent of the bulk material under consideration. We used a white-light interferometer to investigate the dependency of Q-factors considering three different difluoride crystals as bulk materials; in all cases, we have found that a billion Q-factors at 1550 nm are achieved when the rms surface roughness has a nanometer order of magnitude. We have also compared our experimental data with theoretical estimations. This comparison enabled us to highlight a mismatch, which can be explained by the many physical constraints imposed by the mechanical grinding and polishing protocol. We expect that our work will contribute to a better understanding of the Q-factor limitations for mm-size WGM resonators, which are finding applications in a broad range of areas.

Paper Details

Date Published: 4 March 2019
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Proc. SPIE 10925, Photonic Instrumentation Engineering VI, 109250N (4 March 2019); doi: 10.1117/12.2509408
Show Author Affiliations
Maxime Jacquot, Institut Franche-Comte Electronique Mecanique Thermique et Optique (France)
Univ. de Franche-Comté (France)
Guoping Lin, Huazhong Univ. of Science and Technology (China)
Aurélien Coillet, Lab. Interdisciplinaire Carnot de Bourgogne (France)
Univ. de Franche-Comté (France)
Souleymane Diallo, Institut Franche-Comte Electronique Mecanique Thermique et Optique (France)
Univ. de Franche-Comté (France)
Laurent Larger, Institut Franche-Comte Electronique Mecanique Thermique et Optique (France)
Univ. de Franche-Comté (France)
Yanne Chembo, Institut Franche-Comte Electronique Mecanique Thermique et Optique (France)
Georgia Tech - CNRS (United States)


Published in SPIE Proceedings Vol. 10925:
Photonic Instrumentation Engineering VI
Yakov G. Soskind, Editor(s)

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